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On the movements & habits of climbing plants by Ch. Darwin F.R.S. F.L.S.

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Table of Contents

Introduction Twining plants Axial Twisting Nature of the reaching movement} Purpose of the reaching movement & manner of the spiral ascent} Table of the ratio of Revolution} Anomalous revolvers variation in the power if twining} Leaf Climbers Clematis Tropæolum Antirrhineæ Solanum Fumariaceæ c Cocculus Gloriosa — Flagellaria Nepenthes Summary on Leaf- Climbers}

p. 1 p. 2 p. 9 p. 14.   p. 20     p. 35.   p. 44 p. 48.     p. 51. p. 69 p. 78 p. 81 p. 84 p. 86 86 89 90 90

Tendril Bearers Bignoniaceæ Polemoniaceæ Leguminosa Compositæ Smilaceæ Fumariaceæ Cucurbitaceæ Vitaceæ Sapindaceæ Passifloraceæ Spiral contraction of Tendrils} Summary on the nature & action of Tendrils} Hook-climbers — Root climbers Concluding Remarks on Climbing Plants}

p. 94. p 95 p. 116 p. 125 p. p. 131 p. 135 p. 138 p. 147. p. 165 p. 166 p. 170   185 p. 200 p 201 p. 204

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I was led to this subject by an interesting, but too short paper by Prof. Asa Gray on the movements of the tendrils of certain some Cucurbitaceous plants.*(a) My observations were nearly more than half completed before I became aware that the surprising phenomenon which struck of the spontaneous revolutions revolving by movements of revolutions of the stems & tendrils of twining climbing plants & of the tendrils of climbi of climbing plants had been long ago observed by Palm and by Hugo von Mohl, (1)*Ludwig Palm; & had been subsequently more recently the subject of two valuable memoirs by Dutrochet.* (c) Nevertheless, I hope believe that my observations, with due omissions will be found to contain sufficient novelty to justify me in laying then before the Linnean Society.).

(Climbing plants may be conveniently though not scientifically* divided into those which spirally twine

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*Proc. american acad. of arts & Science vol. IV. Aug. 12th 1858 p. 98.—

(The second note * has not been sent—)

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round a support; those which ascend by the movement of the foot-stalk, foot-stalk or the tips of their leaves; & those which ascend by true tendrils; these tendrils being either modified leaves, or flower-peduncles or perhaps other organs branches.

But these di sub division, as we shall see, all gr nearly all graduate into each other.

There are two other distinct classes of climbing plants, namely those which are furnished with hooks, such as r & those with rootlets; but as such plants exhibit no special movements, we are not here but little concerned with them; & when I speak of climbing plants they may be understood to be excluded. I refer to I refer exclusively to the first great class.

(Spirally Twining plants.)

This is the largest class sub-division, & it is, as we shall see, apparently the primordial & simplest condition of the class. My observations will be best given My observations will be best given by taking a few special cases. When the shoot from of a Hop (Humulus lupulus) first first rises from the ground, the two or three first-formed internodes are straight & remain stationary; but the next, when whilst very

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young & small small, may be seen to bend to one side & & to point to travel slowly to round towards all points of the compass, moving like the hands of a watch with the sun. The movement so quickly very soon acquire its its full ordinary rapidity velocity. From seven observations made in during August on shoots proceeding from the a plant which wa had been cut down, & on another plant during April, the average rate of revolution was during hot weather & during the day was was 2°, 8'; for each revolution; & none of the revolutions varied much from this rate. The revolving movement continues as long as the plant continues to grow; but each separate internode, as it grows old, ceases to move.) (To ascertain more precisely what amount of movement each internode was capable of, underwent, I kept a potted plant in a pot in my room, in a well-warmed room to which I was confined during the night & day. A long inclined shoot was revolving projected in an inclined direction, beyond the point upper end of the supporting stick, round which the stem was twined, & & was steadily revolving. I then took a longer stick & tied up the shoot, so that only a very young internode, only 1 3/4 of an inch in length, in was left free. this certainly revolved moved moved during the day, but was so this was so nearly upright that its

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revolution could not be easily observed; but it certainly moved, & the stem side of the internode which was at one time convex became concave, which, as we shall hereafter see, is a sure sign of the revolving movement. The next day the little I will assume that it made at least one revolution, easily the next morning during the first 24° hours. Early the next morning its position was watched marked & it made a second revolution in under 9°: during the latter part of this revolution it moved moved much quicker, & the third circle was performed late in the evening in a little over 3°. As on the succeeding early early morning I found that the shoot revolved in 2° 45'; thu it must have made during the night four revolutions at each at the average rate of a little over 3°; I should add that the temperature of the room varied only about very little. The next or ninth revolution was effected in 2° 30'; The shoot had now grown to a l 3 1/2 inch in length & borders carried at its extremity a young internode one inch in length, which showed slight changes in its curvature curvature. From this time forward, the revolutions were carefully & easily observed. From this time forward, the revolutions were easily observed. The last made, was the thirty-seventh; but this

The 36th thirty-sixth revolution was performed at the usual rate; so

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was the last or thirty-seventh, but it was not quite completed; for the internode abruptly came to the centre became upright, & came moving to the centre, & was remained motionless. I tied a slight weight to it's the aupper end of the internode, so as to slightly bow it & thus to detect detect any movement; but there was none (a).)

(A few more remarks will complete all that need be said on this one internode. & we shall thus gain a fair action of the

It moved during five days; but the regular & more rapid movements, after the third revolution, lasted only only during three days and twenty hours. The regular revolutions from the ninth to thirty-sixth inclusive were performed at the average rate of 2° 31'; but the weather was cold, especially dawn & this affected the temperature of the room, especially during the night, & consequently ret retarded a little the rate of movement. There was only one irregular movement, after when a seri segment of a circle was rapidly performed (not counted in above enumeration) & this occurred

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(a) text

Some time before the last revolution, the lower lower part of the internode had apparently ceased to move.)

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after an unusually slow revolution of 2° 49'.

After the 17th revolution, our the internode had grown from 1 3/4 to 6 inches in length, & carried an internode 1 7/8 inch long, which was just perceptibly moving & this carried a very minute in ultimate internode.

After the 21st revolution the penultimate internode was 2 1/2 inches long & will have probably revolved in a period of about three hours. After At the 27th revolution our lower internode was 8 3/8 long, the penultimate 3 1/2 & the ultimate 2 1/2 inches in length; & the inclination of the whole shoot was such, that a circle 19 inches in diameter was nowswept by it. When the movement ceased the lower internode was 9 & the penultimate 6 inches long in length. So that from the 27th to 37th revolutions inclusive, three successive internodes, one on each other, were at the same time revolving. When the nature of the movement is explained, we shall see how this is for the result of this

(The lower internode, when it ceased revolving became upright & rigid rigid; but as the whole shoot grew to its weight continued to grow without any support it became nearly horizontal from its weight; the

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uppermost & growing internodes still revolving at the extremity; but of course no longer round the old centre central point of the supporting stick.

The From the change in the position of the centre of gravity of the revolving extremity, a slight & slow swaying movement was given to the long p &horizontally projecting shoot, & which I mistook for some time at first for spontaneous movement.

As the shoot grew, it depended more & more, whilst the growing & revolving extremity turned itself up more & more.

With the Hop, we have seen that that three internodes were at the same time moving revolving; & this was the case with most of the plants observed by me. With all, if in full health, two revolved; so that by the time one ceased, that above was in full action, & a terminal internode was just commencing to revolve. commencing the revolving

With Hoya carnosa, on the other hand,

several internodes [text pasted over]

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Thus I had

a depending shoot, thirty-two inches long, without any developed leaves, & consisting of six seven internodes, (a minute terminal one, an inch in length, being counted), continually, but slowly, swayed from side to side in a semicircular direction course, with the extreme point internodes making a complete revolutions: this swaying movement was certainly due to the movement of the lower internodes, which had not however force sufficient to swing the whole shoot round the central supporting stick. The case of another Asclepiadaceous plant, viz Ceropegia Gardnerii, is worth briefly giving: I allowed the tip to grow out almost horizontally to the length of 31 inches; this now consisted of three long internodes, surround terminated by two short ones: the whole revolved in a course opposed to the sun (the reverse of that of the Hop) at rates between 5° 15' and 6°. 45' for each revolution. Hence the extreme tip made a circle of above five feet (or 62 inches)

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For instance with: a shoot of Ceropegia Gardnerii projected beyond the supporting stick & revolved at the rate of      per circle, moving against the sun, in the reversed direction compared with the Hop. I allowed this shoot to grow till it

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in diameter or and sixteen feet in circumference, & so thatthe tip travelled at the rate about the average rate the rate (assuming the circuit to have been completed in six hours) of 32 or 33 inches per hour. I regret I did not observe whether the shoot would have gone on revolving when grown to a still greater length. It was an almost

the plant stood on

The weather being hot the plant was allowed to stand on my study table, & it was an interesting spectacle to watch the long shoot sweeping, night & day, this grand circle, as if in search of some object to cla round which to twine.

(If we take hold of a young growing sapling, grow we can of course bend it so as to make its tip describe a circle, like that performed described by the tip of a spontaneously spontaneously moving twining revolving plant.

