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in the hook-shaped terminal extremity abruptly bent terminal portion.

Clematis flammula. — The shoot shoots, which are rather thick, straight & stiff, whilst growing vigorously in the spring, make small oval revolutions, following the sun in their course. Four were made at an average rate of 3° 45'. The apex longer axis of the oval, described by the extreme tip, (a) was in one case was only 1 3/8, & in another case 1 6/8 of an inch; so that the young leaves are moved a very short distance. The shoots of the same plant observed in midsummer, when growing slowly not so quickly, did not revolve at all.—

Consequently this This species must cli mainly depend on its own growth ascertained, spontaneous movements of its own leaves, on the rapid growth of the shoots & the on movements from the wind, for clasping any object; hence perhaps (c) the great [illeg], as we shall see, of its leaf-stalks.—)

The leaves are end of the foot-stalk in petioles are bowed downwards, & have the same general hooked form as in C. viticella. The medial petiole & lateral petioles are sensitive, especially the much bent terminal portion. As the sensitiveness is here greater than in any other species of the genus observed by me, & is in itself remarkable, I will give fuller details. The leaf-stalks, when so young that they have not separated from each other, are not sensitive;

[63v]

(a) was directed at right angles to the line joining the opposite leaves; its length was

[63]

(B) I cut down another plant in the early summer, so that by August 1st it had formed new & moderately vigorous shoots; these when observed under a bell-glass on some days were stationary & on other days moved to & fro only about the eighth of an inch to & fro. Consequently the revolving power is much enfeebled & under unfavourable circumstances is nearly lost in this species, which it must chiefly depend on the probable though not

(c) it is, that the petioles have acquired in compensation their a higher degree, as we shall see, of sensitiveness.)

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: when the lamina of a leaf is quarter of an inch in length, that is about one-sixth of its full size, the sensitiveness is in, highest state the most perfect & fullest the highest;but at this period the petioles are much more fully developed proportionally to the leaves proportionally than are the laminæ of the leaves. Full-grown f petioles are not in the least sensitive. A thin stick placed so as to press lightly against a petiole, bearing a leaflet quarter of an inch in length, caused the petiole to bend in 3° 15'; in another case the a petiole curled curled completely round a stick in 12°. These petioles were left curled round the stick for 24° & the sticks were then removed; but they petioles never straightened themselves. I took a twig, thinner than the petiole itself, & I rubbed lightly rubbed with it some of so with it several petioles four times, up & down; these in 1° 45' was became slightly curved; the curvature increased during some hours & then began to decrease, but after 25° from the time of rubbing a vestige of the curvature could be detected remained. Some petioles similarly rubbed once up & down became perceptibly curved in about 2° 30'; a terminal petiole petiole moving more than the a lateral obj petiole; they all became quite straight again in between 12° & 14°.—

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Lastly, a length of about 1/8th of an inch of a petiole, similarly rubbed only once down with the same twig, became slightly curved in 3° & remained so for during 11° till night; but the next morning it was quite quite straight.)

(The following observations are more precise. After seeing heavier finding that heavier pieces of string & thread acted, I placed a loop of string, weighing 1.04 gr. on a terminal petiole: in 6° 40' a curvature could be seen; in 24° the petiole formed an open ring round the string; in 48° the ring had almost closed on the string, & in 72° it had firmly seized the fine twine, so that it required some force to withdraw it. A loop weighing 0.52 of a grain caused in 14° a lateral petiole to just perceptibly to curve in 14°, & after 24° it had moved through ninety degrees. These following observations were made during the summer: the following were made in the spring, when the petioles apparently are more sensitive: a loop of thread, weighing 1/8th of a grain produced no effect on the lateral petioles, but placed on a terminal one, caused in it, after 24° a moderate curvature; this though though which after 48° was diminished, the loop still remained suspended, was after 48°

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diminished, but never disappeared; showing that the petiole was had become in some degree partially accustomed to the insufficient stimulus. This was experiment was twice repeated with nearly the same result.

Lastly a loop of thread weighing only 1/16th of a grain (nearly equal to four milligrammes) was twice gently placed by by a forceps on a terminal petiole (the plant being of course in a still & closed room), & this weight certainly caused a flexure, which very slowly increased until the petiole had moved through nearly ninety degrees: beyond this it never did not move; nor did the petiole, the loop remaining suspended, ever become quite perfectly straight again.)

(These facts, When we consider the softness of the cotton thread & whole, on the one hand, the thickness & stiffness of the petioles; & on the other hand, the thinness & softness of fine cotton thread, & what an extremely small weight 1/16th of a grain, these facts are are become highly are remarkable.