By this movement the sapling is not in the least twisted on round its own axis: I mention this because if a black point be painted on the upper si back, on the side

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which is uppermost when the sapling is bent towards the holder's body; as the circle is described, the black point gradually goes sinks turns round & sinks to the lower side, & comes again comes when the circle is completed upper to the upper side & this gives the false appearance of twisting, which with with revolving in the case of spontaneously revolving plant deceived me for a time. The appearance is the more deceitful, because all the axes of all nearly all (as fat as I have seen) twining plants is are really twisted; & they are generally (if not in twisted in the same direction with the spontaneous revolving movement. To give an instance,— the internode of the hop, at of which the movements history has been evidently described recorded, was at first, as could be seen by the ridges on its surface, not in the least twisted; but when, after the 37th revolution, it had it had grown nine inches long & its revolving revolving movement had ceased, it was had become thrice twisted three times round on its own axis, in the line of

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[illeg]. But by far the best evidence of the twisting does not cause the revolving movement is afforded by many leaf-climbing & tendril-bearing plants, of which the internodes are not regularly twisted (for instance as with the case ofPisum sativum, Echinocystis lobata, Bignonia capreolata, Eccremocarpus Eccremocarpus scaber; & with the leaf-climbers, Solanum jasminoides & various species of Clematis) &, but which regularly perform, as we shall hereafter see, reg revolving movements like those of true twining-plants)

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movement course of the sun; on the other hand, the kidney-bean common convolvulus which revolves in an opposed course to the Hop, was likewise becomes twisted in an opposite opposed direction.

(Hence it is not surprising that Hugo von Mohl (s. 105, 108 &c) thought that the twisting of the axis caused the revolving movement: I cannot fully understand how he supposed that in the one movement is supposed to cause, causes the other; but it seems is scarcely impossible that the the twisting of the axis of the hop only three times rounded on itself could have caused thirty-seven revolutions.

Moreover the revolving movement commenced in the young internode of the hop, before any twisting of the axis could be detected; & the the internode of a young Siphomeris or Lecontea revolved (sp ?) revolved had grown to a considerable length & had revolved many times, before it during several days & then became twisted, only once on its own axis & then only in a slight degree. Again I observed a shoot of a hop which had spirally wound round a stick standing only 3/4 of an inch from another stick, so that the shoot could

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of true twining plants. Moreover according to Palm (s. 14) (s. 30, 95) Mohl (s. 149) & Léon* (p. 3 an internode may occasionally, & even not very rarely, be found, which are twisted in an opposite direction to the other internode on the same plant & to the course of revolution; & this according to the Léon*(p. 356) is always the caseall the internode of a variety of the Phaseolus multiflorus. Internodes which have become twisted round their own axes, if they have not ceased revolving are still capable of twining, as I have several times observed.)

(Mohl has remarked (s. 111) that when the a stem twines round a smooth cylindrical stick it does not become twisted. Accordingly I allowed kidney-beans to run up stretched strings & rods of iron & glass one-third of an inch in diameter, & they did not became twisted only in that degree which follows as a mechanical necessity from the spiral winding. The stems, on the other hand, which had ascended the ordinary rough sticks, were all more or less & generally much twisted. The

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Foot-note

*a Bull. Bot. Soc. de France Tome V. 1858 p. 356

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f influence of the roughness of the support in causing axial twisting was well seen in the stems which had twined up the glass rods; for these rods were fixed below to a spl in a split stick below, & were secured above to cross sticks, & the stems in passing these places had become very much twisted. As soon as The the stems which had ascended the iron-rods reached the summit & became free, they also became twisted; & this apparently occurred more quickly during windy weather. Several other facts could be given showing that the axial twisting stands in some relation to the inequalities in the support & likewise to the shoot revolving freely without any support. Many plants, which are not twiners, become in some degree twisted round their own axes;*a, but this occurs so much more generally & in so marked a manner with twining plants, that

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that there must be some connection between the act of capacity for twining & axial twisting. The most probable view, as it seems to me, is that the stems twist itself themselves to gain rigidity, in the same principle as that a much twisted rope is stiffer than a slackly twisted one, so as either to pass over inequalities or to support itself in their spiral ascent or to carry themselves their own weight when forced allowed to revolve freely.)

(I have just alluded to the twisting which necessarily follows from the spiral winding of the stem; namely are a twist once round the axis for each spire completed. spire This was well shown by painting a straight lines on living stems, and then allowing them to twine.

But, as I shall have to recur to this subject when under Tendrils, it may be here passed over.)

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*(a) Professor Asa Gray has remarked to me in a letter that in Thuja occidentalis the twisting of the bark is very conspicuous.

The twist is generally…. to the right of the observer; but in noticing about a hundred trunks, four or five were observed to be twisted in an opposite direction.

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axis, which same [text excised] so so undergone general

these in comparison with other plants. What this connection is was twining plants, & this spiral twining habit do not know; but it may I suspect that be related to the following circumstance: the connection is as follow:

Every twining stem in twining from mechanical necessity, as will presently be explained, must be twisted once round its own axis for every complete spiral,— unless indeed the planted [text excised] times twisting twisted itself in

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(I have compared the revolving movements of a twining plant to that of the top tip of a sapling moved round & round by the hand held some way down the stem; but there is a most important difference. The upper part of the sapling moves as a rigid body & remains straight; & but with twining plants every inch of the revolving shoot which is revolving is in motion has its own separate & independent movement. This is easily proved; for when the lower half or two-thirds of a long revolving shoot of any plant is revolving quietly tied to a stick, the upper free part alone steadily goes on continues revolving: if however, even if the whole shoot, except the terminal tip of an inch or two in length be tied up, this tip, as I saw have seen in the case of the Hop, Ceropegia, Convolvulus, &c, goes on revolving, but slowly much much more slowly for than the ordinary rate, from very the young the internodes, do whilst very young, until they have grown grown to some little length, always move slowly. very slowly. It is not difficult to understand the nature of the movement which is in fact

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a simple self beading of the whole length of the shoot, successively directed to all points of the compass. If we look to the one, two, or several internodes of a revolving shoot, they will be all seen to be more more or less bowed, either either during either either the whole period of revolution or durin during a large part of each revolution. Now if a coloured line streak be painted (this was done with a large number of twining plants) along, we will say, the whole convex line of surface, this coloured streak will after a time (depending on the rate of revolution) will be found to lie along one lateral margin side of the bow, & then along the concave side, again then on the opposite side & ulti lastly again on the originally convex surface. This clearly shows proves that during the internodes during the revolving movement become bowed in all all every every direction. This coloured streaks observations were made on the revolving internodes The movement is in fact a continuous self-bowing of the whole shoot

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successively directed to all points of the compass) (As this movement is rather difficult to understand, it will be well to give an illustration: if we let us take the tip of a growing sapling & bend it to the south & then paint a black line on the convex surface; let the sapling spring up & bend it to the east, the black line will now be seen on the northern lateral face lateral face one one side (facing fronting the north) of the shoot; bend it to the north, the black line will be on the concave side surface; bend it to the west, the line will be on the opposite side southern lateral face, & when again bent to the south the line will again be on the original convex surface. Now instead of bending the sapling let us suppose that the cells on the its whole southern surface side face side of the shoot to contract from the base to the tip to contract, & the whole shoot will be bowed to the south; then let the whole

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longitudinal contracting surface from the base to the tip slowly creep from the southern to the eastern side round the shoot, deserting by slow degrees the southern side by degrees & encroaching on the eastern side, & so round by the north, & west by the west again to the south; again; in this case the point of the shoot will be remain always bowed with the painted line appearing on the convex, two lateral, 2 concave 2 surfaces, 2 with the point of the shoot successively directed to all points of the compass. & will In fact we should thus have the exact kind of movement seen in the revolving shoots of twining plants. I have spoken in the illustration for brevity sake of the cells along each face successively contracting; of course turgescence of the cells on the opposite face, or both faces combined, would do equally well.­—

(It must not be supposed that the revolving revolving movement of the twining plants are is as so regular as given that given in my illustration. In very many cases the tip describes an ellipse, even a

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very very narrow ellipse: to recur once again to our illustration, if we suppose the southern & then the northern face of the sapling to contract & then the,the summit would would will describe a simple arc; if the contraction first travelled a very little to the eastern face & during the return a little to the western face, an a narrow ellipse would be described; & the sp sapling would be straight as it passed to and fro by the central point. A complete straightening of the shoot may often be observed in revolving plants; but the weight of the shoot apparently likewise interferes with the point regularity of the movement, & with the place of straightening.

The movement is often, in appearance at least, as if the southern, eastern & northern faces had contracted, but not the western face, so that a semicircle is described, & the shoot becomes straight & upright in one part of its course.

When a revolving shoot consists of several internodes, the lower ones several lower ones bend at the same rate & act as if one; but the one or two terminal internodes bend to all points

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at a slower rate; hence the movement do not concur, & that though at times the internodes may be bowed in the same line, at other times the shoot is rendered slightly serpentine, as I have often observed. The rate of movement of revolution of the whole shoot if judged by the movement of the extreme tip, is thus also likewise at times accelerated or retarded. One other point may must be noticed: authors authors have observed that the extr end of extremity extremities of points end of the shoot of many in many twining plants is completely hooked; this is very general for instance with the Asclepiadaceæ. & it apparently is of some service to the plant by in in hooks catching a support.