But I have reason to believe that even a less weight would not, if causes curvature when if actin over a broader surface than can be affected by thin thread. can act. Having noticed that the tail

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of a f piece of string a suspended pieces of string, which accidentally had touched a petiole, had acted on it caused it to bend, I took two short pieces of shor thin string twine at (10 ten inches in length (weighing 1.64 gr) & tying them to a stick, let them hang as nearly vertically perpendicularly downwards as they would & quietly their thinness & flexuous nature nature after being stretched would permit; I then quietly placed their tip ends so as just to rest on two petioles, with their tips hanging projecting about the tenth of inch beneath; stem: & both these petioles certainly became curved in 36°. and in 48° One of these tips of a the ends of string string touched the angle between the a terminal & one of the lateral petioles was in 48° caught as in a [illeg]by a forceps between them. In these cases the pressure, though spread over a much wider surface than that touched by the cotton thread, must have been almost excessively slight.—

Clematis vitalba. — My plants in pots were not healthy, so that I dare not trust my observations, which indicated much similarity in habits with C. flammula to the last species. I mention this species only because I was saw many proofs that the leaf-stalks petioles of

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plants growing naturally are excited to movement by very slight pressure. For instance, I found leaf-stalks petioleswhich had clasped thin withered blades of a grass, the soft le young leaves of a maple, & the lateral fl flower-peduncles of the quaking grass or Briza,— The latter was seen are being only about as thick as the hair of a man's beard, but they were completely surrounded & clasped. The petioles of a leaf, so young that none of the leaflets had expanded, had partially clasp seized a tw twig. The petioles of all almost old every old leaf, even when unattached to any object, are much convoluted; but this is owing to their having come come, whilst young, into contact during several hours with a support, some object which had been lost either from movement subsequently removed either by the wind or by the plants' own growth. In the plants of the several With the several above-described species, cultivated in pots & thus carefully observed, there never was any bending movement curling of the petioles without the necessary excitement from the stimulus of contact.

When winter comes, the laminæ of the leaves winter comes on, the blades of the leaves of C. vitalba drop off; but the leaf-stalks petioles (as was observed by Mohl) s. remain, & sometimes for during two seasons, & being convoluted, they curiously resemble true

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tendrils, such as those occurring in the allied genus Naravelia. The leaf-stalks petioles which have clasped an object are much more woody, stiff, hard & polished than those which have failed in this obj their proper purpose.)

(Tropæolum — I observed T. tricolorum, azureum, pentaphyllum, peregrinum, elegans, tuberosum, elegans and a dwarf var. of, as I believe, of minus.)

(Tropæolum tricolorum, var. grandiflorum. — The point was unfortunately placed in the hot-house; it grew most vigorously, ran climbed up a tall stick, then became unhealthy & did not flower; but I can hardly suppose that the two great heat will have affected the habits of the plant whilst growing vigorously.

The flexible shoot, f which first appears rises from proceeding from the bulb tuber, is scarcely thicker than we the tuber the root stick is as thin as twine. & One revolved in a course opposed to the sun, at an average rate from three revolutions, of 1° 23'; but no doubt the direction of the revolving movement is wasvariable. When the plant had grown very tall & much branched, all the

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shoots were curled owing many lateral shoots continued to revolve. The stem, whilst young, twined prettily prettily very wellspirallyround a thin vertical stick, but when grown older being it often ran up straight for a space being arrested by the clasping petioles, & then twine made one or two spires in a reversed direction. Until the plant had grown to a considerable height of two or three feet, a month from the first shoot shoot appeared above the ground, no true leaves, are produced; but in their place little filaments coloured like the stem were produced. The extremities of these these filaments are pointed, (a) little flattened, & at the extremity, with slight ridge on one side, like the midrib of a leaf, with a slight corresponding hollow on the opposite side: in fact they are petioles, bearing a mere vestige of the laminæ; but this rudiment never became developed into a leaf. leaf itself. These filaments & likewise the petioles of the true leaves, whilst young are highly sensitive on all sides to a touch.

The slightest rub caused them to curve towards the touched rubbed side in about three minutes; one made a bent itself into a ring in six minutes; they subsequently become straight again: if, however, they have completely clasped a stick, when this be is removed, they do not

[70v]

(a) a little flattened & furrowed on the upper surface. They never become developed into leaves. But as the plant grows in height, the filaments which are produced have with slightly enlarged tips; & then they bear a rudimentary leaflet up the leaf segment on each side of the medial segment, & soon other segments are produced until a perfect leaves are produced is formed, with seven deep segments. So that on the same plant we see every step, from the tendril-like filaments to perfect leaves. Hence this plant might be classed with tendril-bearers.