The hooked tip in all the cases which I observed, viz in Ceropegia Gardnerii, Sphærostema, marmoratum Clerodendron, glycine, Wistaria, Stephania, Akebia, & Siphomeris, has exactly the same kind of movement as the other revolving internodes; for a line painted on the convex outline surface becomes lateral & then

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concave; but, owing to the youth of these terminal internodes, the reversal of the hook took takes more time is a slower process than that of the revolving movement. (a) The more abrupt bending or hooking of the terminal internodes being so much more abrupt than that of the lower internodes, is, I presume, due to their youth & greater flexibility. In Lonicera brachypoda the hook only straightened itself periodically, & never becomes reversed. I will not assert that when the hooked tips of all all twining plants when is hooked, make as above described; for this from position may perhaps in some cases be due to the manner of growth, as in the case with the always bent tips of the shoots of the common vine & more plainly with those if Cissus discolor; which these plants however are not spiral twining plants twiners.)

The purpose of the spontaneous revolving movement, or more strictly, as now described, of

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a) This strongly marked tendency in terminal & flexible internodes to bend more abruptly than to the other internodes is of service to the plant; for not only does the hook thus formed sometimes serve to catch a support, but (& this seems to be much more important) it allows causes the extremity of the shoot to embrace much more closely its support than it otherwise could have done; & thus aids in preventing it the stem from being blown away during windy weather, as I have many times observed.

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the continuous bending movement successively directed to all points of the compass, is, as Mohl has remarked, obviously to allow the plant shoot to find a support. The plant beautifully gains its this end by perseveringly revolving night & day, revolving, sweeping, and as the shoot increases in length, a low wider & wider circuit.

This is admirably effected by the revolutions carried on night & day, with a wider & wider circle swept, as the shoot grows increases in length. As we now understand the nature of the movement, we can see that when at last the shoot meets with a support, the motion at the point of contact is arrested; but all the free projecting part goes on revolving.

Almost immediately another another & upper point of the shoot is brought into contact with the support & is arrested; & so onwards to the extremity of the shoot. When the shoot follows the sun in its revolving course, it wound rou winds itself round the support from left rightto right left, — the climber with its

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support being supposed to stand in front of the beholder; when the shoot revolves in an opposite direction, the line of winding is likewise reversed. When any one internode had ceased to revolve, I have invariably found that it had entirely lost the power of spirally twining round a support. If a man swings a rope from right to left round his head, & the end meets hits against a stick, the end it will coil round the stick in a opposite direction, according in accordance with the that of the as he has swinging the rope; so it is with a twining plant, the continued contraction or turgescence turgescence of the cells along that free free of that free part of the shoot which projects beyond the arresting support shoot, from its base to the extremity, replacing the momentum momentum of each atom of the same free whole part point [illeg] revolving free end of the rope.—)

(All the authors, except von Mohl, who have discussed the spiral twining of plants maintain that such plants have a natural tendency to grow spirally. Mohl believes (s. 112) that twining stems

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have a dull kind of irritability, so that they bend towards any object which they touch. Even before Before reading Mohl's interesting treatise, this view had seemed to me so probable, & I tried tested it in every way that I could, but with negative results. I rubbed the many shoots much harder than is necessary to excite movement in any tendril or in the foot-stalk of any a leaf climber, but without any effect. I then tied a very light forked twig on the shoot of a Hop, Ceropegia, Sphærostema & Adhatoda, so that the fork pressed on only one point side of the shoot & revolved with it; in the case of the [illeg] but it produced no effect; I purposely selected some very slow slow revolvers, as it seemed most likely that these might require the aid of would profit from possessing irritability; but in no case was any effect produced. Hence I conclude that twining stems are not irritable; & indeed it is not probable that they should be so, as nature always economises her means, & irritability would clearly be superfluous. Nevertheless I do

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not wish to assert that in no they are never irritable; for the growing growing axis of the leaf-climbing, but not twining spirally twining Lophospermum scandens is, as we shall hereafter see, certainly irritable; but this case gives me confidence that ordinary twiners do not possess this quality, for immediately that I saw the effect produced by a directly after putting a stick to the Lophospermum, I saw that it behaved differently from a true twiner twiner.) or any other leaf-climber.)

(The belief that twiners have a natural tendency to grow spirally, probably arose from their assuming this course form when winding wound round a support, & from the extremity assuming even whilst remaining free, sometimes assuming this same form.

The free internodes of vigorously growing plants, when they cease to revolve rather suddenly become straight & show no tendency to be spiral; but when a shoot has nearly

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ceased to grow, or when the plant is unhealthy, the extremity does occasionally become spiral. I have seen this in a remarkable degree with the ends of the shoots of the Stauntonia & of the allied Akebia, which became closely wound up spirally, just like a tendril, especially after the small, ill-formed leaves had perished. The explanation of these facts is, I believe, that the lower parts of each these terminal internodes very gradually in & successively lose their loses its power of movement, whilst the part portions just above goes goes on moving, moves, & so onwards, move onwards & in its their turn become motionless; & this would end in forming an irregular spire.)

When a revolving shoot strikes a stick, it winds round it rather slower more slowly than it revolves. For instance a shoot of the Ceropegia which was revolving at about the rate of took 9° 30' to wind make one complete spire round a stick, whilst it revolved in 6°: Aristolochia gigas revolved in about 5°, but took 9° 15' to complete its spire.

This, I presume, is due to the continued

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disturbance of the moving moving acting force by its some arrestment at each successive points; we shall hereafter see that even shaking a plant always retards the revolving movement. The terminal internodes of a a long, a horizontally much-inclined revolving shoot of the Ceropegia, after they had begun to wind round a stick, soon stopped always gradually, but slipped up it, so as to render the spire more open than it was at first; & this was evidently caused by due to the moving force which causes the revolutions of the shoot, being now freed from the constraint constraint of gravity & allowed to act freely.

With the Glycine Wistaria, on the other hand, a long horizontal shoot wound wound itself at first into a very close spire, which remained [illeg] unchanged; & but subsequently as the shoot [illeg] grew & wound itself it made a a much more open spire. With many all the many plants which I observed, were allowed freely to ascend a support, [text taped over] the terminal internodes now spiral internodes made at first a close spire; & this during windy weather, serves to keep the shoots in close contact with their support; but as the penultimate internodes grow in length, they pushed themselves up for a considerable length space even over more than a semicircle (ascertained by coloured marks on the shoot & on the support) up & round the stick.)

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(It follows from this latter fact that the position occupied by each leaf with respect to the support in fact finally in large part depends on the growth of the internodes, after they have become spirally wound round it. themselves spirally I mention this on account of an singular observation by Palm (s. 34), who states that the opposite leaves of the Hop always stand exactly over over each other, in a row on the [text taped over] (a) (my gardener

same side of the supporting stick, though this may differ in thickness. & though My sons visited a Hop-field for me & reported that though they generally found the points of insertion of the leaves successive pairs of leaves exactly over each other for a space two or three feet in length height; yet that this never occurred up the whole length of the pole; but that the points of insertion forming, as might have been expected, an irregular spire. Any irregularity in the pole entirely put out the regularity of position of the leaves. From casual inspection, it appeared to me that the opposite leaves of Thunbergia alata were symmetrical arranged

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in a line up the sticks, round which they plant had twined: accordingly I raised a dozen plants & gave them sticks of various thicknesses & string to twine round; & in in this case one alone out of the dozen had its leaves arranged in a perpendicular line, so I conclude that there is nothing in remarkable in Palm's obser rem statement.)

(Twining plants, I may add before they have wound round a support naturally have their leaves placed)

(The leaves of twining plants are rise from the stem (before it has twined) either alternately or oppositely on or oppositely or in a spire; in the latter case, the direction of the spire of line of insertion of the leaves & that time of the twining the course of the revolution or twining coincide. This fact has been well shown by Dutrochet*a who found different individuals of Solanum dulcamara twining in opposite directions & these had their leaves spirally arranged in an opposite line direction. It is clear A dense whorl of many leaves would apparently be incommodious for a twining plant, & it has been said* (b) some authors have supposed that none have their leaves in a whorl thus arranged; but this would a twining Siphomeris from Kew has whorls of three.)

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(Having referred to the position of the leaves, I may add that Twining plants I may add have alternate, opposite

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Com*(a) Comptes Rendus 1844 Tom. 19 p. 295. and Annales des Sc. Nat. 3d series Bot. Tom. 2 p. 163.

[text excised]

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If a stick, which has arrested a revolving shoot, but has not as yet been as yet wound round, be suddenly taken away, the shoot generally springs forward, showing that it has continued to press against the stick. If after the stick, after shortly after having been wound round, be withdrawn, the shoot is retains for a time its spiral form; then straightens itself & again commences to revolve. The long nearly horizontal much-inclined shoot of the Ceropegia previously previously alluded to, offered some curious peculiarities. The lower & older internodes which continued to revolve, had become so stiff that they were incapable on repeated trials of twining round a thin stick support; showing that the power of movement is was retained, after flexibility had sufficient to twine round a stick had been lost & that I gradually then moved the stick till further from the centre of revolution, till the to a greater distance, so

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that it was struck by the end of a terminal point, two inches & a half in length a point two inches & a half from the extremity of the penultimate internode; & it was then neatly wound round by this part & by the ultimate internode: after leaving the spirally wound shoot for eleven hours I quietly withdrew the stick from a & in the course of the day the whole curled curled part straightened itself & [illeg] recommenced revolving; but the lower & straight part & not curled portion of the penultimate internode did not move,— a sort sort of hinge separating the moving & the motionless part of the same internode. After a few days, however, I found that this lower part had likewise recovered its revolving power. These several facts show that the arrested portion of a revolving shoot; the powers of movements are power of movements is not immediately lost, & that when temporarily lost it can be recovered. Ultimately it is quite lost, & the shoot retain a spiral form When a shoot has remained for a considerable time round shoot its support, it permanently retains a spiral form, when the support is removed.) form, when the support round which it had twined spirally wound, is has been removed.)