These filaments, as well as the petioles of the perfect leaves, whilst

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recover themselves. But The most remarkable fact and one which I have observed in no other species of the genus, is that the filaments & the petioles of the young leaves, if they catch no object, after standing out motionless in their original position for some days, spontaneously & slowly move moved, oscillating a little from side to side towards the stem. & supporting stick. Hence all the petiole petioles & filaments though arising on all different sides of the axle axis, ultimately bend bent bend towards & clasped clasp either it or the supporting stick. The petioles & filaments often showed some tendency become in some become, after clasping an object become after a time in some degree degree spirally contracted. In these spontaneous spontaneous movements & in the abortion of the laminæ of the leaf, these clasping & sensitive filaments, presented present a much nearer approach to the condition of a true tendrils than in any other, with the exception of Corydalis claviculata, which indeed may be classed either as a leaf-climber or tendril-bearer.) true leaf- climber case observed by me;— I much wish I knew whether the unnatural heat of the hot-house had played any part in the production of these filaments.—

Tropæolum azureum. — th an upper internode made four revolutions, following the sun, at an average rate of 1° 47'. The stem twined spirally in the same irregular manner as in that of the last species: This species it

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produced no filament or rudim petioles destitute of laminæ or rudimentary leaves. The petioles of the young leaves are very sensitive; a single light rub with a twig causing caused one to move perceptibly in 5' & another in 6': the former became became bent at right angles to its original position in 15' & &: it became straight again in between 5° & 6°. A loop of thread weighing 1/8th of a grain, caused another petiole to become curved curve.

Tropæolum pentaphyllum pentaphyllum. — The species had lost plant observed by me had not the power of spirally twining, which seems caused by due not to a want of flexibility in the stem, but rather to the continual interference from the clasping petioles. An upper internode made three revolutions, following the sun, at an average rate of 1° 46'. (a) The petiole of the a young leaf after a slight rub became curved in 6'; on any side became curved; ; one became bent; another on a cold day & one in 20' but generally in from 8' to 10'; & the curvature in generally usually becomes have greatly considerable increased greatly in from 15' to 20'. The petioles become become straight in from generally in about from again in between 5° and to 6°;

[72v]

(a) The purpose of the revolving movement in these & all the species manifestly to bring the petioles into contact with some & some supporting object. —

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but under and on one occasion in 3°. When a petiole has fairly clasped a stick, it cannot, on the removal of the stick, recover itself; but the free upper part of a still clasped petiole, retains its sensitiveness which had already clasped a stick by its basal part still has the power of movement. A loop of thread weighing 1/8th of a grain certainly caused the petiole to curve; but the stimulus is was not sufficient, the loop remaining suspended, to cause a permanent flexure. If a much heavier loop is placed in the angle between the petiole & the stem, it produces no effect; whereas we have seen with the angle between the stem & lateral petiole of Clematis montana is is sensitive.

Tropæolum peregrinum. — In a young plant seven inches high, the two lower internodes did not revolve, showing another point of close similarity with the movements of Twining plant. The four upper internodes, now revolved made three revolutions irregular revolutions, in a course opposed to the sun, at an average rate of 1° 48'. It is singular how closely similar alike the average average rates (taken, however, but from few observations)

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has been in of this with and the two last with the present species species have been, namely 1° 47', 1° 46', and 1° 48'. The present species cannot spirally twine, which seems mainly due to the rigidity of the its stem. In a very young plant, which did not not revolve, the petioles were not sensitive. In older In older plants, the petioles of very young leaves & of leaves as much as an one inch and a quarter in diameter are sensitive. A slight moderate rub caused one to curve in 10', but others generally not they did not others in 20': the petioles became straight again in between 5° 45' to 8°. & Petioles which have naturally come into contact with a stick, will sometimes take two turns round it: The clasped petioles when clasped they become rigid & hard. The petioles are less sensitive to a weight than in the previous species, for loops loops of string weighing .82 grain of a grain did not cause any curvature, whereas whilst a loop of double this weight (1.64 gr) did act.

Tropæolum elegans. — I did not make many

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observations on this species. The short & stiff internodes revolve irregularly & describe extremely small oval: one was completed in 3°. A young petiole, when rubbed, became slightly curved in 17'; much more so & was nearly straight again in 8°.