(When a stick was placed so as to

(31

arrest the lower & rigid internodes of the Ceropegia, at the distance at first of 15 & then of 21 inches from the centre of revolution, the shoot slowly & gradually slided up the stick, so as to become more and more highly inclined; then after an interval sufficient to have allowed permitted allowed of a semi-revolution, it suddenly bounded from the stick & fell over to the opposite side, to its ordinary slight inclination, It then now recommenced revolving in its usual course, so that after a semi-revolution it was again arrested by came into contact with the stick, again slided up it, & again bounded from it. This movement of the shoot had a very odd appearance, as if the shoot was it were disgusted with its failure, but was resolved to try again.

We shall, I think, understand this movement by considering the former illustration of the sapling, of in which the contracting surface was supposed to creep from the southern side by the eastern, to

(32

the northern, & thence back again by the western side side to the southern side face,— successively bowing the sapling in all directions. Now with the Ceropegia, the stick being placed a very little to the east of due south of the plant, the eastern contraction could produce no effect beyond pressing it against the stick; but as soon as the northern contraction on the northern face began, it would slowly drag drag the shoot up the stick; until and then as soon as the western contraction had had well begun the shoot would be drawn from the stick, & its weight coinciding coinciding with the now north-western north-western contraction would cause it suddenly to fall to the opposite side, into its proper slightly inclined position; & the ordinary revolving movement would go on.

I have described this case, because it first made me understand the nature of movement order in which the contracting or turgescent cells of revolving shoots acted. in with all ordinary revolving shoots.—

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(The view just given further explains, as I believe, a fact noticed observed by Mohl (s. 135) namely that a revolving shoot, though it will twine round the an object as thin as a thread, cannot do so round a thick support. I placed some long revolving shoots of a glycine in contact with a Wistaria close to a post between five & six inches in diameter, but they would not though aided by me in many ways, wound round it. This I seems caused by the flexure of the shoot, when in contact with winding round so thick an object so many feet gently curved as this post, not being sufficient to hold as by a hooks the shoot to its place, when the contacting side surface to the shoot; so that it is continually being at each revolution withdrawn from its support.)

& again coming comes into contact with it.—

(34

(When a shoot has grown beyond its support, it sinks from its weight, as already explained in the case of the Hop, with the revolving end always turning upwards. If the support be not lofty it will su fall to the ground, & then resting sides again for it, as a true & resting on it the extremity will rises again.

Sometimes several shoots, when flexible, will twine together into a cable, & thus support each other. Single Very thin depending shoots, such as those of the Sollya Drummondii, will turn abruptly back & wind upwards on themselves. (a) In other cases, as with the Cryptostegia grandiflora, several internodes in succession which originally were flexible & revolved, will in succession if they do not succeed in twining round a support, become rigi rigid & perfectly supporting themselves upright, & will carrying carry on their summits the younger revolving internodes.)

(Here will be a convenient place to give a Table, showing the direction & rate of movement of several twining plants, with a few

[34v]

(a). The depending shoots, however, of one twining plant, the Hibbertia dentata, has no such hardly any tendency to twine upwards.

(35

appended remarks. These plants are arranged according to Lindleys Vegetable Kingdom of 1853; & they have been selected from all parts of the great series to show that twining plants of all orders kinds behave in a nearly uniform manner.*

List of Twining Plants, not aided by tendril or by imitable leaf-stalk stalks.— (small type)

(Acotyledons)

Lygodium scandens (Polypodiaceæ) moves against the sun.

Jun 18th   — 19th     20'

1' circle 6° 2d do 6°.15 — late in evening 3d do 5° 32 4' — 5°} very hot day 5' 6°

Lygodium articulatum, moves against the sun.

July 19th 20' 21' 22'

1' circle 16° 30' shoot very young 2d do 15° 0' 3d 8° 0' 4 10° 30

(Mononcotyledons.)

Ruscus androgynus (Liliaceæ), placed in the hot-house, moves against the sun.

May 24th   — 25 — —

1' circle in 6° 14' (shoot very young) 2d circle 2° 21' 3d do 3° 37' 4 do 3° 22'

May 26th — 27 — do

5'' circle in 2° 50' 6'' do 3° 52' 7" do 4° 11

 

[35v]

*I am much indebted to Dr. Hooker for having sent me many plants from Kew; & to Mr. Veitch of the Royal Exotic nursery for having generously given me a large collection of fine specimens of climbing plants. Professor Asa Gray and Oliver have afforded me, as on many previous occasions, much information & many valuable references.—

(35 bis

Tamus communis (Dioscoreaceæ)— a young shoot from a potted tuber in a pot in the greenhouse; follows the sun.—

July 7th do — 8'

1st circle in 3° 10' 2d do 2° 38' 3d do 3° 5'

July 8' do do

4'' circle 2° 56' 5'' circle 2° 30' 6'' circle 2° 30'

 

Lapagerea rosea (Philesiaceæ), in greenhouse, follows the sun.

March 9th March 9th — 10th — 11 — 12 — 13 — 16

1st circle 1' circle do shoot young 1' circle 26° 15' shoot young semicircle 8° 15 2d circle 11° 3d — 15°. 30' 4'' 14° 15' 5 8° 40' placed in hot-house: the next day the shoot remained stationary. to whole next day.—

(36

Roxburghia viridiflora (Roxburghiaceæ) moves against the sun; it travelled a circle in about 24°.

(Dicotyledons.)

Humulus Lupulus (Urticaceæ) follows the sun;

April 9th Two circles in 4° 16'

Young shoot from a cut down plant

April 9th

Aug. 13th — 14 — —

3d circle 2° 4th. do 2° 20' 5th — do 2° 16' 6th do 2° 2' 7th do 2° 8th do 2° 4'

a plant placed in a room;

April 9th A semicircle, travelling from window light, was performed in 1° 33'; travelling to the light in 1° 13'; difference of rate 20'

Akebia quinata (Lardizabalaceæ), placed in hothouse; moves against the sun.—

March 17th — 18 — 19'

1s circle 4° 0' (shoot young) 2d do 1° 40' 3d do 1° 30' 4th do 1° 45'

Stauntonia latifolia (Lardizabalaceæ), placed in hothouse, moves against the sun.

March 28' — 29

1s circle 3° 30' 2d do 3° 45.'

(37

Sphærostema marmoratum (Schizandraceæ) follows the sun.

Aug 5 circle in about 24° — second circle in 18° 30'

Stephania rotunda (Capparidæ Menispermaceæ) moves against the sun.

May 27, — 30

1st circle 5° 5' 2d do 7° 6'

June 2d— 3d

3d circle 5° 15' 4th do 6° 28'

Thryallis brachystachys (Malpighiaceæ) moves against the sun: one shoot made a circle in 12° another in 10° 30'; but the next next day, which was much colder, it took the first shoot in my study it took 10° to perform only a semicircle, a second shoot made a circle.

Hibbertia dentata (Dilleniaceæ), placed in the hothouse, moved with followed the sun & made (May 18th) a circle in 7° 20'; next day on the 19th, reversed its course & moved against the sun & made a circle in 7°. On the 20th moved against the sun one-third of a circle & then stood still.

On the 26th, followed the sun for two-thirds of a circle & then returned, to its the same starting point, taking for this double course 11° 46'.—

(38

Sollya Drummondii (Pittosporaceæ) moves against the sun; kept in greenhouse.

April 4' — 5 — 6 7

1s circle 4° 25' 2d do 8° — very cold day 3d do 6° 25' 4th do 7°. 5'

Polygonum dumetorum (Polygonaceæ) this case is taken from Dutrochet (p. 299), as I observed no allied plant: moves follows the sun; star three shoots cut off & placed in water, made circles in 3° 10', 5° 20' and 7° 15'.—

Wistaria chinensis (Leguminosæ), in greenhouse— moves against the sun.

May 13th — — 16

1' circle 3° 5' 2d [circle] 3° 20' 3d [circle] 2° 5'

May 24th — 25 [do] [do]

4th circle 3° 21' 5' do 2° 37' 6' do 2°35'

 

Phaseolus vulgaris (Leguminosæ), in greenhouse, moves against the sun.

May 1s circle 2° 0'

— 2d circle 1° 55'

3d — 1. 55'

Dipladenia urophylla (Apocynaceæ) moves against the sun.

April 18th 1' circle 8°

— 19th 2d [circle] 9° 15'

— 30' 3d [circle] 9° 40' (a)

[38v]

Dipladenia crassinoda, moves against sun

May 16 1' circle 9° 5'

July 20 2d [circle] 8°

— 21 3d [circle] 8° 5'

(39

Ceropegia Gardnerii (Asclepiadaceæ) moves against the sun.

Shoot very young, two inches in length: 1st circle was performed in 7° 55'

shoot still young — 2d circle 7°

long shoot — 3rd circle 6° 33'

do — — 4th 5° 15'

do — — 5th 6° 45'

Stephanotis floribunda (Asclepiadaceæ) moves against the sun & made a circle in 6° 40': a second circle in about 9°.