Tropæolum tuberosum. — The shoot on a plant nine inches in high did not move; but when grown taller, they moved irregularly & made very small imperfect ovals. These movements could be detected only by placing a bell-glass over the plant, & tracing on the glass a coloured line: sometimes the shoot shoos stood still for hours; during some days they moved only in one direction in a crooked line; on other days they made small irregular spires or circles, one being m completed in about 4°. The movement of the apex from side to side extreme point to point was only of the oval was about one or one and a half inches. Yet this slight movement brought the petioles into contact with some closely surrounding twigs, which were then clasped. stick sticks with

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With the lessened power of spontaneously revolve revolving movement, the sensitiveness of the petioles is also diminished. These when rubbed four or five times, did not become curved until half an hour had elapsed; the curvature increased during the next two hours; & they very slowly became straight again; sometimes requiring 24° for this purpose.

It is remarkable The petioles of very young leaves act act perfectly more efficiently; well; one with the lamina of the leaf only .15 of an inch in diameter, that is about a was twentieth of the full size, came into firmly clasped a thin twig: leaves, however, one quarter of their of their full-grown size size can act.

Tropæolum minus? a variety named described as a p a prostrate "dwarf crimson nasturtium" had no power of revolving movement in its internodes: but these moved during the day to only to & from the light during the day & from it at night in a rather irregular course. The petioles when well rubbed, showed no curvature; nor could I see that they ever caught clasped any surr neighbouring object. We have seen in

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this genus a gradation from species such as T. tricolorum, which have extremely sensitive petioles & and the internodes of which have strongly pronounced rapid revolving powers & can irregularly spirally twine up a support, to other species such as T. elegans & tuberosum, the petioles of which have feeble revolving powers & cannot spirally twine round any a support, to this last species, which has entirely lost or never acquired these faculties.

But from From the general character of the genus, the loss of power seems the more probable alternative.)

(In the present species & in T. elegans & probably in many others, the flower-peduncle, as soon as the seed-capsule begins to swell, spontaneously bend abruptly downwards & becomes somewhat convoluted. When a stick lies in the path, it will is to a certain extent seized clasped; but, as far as I have been able to observe, this movement of the peduncle is independent of the stimulus from contact.)

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Antirrhineæ. — In this tribe (Lindley) of the Scrophulariaceæ, at least four of the seven included genera are have leaf-climbing species.

Maurandia Barclayana. — The A thin, slightly bowed shoot ma made two revolutions, following the sun, each in 3° 17': this same shoot on, the day before act was revolving revolved in an opposite direction. The shoots do not at spirally twine, but climb excellently by the aid of the young sensitive petioles. brought into contact

These petioles, when rubbed, move after a considerable interval of time, & subsequently recover themselves: a loop of thread weighing 1/8th of a grain caused them to bend.)

Maurandia semperflorens climbed in a similar manner.

Maurandia semperflorens. — This freely-growing species climbs exactly like the last, by the its sensitive petioles. The A young internode made two circles, each in 1° 46'; so it moves almost twice as rapidly much quicker than as the last; but I should not have noticed it, had it not been for the following

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as in fact unique case. Mohl says (s. 45) that "the flower-peduncles, as well as the leaf-st petioles are wound into tendrils;" & he adds nothing more about the species genus. But it must be observed that Mohl classes as tendrils even such objects as the spiral flower-stalks of the Vallisneria. Nevertheless this remark, & the well-known well-known fact that the flower-peduncles of Maurandia are become flexuous led me carefully to examine them. They never act as tendrils. I repeatedly placed thin sticks in contact with young & old peduncles, & I allowed nine vigorous plants to grow in the overan entangled mass of branches; but in no one instance did a peduncle bend round any object. It is indeed in the highest degree improbable that this should co occur, for the flower-peduncles are generally developed on the branches which have already long ago have securely clasped by their petioles a support; & when developed on free depending

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branches, they are not borne by the young internode which still retains the revolving power of revolution by which they might be brought into contact with some surrounding objects. Nevertheless, & this is the remarkable fact, these flower-peduncles, whilst young, exhibit a feeble revolving powers powers of revolving & are slightly sensitive to a touch.