Hoya carnosa (Asclepiadaceæ) made several circles, in from 16° to 22° or 24°.—

Convolvulus major (Convolvulaceæ) moves against the sun.— Plant placed in room with lateral light

First circle 2° 42' {semicircle from light 1° 14' to light 1° 28' difference 14'

Second circle 2° 47' {semicircle from light 1° 17' to light 1° 30' difference 13'.

Convolvulus — ? perennial hardy sp. with large white flower),sepium (large-flowered cultivated var.) moves against the sun. Two circles, each in 1° 42'— difference in semicircle from & to the light, 14'

Ipomœa jucunda (Convolvulaceæ) moves against the sun, placed in my study, with windows facing the north-east; weather hot.

First circle 5° 30'. {semicircle from the light in 4° 30'; to the light 1° 0' difference 3° 30'

Second circle 5° 20', late in the afternoon: circle completed at 6° 40' P.m {semicircle from light in 3° 50' to light 1° 30' difference 2° 20'

(We have here a remarkable instance of the power of light in arresting retarding & hastening the revolving movement.) (a) see Back

[39v]

(a) Rivea tiliæfolia (Convolvulaceæ), moves against the sun & four revolutions in 9°; so that each on average was performed in 2° 15'.—

(40

Plumbago rosea (Plumbaginaceæ) follows the sun. The shoot did not begin to revolve until nearly a yard in height; it then made a fine circle in 10° 45'. During the next few days continued to move but irregularly. On Aug 15th the shoot made a followed during a period of 10° 40' a long & deeply zigzag course, apparently repeating two ellipses & and then made a broad ellipse. The figure thus traced altogether apparently represented three ellipses, each of which on averaged took 3° 33' for its completion.

Jasminum pauciflorum, Bentham (Jasminaceæ), moves against the sun. —First circle in 7 °15' —second rather more quickly.

Clerodendrum Thomsonii (Verbenaceæ) follows the sun.

April 12th 1st circle 5° 45' shoot very young

14 2d do 3° 30'

18 semicircle 5° 0' {directly after the plant was shaken in being moved

19 3d circle 3° 0

20 4th circle 4° 20'

Tecoma jasminoides (Bignoniaceæ) moves against the sun.

March 17th 1st circle 6° 30'

—19 2d do 7°

— 22 3d do 8° 30' very cold day

— 24 4th do 6° 45'

[40 bis]

[First 4 lines already transcribed in previous page]

Thunbergia alata (Acanthaceæ) moves against sun.

April 1 14 1' circle 3° 20'

— 18 2d do 2° 50'

— 3d do 2° 55'

— 4 do 3° 55' (late in afternoon)

Adhadota cydonæfolia (Acanthaceæ) follows the sun. A young shoot made a semicircle in 24° an older shoot made circle in 26° 30'. Subsequently made a circle in between 40° & 48°: subsequently did not complete a circle in 50°.— Another shoot, however, made a circle in 26°. 30'.— 

(41

Mikania scandens (Compositæ) moves against the sun.

March 14' 1s circle 3° 10'

— 15 2d do 3°

— 16 3d do 3°

17 4' do 3° 33'

April 7' 5' do 2° 50

— 6' do 2° 40' This circle was made after a copious watering with intentionally cold water at 47° Fahr.—

Loasa aurantiaca (Loasaceæ). First plants, moved against the sun.

June 20 1' circle 2° 37'

— 2d [circle] 2° 13'

— 3d [circle] 4°.

Jun 21' 4th circle 2° 35'

— 22' 5th [circle] 3° 26

— 23 6th 3° 5.

Second plant, followed the sun

July 11th 1' circle 1° 51'

2' — 1° 46'

3' — 1° 41'

4' — 1° 48'} very hot day

July 12th 5' 2° 35' cool morning

Scyphanthus elegans (Loasaceæ) follows the sun.

Jun 13' 1s circle 1° 45'

2' — 1° 17'

— 14th 3d — 1° 36'

— 4' — 1° 59'

— 5' — 2° 3'.

(42

Siphomeris or Lecontea (unnamed sp.) (Cinchonaceæ), follows the sun.

May 25th semicircle 10° 27  shoot extremely young

— 26 2d circle 10° 15 —shoot still young

30 2d circle 8° 55'

June 2d 3d [circle] 8° 11'

— 6 4th [circle] 6° 8'

— 8 5th [circle] 7° 20' {during night, taken from the hothouse & placed in the house a room in my house.—

(a)

Lonicera brachypoda (Caprifoliaceæ) follows the sun: in a warm room in the house.

April 14th 1' circle about 9° 10'

2d circle about 12° 20', shoot very young

3' [circle] 7° 30'

4' [circle] 8° 0'. In cir this latter circle, the semicircle from the light took 5° 23', & to the light 2° 37'; difference 2° 46'.—

Aristolochia gigas (Aristolochiaceæ) moves against the sun.

July 22d 1' circle 8° rather young shoot

23 2d [circle] 7° 15'

24 3d in about 5°

[42v]

(a) Manettia bicolor (Cinchonaceæ), very young plant, follows the sun.

July 7th 1s circle 6° 18'

— 8 2d do 6° 53'

— 9 3d do 6° 30'

(43

In the foregoing table, which includes twining plants, belonging to as widely different orders as is possible, we see that the contraction or turgescence of the cells circulating round the axis, on which the revolving movement depends, differs much in rate. As long as a plant remains under the same conditions, the rate is often remarkably uniform, as we see with the Hop, Mikania, Phaseolus &c. (a) A shoot of the Akebia quinata made one a revolution in 1° 30', & three revolutions at the average rate of 1° 38': & this is the quickest revolution observed; the hop Hop revolved in a reversed direction during hot weather at the average rate of 2° 8': a Convolvulus made two revolutions at the rate average of 1° 42' & Phaseolus vulgaris three at the rate average of 1° 57'.

On the other hand, some plants take 24° for a single revolution, & the Adhadota sometimes required 48°; yet this latter plant is an efficient twiner. Species of the same genus may move at any different rates. The rate does not seem governed by the thickness of the shoots internodes: shoots: those of the Sollya are as thin & flexible as string, but move more slowly than the thick & fleshy shoots of the Ruscus, which seems seem so little fitted for movement of

[43v]

(a) The Scyphanthus made one revolution in 1° 17' & this is the quickest rate observed; but we shall afterwards see a tendril-bearing Passiflora revolving even more rapidly.

(44

any kind: the shoots of the Wistaria, which become woody, move faster than those succulent shoot of the Ipomœa Thu or Thunbergia.)

(We know that the internodes, whilst still very young, do not acquire move at their proper rate acquire their proper rate of movement; hence the several shoots on the same plant will may sometimes be seen revolving at different rates. The two or three, or even sometimes more, internodes which are first formed above the cotyledons, or from a above the perennial root-stock, are upright & do not move; these shoots can support themselves from this small height, & nothing superfluous is granted.)

A greater number of twiners, as is well known, ascend from left to right, than is on opposite direction revolve in a course opposed to that of the sun, or to the hands of a watch, than in the opposite reversed course; & consequently, the majority, as is well known, move ascend their supports from left to right. In the same order Occasionally, though rarely, plants of the same order twine in opposite directions, of which Mohl (s. 125) gives a case in the Leguminosæ, & we have in the Table another a case in the Acanthaceæ.—

(45

(At present no instance is known of two species of the same genus twining in opposite directions; & this is a singular fact, because

same species viz of

different individuals of Solanum dulcamara (Dutrochet Tom. 19 p 299) revolve & twine in both directions. This plant, however, is a most feeble twiner; & therefore Loasa aurantiaca (Léon p 351) offers a much more striking case. I raised 17 plants: of these eight revolved in opposition to the sun & have ascended from left to right; five followed the sun & ascend from right to left; and from se revolved & twisted in one direction & these reversed their course*(B); (a) text The best example

Of these these latter one four plants, one made seven spiral [illeg] turns from right to left, & five turns from left to right. These case is individuals of the Loasa are interesting as showing how almost every change is effected most gradually. For another plant in the same Family. the Scyphanthus elegans habitually twines in this manner: I raised many plants, & the stems of all took one turn, or nearly two turns, in occasionally two or even three turns in one direction & then ascending from a short space straight, & reversed its their course &

[45v]

* I raised nine plants of the hybrid Loasa Herbertii, and six of these reversed their spire in ascending their supports.—

[45vv]

(a) (text)

; the petioles of the opposite leaves, affording a point d' appui for the end of reversal of the spire.

(41

[noted added in another hand:] 46A (2) Follows * on p. 46B

Twining plants

*The Solanum dulcamara, as we shall presently see, can only climb only support which only twine round such stems as are both thin & flexible. Most twining plants are apparently adapted to supports of different thicknesses. Our English twiners plants, as far as I have seen, never twine round trees, excepting the common Honeysuckle (Lonicera periclymenum), which I have seen observed twining round a young beech-tree nearly 4 1/2 inches in diameter. Mohl (s. 134) found kidney beans & that the Phaseolus multiflorus & Ipomœa Jucunda purpurea could not twine round sticks between three & four inches in diameter, when placed in a room with the light entering laterally; which fact was case understood as for thisinterfered in a manner presently to be explained with the revolving movement; but when in the open air, however, the Phaseolus twined round a support of the this thickness, but failed round one nine inches in diameter. Nevertheless some twiners, however, of the warmer temperate regions can manage this latter degree of thickness; for I hear from Dr. Hooker that at Kew the Ruscus androgynus ascends a column nine inches

(41 A bis

[Note added in another hand:] 46 A (3)

(Twining plants)

in diameter; & although my plants in a pot of the Wistaria in a pot tried in vain for weeks to get round a post between five & six inches in diameter thickness, yet at Kew a large plant ascended a trunk above six inches in thickness diameter. The tropical twiners, on the other hand, can ascend thick trees: I hear from Drs. Thomson & Hooker that this is the case with the Butea parviflora, (one of the Menispermaceæ), & with some Dalbergias & other Leguminosæ. This power would evidently be almost necessary for a Twining plant inhabiting a tropical forest; otherwise it could hardly ever reach the light. would have the line in dark shade:

In our temperate countries, any annual twining plants or are those which annually die down every year to the root, would probably suffer if they were not prevented from twining twined were enabled to twine round the trunks of trees, for they could not grow tall enough in a single season to reach the

(41 bis (B)

[Note added in another hand:] 46 A (4)

(Twining plants)

summit & gain to light.

(By what means certain twining plants are adapted to ascend only thin supports alone stems, whilst others can twine round thick trees, is not positively known. It appeared to me probable that twining plants with very long revolving shoots would be able to ascend thick supports; accordingly I placed Ceropegia Gardnerii near a post, six inches in diameter, but the very near its shoots entirely failed to get wind round it; their length & power of movement apparently aid some merely to in finding some distant, but thin stem round which to twine. We can, however, see, in accordance with the views previously explained, that a revolving shoot, which quickly lost its power of movement, after coming into contact with any broad support, would not again be drawn away form it by the returning

(41c bis

[Note added in another hand:] 46 A (5)

Twining plants

or opposite movement, & would thus remain in contact with the support, however thick, & would ascent it. But whether this slight slight difference in retaining for some time or in quickly losing the revolving power of movement after coming into contact with a support, alone determines the thickness how thick an support object the plant can ascend, I do not at know; not whether how far to a show the rate of revolution favours aids in determining the quicker or slower loss of the revolving power of movement the in shoots when arrested by some object.)

(46

took one or two turns in an opposite direction. The reversal of the curvature occurred at any point in the stem, even in the middle of an internode. Had I not seen this case, I should have thought its occurrence most improbable. It could hardly occur with any plant which twisted above a few feet in height or which lived in an exposed situation; for the stem could be easily pulled from its support with with every little unwinding to which it always only; nor could it have adhered at all, had not the internodes soon become moderately rigid. With leaf-climbers, as we shall soon see, analogous cases occur; but these present no difficulty,) as the stem is secured by the clasping petioles.)

(In the many other revolving & twining plants observed by me, I never but twice saw the movement reversed; once, & only for a short space, in Ipomœa jucunda; but habitually frequently with Hibbertia dentata.

This plant at first much perplexed me, for I continually observed its long & flexible shoots, evidently well fitted for

(46 bis A (1)

twining, make a whole or half or quarter a circle in one direction & then in the another. whe opposite direction. Consequently, when I tied the shoots to thin or thick sticks, or to var stretched string, it they seemed perpetually to be trying to ascend these these supports, but always failed. I then surrounded the plant with a mass of branched twigs; then with the shoots ascended & passed through them, but the shoot several came out laterally & depended their depending their extremities did not turn upwards as is usual with twining plants.

Finally I surrounded this another plant with many thin upright sticks, & placed it near the other with the twigs, & now Hibbertia had got what it liked, for it twined up the parallel sticks, sometimes winding round one & sometimes round several; & occasionally rare the shoots from one plant travelled laterally to the support round from one to the other plant.

(a) It seems clear would appear that this Hibbertia is adapted to

[46v]

(a) Though the revolving movement was sometimes in one direction & sometimes in the other; the twining was always invariably from left to right, so that the more potent or persistent movement of revolution is must be in opposition to the course of the sun.—

(46 bis (B)

twine occasionally to ascend by twining & then & to ramble laterally in the midst of the over & in the midst of the thick Australian scrub.)

I have described this case in some detail; because, as far as I have seen, it is most rare to find with twining plants any 'especial adaptations, in which respect they differ much from the more highly organised tendril-bearers.* Besides this case of the Hibbertia, the Solanum dulcamara, as we shall see, apparently can climb only thin & flexible supports. I suspect that those Tropical Twiners, of in which several long internodes slowly revolve together, have the power of twining round much thicker supports trunks than our the common twiners of temperate regions, which as we have seen are baffled by even a moderate thickness.)

(As Ferns differ so essentially much from phanerogamic phanerogamic plants, it may be worth while here to show how that the Twining species

(46 quat[illeg] C

From act in every in no respect in the same manner differently from other twining plants. In Lygodium articulatum, the two internodes first-formed internodes above the root-stock do not revolve move; the third from the ground revolved & at first very slowly. This species is a slow revolver: but L. scandens made five revolutions at an average rate of 5° 45'; per revolution for each & this represents fairly well the usual rate, in place taking quick & slower movers, amongst phanerogamic plants. The two uppermost internodes alone move. & The rate was accelerated by an increased temperature. The two young upper internodes alone moved. A line painted along the convex surface of the a revolving internode became first lateral, then concave, & ultimately convex again. Neither the internodes nor petioles are not affected by contact or rubbing. The movement is in the more more usual direction, namely, in opposition to the course of the sun; & when the stem has twined round a thin stick, the it is generally becomes twisted on its own axis in the same

(46D

direction. By the growth of the After the stem has internodes have twined round a stick, their continued growth of the internodes causes any each point them to slip a little upwards & onwards. If the stick be soon removed, the internodes straightens itself themselves & recommence revolving.

The extremities of a the the depending shoots turn upwards, & twine on themselves.

In all these respects we have complete identity with phanerogamic twining plants; & the above enumeration may serve as a summary of the chief points leading characteristics of common Twining plants.)

(The power of revolving depends on the general health & vigour of the plant, as has been laboriously shown by Palm. But the movements of the each separate internode as is so independent of each the others, that cutting off the an upper one did not affect the revolutions of the a lower one. When, however, Dutrochet cut off two whole shoots of the Hop & placed them in water, the movement was greatly retarded; for one revolved in 20° & the other in 23°, whereas

[46D]

[First 5 lines already transcribed in the previous page]

they ought to have revolved in between 2° and 2° 30'. Shoots of the Kidney-bean were similarly but retarded but in a less degree.

I have repeatedly observed that carrying a plant from the greenhouse to my house, or even

(47

from one part to another of the greenhouse to another part, always stopped the revolving movement for some a time; hence I conclude that during windy weather twining plants plants natural growing would not during very windy stormy weather make their revolutions. A decrease in temperature was always caused a considerable retardation in the rate of revolution; but Dutrochet (Tom. 17 p. 994, 996) has given such good precise observations on this head with respect to the tendril-bearing pea, that I need say nothing more. on this head. When twining plants are placed near a window in a room, with the light illuminated as usual by the light in some cases has a remarkable power (as was likewise observed by Dutrochet, p. 998, with the pea) on the revolving movement, but different in degree in with different plants; thus Ipomœa jucunda (as may be seen in the table), revolved in 5° 20'— the semicircle from the light taking 4° 30' & that towards the light only 1°:- Lonicera brachypoda revolved, in a reversed direction to the Ipomœa, in 8°,— the semicircle from the light taking 5° 23' & that to the light only 2° 37'. Judging from the rate of revolution during the night, [illeg] of similar being nearly to the same during the day almost I presume believe that the action of the light

[48A]

curious cases.* with most twining plants, all the branches, g when many are however many maybe produced, go on revolving together; but according to Mohl (s. 4) the the branches above & not the main stem of Tamus elephantipes, does not twine, only the branches. On the other hand, with a the climber Asparagus noti given in the Table, the leading shoot alone & not the branches, revolved &c twi twined; but I must add that the plant was not growing vigorously. With Periploca græca

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(a) does not greatly modify the rate of the complete revolution, but accelerate one semicircle & retards the other. This action of the light is remarkable when we reflect how little the leaves are developed on the young & very thin revolving internodes. & how thin these latter are. It is all the more remarkable as botanists have thought (Mohl, s. 119) that twining plants are exten but little sensitive to the action of light.)

I will conclude my account of Twining plants by collecting from the works of two four authors above before repeatedly quoted a few miscellaneous & curious cases.* The main stems of Tamus elephantipes, according to according to (Mohl, (s. 4) does not twine, but only the main branches:* in the with Periploca græca (Palm, s. 43) only the uppermost shoots & not the whole stem twine: in with Polygonum convolvulus there shoot is twining only during the middle of summer (Palm s. 43), 94); vigorously growing plants during plants growing vigorously in the autumn, plants growing even more vigorously then during the summer, show no inclination to twine.

The following cases are interesting, as being "analogous variation"; — due probably to reversions;— that

[48v]

(a) (text)

From the rate of revolution being nearly the same during the night & the day, I infer that the action of the light is confined to retarding one semicircle & accelerating the other, so as not to greatly modify the whole rate. of the whole circle.