Several twines I firmly tied to a stem, I selected some a stems one which had firmly clasped a stick by their petioles, & placing a bell-glass over it them, was traced the movements of the young flower-peduncles. Some days these moved in an over a short & extremely irregular course, making little loops in the line. One day two a young peduncle one inch & a half in length inches in extreme length was carefully observed & it made four & a half narrow, vertical, irregular, & very short ellipses, each at an average rate of about 2° 25': an second adjoining peduncle described under during the same time similar, but fewer, ellipses. As the plant had for some time occupied exactly the same position, these

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movements could not be attributed to the varying the action of the light. A peduncle bearing a bud in which Peduncles, old enough for the coloured petals to be just visible, exhibit do not movement move.

With respect to irritability, I rubbed a few times very lightly with a thin twig two young peduncles, (one & a half (1 1/2 inches in length), one on the upper side, the other on the lower side, & they became in between from 4° & 5° plainly bowed in opposite directions towards the rubbed sides; in 24° subsequently they straightened themselves. (a) Two other & other & younger & adjoining peduncles (3/4 of inch in length) were lightly rubbed on their adjoining sides & they became so much bowed towards each other, that the arcs of the bows stood at nearly 90° deg right angles to their previous position; this was the greatest movement seen by me: subsequently they straightened themselves. Other peduncles, so young, as to be only 3/10th of an inch in length became curved when rubbed. On the other hand, peduncles above 1 1/2 inch in length required to be rubbed two or three

[78Cv]

(a) Next day they were rubbed on the opposite sides & they became perceptibly curved in an opposite direction curved towards these sides.

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times & then become only just perceptibly curved. Loops of thread suspended on the peduncles produced no effect; loops of string (weighing .82 & 1.64 grains) so acted copiously sometimes causing a slight curvature; but they were never clasped, as were the far lighter loops of thread by the petioles.)

(In the nine vigorous plants which I observed, it is cer certain that neither the slight spontaneous movements nor the slight sensitiveness of the flower-peduncles are of a made of of any use service to the plants in climbing. If any member of the Scrophulariaceæ Order were had been known to have flower-peduncles, which were used for climbing or had tendrils produced by their modification, I should have thought that the Maurandia still retained a useless or rudimentary vestige of a former habit; but this view cannot be maintained. We are almost compelled to believe

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that by some correlation of growth at the same the power of movement has been transferred from the young internodes to the young peduncles." & in the same manner sensitiveness from the young petioles to the young peduncles; but this latter supposition is the more improbable, as I could detect no sensitiveness to contact in the young internodes of the Maurandia, though in a closely allied genus, Lophospermum, the young internodes, as we shall see, are sensitive.

By whatever means the peduncles of the Maurandia have acquired their power of spontaneous movement & sensitiveness, the case is very interesting for us; for we can see that by a little perfecting of thin now useless capacities, the flower-peduncles could be made as useful for climbing, as are the flower peduncles of the Vine & Cardiospermum, which will hereafter be described.)

Rhodochiton volubile. — A long flexible shoot swept a large circle, following the sun, in 5° 30'; but and, as the day became warmer, a second circle was made completed in 4° 10'. The shoots twice sometimes make a whole or half spiral spire round a vertical stick, then runs run up for a space straight, & then

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make a second spiral turn in an opposite direction. The petioles of very young leaves, about one-tenth of their full size, are highly sensitive, & bend towards the side which has been touched; but they but do not move quickly: one after being lightly rubbed was perceptibly curved in 1° 10'; & became considerably arched in 5° 40' after the rubbing: some other petioles, after being rubbed, were scarcely curved in 5° 30', but in 6° 30' were distinctly curved. A loop string, about 1 grain in weight caused movements in 5°. Movement commenced in A curvature was perceptible in a petiole in between 4° 30' and 5° after the suspension on a petiole of a little loop of string: sweeping about on grass. A loop of fine cotton thread, weighing only 1/16th of a grain not only caused a petiole slowly to curve bend, but was ultimately firmly clasped by it, so that it could be withdrawn only by some little force. (a))

Lophospermum scandens (var purpureum). — The a Some long, moderately thin internodes made four revolutions at an average rate of 3° 15'. The course pursued is was very irregular,— sometimes ellipses w an extremely narrow as the ellipse, sometimes a large

[79v]

(a) The petioles when coming into contact with a stick, take either a complete or half a turn round it, & small increase in size.

Leaves not stan arising on the side of the stem opposite to the light, move towards it, & in doing this the petioles are sometimes brought into come into contact with the stem, which sometimes excites them to bend round it; & consequently clasp it; but the petioles have no true spontaneous movement.)