(49

is a character the occasional appearance of is a character common to most of the species of the a group, occasionally appears, probably from reversion in a species cut [illeg] habitually thus [illeg]. Thus very many of the

The majority of Asclepiadaceæ are twiners; but Asclepias nigra only "in fertiliori solo incipit scandere subvolubili caule" (Willdenow, quoted & confirmed by Palm, s. 41): Asclepias vincetoxicum does not regularly twine, but has an upright stem, but occasionally (Palm, s. 42; Mohl, s. 112) when growing in moist shady or in very warm places under certain conditions.(a) Most species of Convulvulus are excellent twiners, but the shoot of C. batatas (Léon p. 681) are ordinarily short & little flexible "habituellement rarement volibiles." Most of the species of Phaseolus are twiners; but certain varieties of the P. multiflorus have produce (Léon, p. 681) two kinds of shoots, some upright & thick, & others thin & twining. I have seen striking instances of this curious case of variability in "Fulmer's dwarf Forcing Bean," with on which occasionally a long twining shoot appeared.)

(Solanum dulcamara is one of the feeblest &

[49v]

(a) (text)

So it is with two species of Ceropegia, as I hear from Prof. Harvey; for these plants in their native dry S. African home generally grow erect from six inches to two feet in height, very a very few taller specimens showing no some inclination to twine curve; but when cultivated near Dublin, they regularly twined up sticks five or six feet in height. Most Convolvulaceæ are excellent twiners; but Ipomœa argyræoides in S. Africa, as I have from the same authority almost always grows erect & compact & about twelve to eighteen inches in height; one specimen alone in Prof. Harvey's collection showing an evident disposition to twine; whilst seedlings raised near Dublin twined up sticks above eight feet in height. These facts seem the more height are highly remarkable; for there can hardly be a doubt that in the dryer parts provinces of S. Africa these plants have propagated themselves for thousands of generations in an erect condition; & yet during the whole time period have retained the power of spontaneously revolving & twining, when their shoots become elongated under proper conditions of life.

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poorest of twiners: it may often be seen growing as an upright bush, & when growing in the midst among [3 words illeg]of a thicket it merely scrambles up these merely scrambles up the branches without twining; but, even when according to growing near a soft & flexible support stem (Dutrochet (Tom 19 p. 299) it (a) will twine round it. We have probably seen the commencing cas stage of this habit. On the other hand, I suspect that with Tecoma radicans, we have feeble vestiges og a lost the a lost habit: this plant plant species plant belongs to a group abounding with twining & the allied with tendril-bearing plant, but it now ascends by rootlets like those of the ivy [illeg]; yet I observed that the growing internodes seldom remained quite stationary, but performed slight irregular movements ap apparently vestiges of the regular revolving movements of true twining plants. which could hardly be accounted for by changes in the action of light.— Nor let it Anyhow it need not be supposed that there would be any difficulty in the passage [text taped over] a regular twining especially Twining plant to a simple root-climber;

display

(a) for theyoung internode of BignoniaTweedyana & of Hoya carnosa revolve & twine, but likewise emit rootlets which adhere to any fitting surface.)

[50v]

family of Solaneæ, which are described as Twining plant, seemed to possess this faculty in a very flexible manner.—

[50v]

(a) grows near a thin & flexible support, such as the stem of a nettle, it twines up round it. I placed sticks round several plants, & vertical stretched strings close to others, & the strings alone were ascended by twining.

We here, perhaps, see the first stage in the habit of twining; & the stem sometimes ascends twines indifferently to the right & sometimes to or to the left. Some other species of the genus, & some other genera another genus, viz Habrothamnus of the same

(51

(Leaf-climbers.)

(It has long been well known that several plants climb by the aid of the foot-stalk of their leaves, either by the foot-stalks petioles or by their produced midrib; but beyond this, they have been little observed. Palm & Mohl class these plants with those which bear tendrils; but as a leaf is generally a defined object, the present classification has, at least, some plain advantages.— (a) I will begin with the genus Clematis.—

Clematis glandulosa. — The thin, long growing upper internodes of this Tropical species revolved, moving against the course of the sun, precisely like those of a true twiner, at an average rate, judging from three revolutions, of 3° 48'. — When a long thin stick was placed. The leading shoot immediately twined round a long thin stick, placed near it; but after making only made one and a half an open spire of only one & a half turns, it ascended for a short space straight, & then reversed its spire & wound wound two turns in an opposite direction. This course was rendered possible by the

[51v]

(a) There are other advantages, as leaf-climbers are intermediate in any many respects between Twiners & certain Tendril-bearing plants.

(a) Of with Clematis & Tropæolum I have observed eight species of Clematis & seven of Tropæolum in order to discern what amount of difference there might occur there may be within the same genus; — and the differences, as we shall see, are considerable.)

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(Leaf-climbers)

straight piece between the opposed spires having some become rigid. Whilst thus twining up a vertical stick, it made no use of its leaves. The simple, broad, ovate leaves of this tropical species, so unlike those of most of the other species of the genus, with thin short thick foot-stalks petioles, seem but ill-fitted for climbing any movement. Whilst twining up a vertical stick, no use is made of them. Nevertheless, if the foot-stalk of a young leaf be rubbed with a thin twig a few times on any side with a thin twig, it will in the course of a few hours bend to that side; afterwards it becomes straight again. The under side seemed to be the most sensitive; but the sensitiveness or irritability is slight compared to which that which we shall see meet with in some of the other following species; for a loop of string string, weighing 1.64 grain pla hanging for some days on a young footstalk, produced a scarcely perceptible effect. (a). A forked twig placed so as to press lightly on the under side of a young footstalk caused it to bend, in 12°, to bend greatly, & ultimately the leaf became to such an extent that the lamina leaf bent itself downward, upperside down, & passed to the opposite side

[52v]

A sketch is here given of two young leaves which had naturally caught twigs on each side of the stem. (Diagram I.)

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(Leaf-climbers)

of the a shoot stem: the forked stick being taken away having been removed, the leaf slowly recovered its former position.) (The young leaves change their position in a rather odd manner: when first developed the leaf-stalks petioles are upturned, parallel to the axis stem; they then bending down first at right angles to it;they then slowly bend downwards, remaining for a short time at right angles to the axis remaining for a short time at right angles to the stem & ultimately then become & becoming so much curved downwards arched downwards, that the tip lamina blade of the of the young leaf points to the ground,: they retain this position for some time, then bending with the its tip curled inwards; so that the whole petiole & leaf together form a hook. they

If they come into contact with no object, they retain this position for a considerable time, & then rise bending upwards, so that they foot-stalks reassume partially assume reassume in became upturned, thus is part assuming their primordial their original upturned position which they is retained ever afterwards. The hook-like formed shaped of The young leaf apparently serves leaves being hooked are thus enabled to catch twigs any twigs, with which it may be when brought into contact with them, by during the revolving movement of the growing internodes.— The petioles which have clasped any object in the course shortly soon became much thickened & straightened,) as may be seen in the diagram.)

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(Leaf-climbers)

Clematis montana. — The long, thin petioles foot-stalks of the leaves are long & thin, whilst young, are sensitive, & when not lightly rubbed bend to the rubbed side, subsequently becoming straight. They are far more sensitive than the foot-stalks petioles of C. glandulosa, for a loop of thread, weighing only a quarter of a grain caused them to bend; held a loop weighing half an inch only 1/8th of a grain sometimes acted & sometimes did not act. The sensitiveness extends close up to the angle between two stems & leaf-stalk. I may here state that I ascertained the weights of the string & thread used by in all cases by carefully weighing 50 inches of string & of thread in a chemical balance, & then by cutting I cutting off measured portions lengths.*a The main foot-stalk petiole carries three leaflets; each having a short, but separate petiole; there were but their short petioles are of the leaflets are not sensitive. A young inclined shoot (the plant being in the greenhouse) revolved one day made a large circle opposed to the course of the sun in 4° 20', but the next day which was being very cold, the revolution took time was 5° 10'.

A stick being placed near, the revolving stem the young petiole a leaf-stalk standing out at was soon struck by one of the petioles which stand out at right angles, were were soon brought into contact with it; & the revolving movement was thus arrested. The fo leaf-stalk petioles then

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*a One English grain equals nearly 65 milligrammes.

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(Leaf-climbers)

f, began, being excited by from the contact, to slowly wind round the stick.

When the stick was thin, it would they the petiole sometimes wind wound twice round it. The opposite leaf was in no way affected. The attitude thus assumed by the plant stem was like that of a man standing by a column, who throws his arm horizontally round it. With respect to the stem's power of twining, some remarks will be made under C. calycina.) (a) Clematis Sieboldi, resembles so closely in its habits the C. rosea present species, that nothing need be said about it.—

Clematis calycina. — The young shoots are thin & flexible: & in one revolved, describing a broad oval, in 5° 30' & another in 6° 12': they followed the course of the sun; but the course would certainly in this & therefore travelled moved in an opposite direction to that of the foregoing species; but the course in this & the other species but in all the species of this genus would the course followed no doubt be certainly have been found to vary, if they had been, if observed long enough would, no doubt would be found to vary. This is a

[55v]

(a) (Clematis Sieboldi. — A shoot made three revolutions against the sun at an average rate of 3° 11'. The power of twining is like that of the last species. Its leaves are nearly similar, except that the petioles of the lateral & terminal leaflets are sensitive. A loop of thread, weighing only 1/8th of a grain acted on the main petiole, but it took between two & three whole days to produce any effect.—)

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(Leaf-climbers)

rather better twiner than the other species: when a thin root upright stick free from twigs, was given placed near, the stem; this stem sometimes made two spiral turns round it; then being arrested by the clasping of the leaf-stalks, it would run up for a space straight, & then generally reversed its course & took one or two spiral turns in an opposite direction. This reversal of the spire occurred in all all the two three foregoing species.

The leaves are so small compared with those of most of the other species, that the leaf-stalks at at first seem seemed at first ill-adapted for clasping; but it was evident that soon became nevertheless, the main service of the revolving movement was is to entangle bring them into contact bring them with surrounding objects, which are slowly but securely seized. some leaf-stalks into contact with any support which was well but slowly clasped by them. The young leaves leaf-stalks, which alone are sensitive, have their further ends ends extremity bowed a little downwards, so as to be in a slight degree hooked; ultimately they the whole leaf leaves become flat. I gently rubbed with a thin twig the lower surfaces of the terminal petioles of the foot-stalk of two young leaves; surfaces, near the end extremity of two young leaf-stalks; &

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(Leaf-climbers)

in 2° 30' they were slightly curved downwards; & in 5° after being rubbed the end of the foot-stalk was bent completely back, parallel to the basal portion; & in in 4° subsequently the foot-stalk had secured & again it had become nearly straight again. To show how sensitive the young foot-stalks petioles are, I may mention that I touched, in order put a dot of to in order to mark them mark [illeg] with thin short strokes of thin water-colour, on their under side; of two foot-stalks, & this prod formed an infinitely thin crust, but was thus formed, but it sufficed in which when dry formed an excessively thin and minute crust; but this sufficed in 24° to cause both the foot-stalks to to bend downwards. Whilst the plant is young each leaf consists of three divided cut divided leaflets, which have barely distinct petioles, & these are not then sensitive; but when the plant is well grown, the two lateral & terminal leaflets have long petioles, & these have become quite are now become sensitive, & are capable of clasping in any direction any object.

(When a foot-stalk petiole has clasped any object an a twig, it undergoes some remarkable changes, thus which occur with the several other species, but in a less strongly

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(Leaf-climbers)

marked manner, & will here be described once for all. The foot-stalk swells greatly clasped petiole in the course of two or three days swells greatly, & ultimately becomes nearly twice as thick as the convex opposite leaf-stalk which has not clasped nothing anything. When thin transverse slices slices of the two are placed under the microscope, their difference is conspicuous: the side of the foot-stalk, which has been in contact with the support, has is now formed of a layer of colourless cells, with their longer axes directed from the centre of the foot-stalk petiole, & very much larger than the cells formed in the opposite opposite or unchanged foot-stalk petiole; & the central cells was also, are in some degree enlarged, & the whole is much indurated. The exterior surface of the foot-stalk is generally coloured bright red. & the whole foot-stalk often twisted. But a far greater in change has taken place in the nature of the tissues has taken place there can be than that which can be seen, the foot-stalk is externally visible; the petiole of the unclasped leaf is flexible, yet & can be easily snapped brittle & can be easily snapped, whereas the clasped one acquires an extraordinary

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(Leaf-climbers)

toughness & rigidity, & can hardly be broken, so that considerable force is required to break pull it into pieces.

With this change, great durability is probably acquired; at least this is the case with the clasped leaf-stalks of Clematis petioles of Clematis vitalba. The meaning of these specialised changes of structure in the clasped leaf-stalks is plain, namely that they the leaf-stalks petioles may efficiently firmly & durably support the stem.)

Clematis microphylla, var. leptophylla. — A plant received from Mr. Veitch under this name is I presume a variety of the Australian C. Microphylla. The long & thin internodes of this Australian species revolve, sometimes in one direction & sometimes in an opposite one, making describing long, narrow, irregular ellipses or large circles; four revolutions were completed at nearly (at a within five minutes) of the same average rate of 1° 51': so that this species moves more quickly than the others of the genus. The shoots when placed

(59A

(Leaf-climbers)

near a a vertical stick either twined round them it, or clasped them it with the basal part portions of their petioles. The leaves are nearly of the same general shape & act as like a hook, whilst young in the same manner whilst young, as described in under the following species; & will presently be described but the leaflets are m more divided, as in C. calycina, & each segment, bears whilst young terminates in a hardish hardish point & is much curved downwards & inwards; so that the whole leaf easily becomes entangled readily catches & becomes entangled with any neighbouring object. The petioles of the young terminal leaflets are acted on, whilst young by loops of thread weighing only 1/8th & 1/16th of a grain: the basal portion of the main petiole is much less sensitive, but will clasp a stick against which it presses.) (The whole leaf, whilst young

(59B

(Leaf-climbers)

& hooked is in continual & spontaneous, slow movement. The stem was secured close to the base of the leaves, & a bell-glass placed over a shoot, & the movements of the leaves were traced during several days. A very irregular line was generally formed; but one day in the course of 8° 45' eight hours & three quarters, the figure traced clearly represented three & a half irregular ellipses; the most perfect one of which was completed in 2° 35'. The Three The two opposite leaves moved quite independently of each other. This movement would aid that of the internodes in bringing the leaves petioles into contact with supporting surrounding objects to be clasped. I observed discovered this spontaneous movement too in the leaves of the present species too late to be enabled to observe the several other species; but from analogy I can hardly doubt that the leaves of at least of C. viticella,

(59C

(Leaf-climbers)

, flammula, & vitalba move spontaneously; whether those this is the case with C. montana, calycina calycina &c must remain doubtful: I ascertained that the simple leaves of C. glandulosa have exhibited no spontaneous revolving movement.

Clematis viticella (var. venosa). — In this & the two following species the power of spirally twining is completely lost; & this seems due to the thickness lessened flexibility of the internodes & the gen interference from the great caused by the large size of the leaves. yet But the revolving movement, though greatly lessened,restricted, is not lost. In our present species, the a young internode, placed in front of a window made three narrow ellipses, transversely to the light, in at an average rate of 2° 40': when placed so that the movement was to & from the light, the rate was greatly accelerated & retarded affected as with twiners as in the case of Twining plants. The ellipses were small; the longer diameter described by the apex of the a shoot bearing has a pair of not expanded leaves moved being only 4 5/8 from of an inch; & that by the apex of the penultimate internode only 1 1/8 of an

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(Leaf-climbers)

inch: under at the most favourable time period of growth, the each leaf would not probably hardly move even move be carried by the movement of that 2 or to & fro by the movement of the internodes more than two or three inches; (a)

Consequently the movements the movements of the whole shoot by the wind & the its rapid growth of the shoot would probably be equally or more effective efficient in bringing the leaves into contact with a support the surrounding object than the revolving motion.)

(The leaves are of large size, & whilst young & sensitive of a remarkable shape. There are three pairs of lateral leaflets & a terminal one, all borne by rather long petioles. The main medial foot-stalk petiole bends a little angularly downwards at each point when where a pair of leaflets moves arises, & that terminal foot-stalk the petiole of the terminal leaflet is [in margin:] (Diagram 2.) bent downwards at right angles; hence the whole foot-stalk form a in little downward bent curved downwards with a petiole, a with its rectangularly bent point extremity, & acts efficiently like as a hook. This hook, together together with the lateral petioles, directed a little upwards; altogether altogether forms an excellent grappling apparatus, by which the leaves may readily become entangled with surrounding objects with in the branches in any surrounding branches. If they catch nothing, the

[60v]

(a); but as recently stated it is probable that the leaves themselves more spontaneously. The movement of the whole shoot by the wind & by its rapid growth would probably be equally efficient with the several spontaneous movements in bringing the leaves petioles into contact with surrounding objects.)

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(Leaf-climbers)

f foot-stalks whole petiole ultimately grows straight & the whole leaf nearly flat. Both the medial & lateral foot-stalks petioles are all sensitive; & and the basi-lateral petioles leaflets often consist of foot-stalks pair are often generally subdivided into three branches, arranging stem & stem also which likewise are sensitive.

The basal portion of the main medial petiole foot-stalk between the stem & the first pair of leaflets is less sensitive sensitive than the other parts remainder; yet it will clasp a stick when in contact. On the other hand, the inferior surface of the rectangularly bent terminal portion (carrying the terminal leaflet), which forms the inner side of the end of the hook is the most sensitive part, & this end would is manifestly best adapted to catch a distant object support. For example To show the difference in sensibility, I gently placed loops of string of the same weight (in one instance weighing only .82 of a grain) on two other of the over the the lateral foot-stalk & on this so the terminal foot-stalk petiole; in a few hours the latter was bent, but after 24° no effect was produced on the any of the lateral foot-stalks petioles.

Again a terminal foot-stalk hooked on the placed in contact with a thin stick became sensibly sensibly curved in 45' & in 1° 10' had cur moved through ninety degrees; whereas the a

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(Leaf-climbers.)

lateral foot-stalk petiole did not become sensibly curved till until 3° 30' had elapsed. In this latter case & in all other such cases, when if the sticks was is are taken away, the foot-stalks petioles continued to move for during many hours afterwards; so they do after a slight rubbing; with a two twig; but ultimately, if the flexure has not been very great or long-continued, they foot-stalk become after about a day's interval, becomes straight again.

(The gradation in spreading of the gradation in the extent of extension of the sensitiveness in foot-stalks petioles of the (three) several already named species deserves notice. In C. montana it is confined to the main fo petiole & has not spread to the petioles of the three leaflets; so it is with young plants of C. calycina, but in older plants it spreads to the three petioles. In C. viticella it has spread to all seven the all seven the petioles of the seven leaflets, & the terminate sub-divisions of the basi-lateral leaflets petioles. In this alone the sensitiveness has diminished in the basal part of the main petiole, in which alone it resided in C. montana; & has accumulated