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circle; sometimes are irregular spire or zig-zag line, & sometimes the apex stood still. The young petioles, when brought brought by the revolving movement into contact with a stick, clasped clasped it & soon swell much increase considerably in size; but they are not quite nearly so sensitive to a weight as those of the Rhodochiton, the a weight,for loops of thread weighing 1/8 of a grain, not aiding any curvature did not always cause them to bend.)

(This plant presents a case not not observed in any other leaf-climber or twiner or tendril tendril-bearer; namely that the young internodes itself themselves are sensitive to a touch. When a petiole an clasps a stick, it possess draws the base of the next superior young internode above it above against it; & then the internode itself bends towards the stick, so that which is then caught between the stem & the petiole as by forceps a pair of pincers. The internode straightens itself again, excepting the part in contact with the stick. Young internodes alone are sensitive, & all parts of these will curve when rubbed. I made fifteen trials on several interdone on all thin side; & in about from 2° but in one case in 3° all were bent; (a) One internode which was lightly rubbed in one case a curvature was

[80v]

(a); they became straight again in about 4° subsequently.

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perceptible in 1° 25' rather more rarely. Six or seven times with a twig, became just perceptibly curved in 1° 15'; & in 4' 3° subsequently the curvature became considerable; but & the stem became straight again in the course of the night. I rubbed same internodes one day on one side, & the next day either on the opposite side or at right angles; & the curvature was always towards the rubbed side.)

Possibly this sensitiveness of the axis may be a compensation of the lessened sensitiveness of the petioles, in comparison with those of the Rhodichiton & Maurandia.—

According to Palm (s. 63) the petioles of Linaria cirrhosa, & to a limited degree those of L. elatine have the power of clasping a support.)

Solanum jasminoides. — Some of the species in this large genus are twiners; but this next is a true leaf-climber. The long, nearly upright shoot revolved made four revolutions, moving against the sun, very regularly at an average rate of 3° 26'. The shoots, however, sometimes stood stand still.—

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It is considered a greenhouse plant; but when kept there, the petioles took several days to clasp a stick: in the hothouse a stick was clasped in 7°. In the greenhouse a petiole was not affected by a loop of string, suspended during several days & weighing 2.5 2 1/2 grains;

(Diagram 3] (a) In this specie plant leaf-climber plant, & in no other species leaf-climber seen by me, a leaf grown to its full-sized leaf was capable was capable of clasping; but the movement was so extraordinarily slow that in the greenhouse, the act required some two several weeks, so extraordinarily slow was the movement; but on each succeeding week, it was clear that the petiole had become more & more curved, until it finally clasped the stick.) (When the flexible petiole of a half- or quarter-grown leaf has clasped any object, in three or four days it swells increases much in thickness, & after several weeks becomes wonderfully hard & rigid; so much so that I could hardly from remove one off from its support.— On comparing a thin transverse slice of this petiole with one from the next below in succeeding unclasped or older leaf beneath, which its had not (Diagram 4) clasped anything, (its

[82v]

(a) ; in the hothouse it one was made to curve by a loop weighing 1.64 gr. & on the removal of the string, it became straight again.), but was not at all affected by another loop weighing 0.82 of a grain; with some leaf-climbers we have seen seen the the petioles of some other leaf-climbing genera affected by one-thirteenth of this latter weight.—

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diameter was found to be fully doubled, & In its structure greatly changed. In two other petioles similarly compared & here represented; the increase in diameter was not quite so great. (Diagram 4.)

In the section of the next petiole in its ordinary state (A.) we see a semilunar band of cellular tissue slightly different from that outside it, & including three closely approximate groups of dark vessels: on near the upper surface of the petiole, beneath two lateral ridges, there are two other small circular groups of vessels. In the section of the petiole (B.) which had clasped during several weeks a stick, the two upper ridges had become much reduced less prominent, & the two groups of woody vessels beneath them much increased in diameter.

The semilunar band was is converted into a complete ring of very hard, white woody tissue, with lines radiating from the centre. The three groups of vessels, which, though closely approximate were before

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distinct, are now completely blended together.

The upper part of this ring of woody vessels, formed by the prolongation of the horns of the semilunar band, is sho thinner than the lower part, & is slightly different in appearance from being less compact. This clasped petiole had actually become thicker than the stem or close beneath, & this was chiefly due to the greater thickness of the ring of wood having become thicker. I, which presented both in transverse & longitudinal sections a closely similar structure in the two cases or parts. petiole & axis

The assumption by a petiole of this structure is a singular morphological fact; but it is a still more singular physiological fact thatso great a change in structure should have been

should induced by the mere act of clasping a support.)

leading character structure of the, of the axis or stem, namely the closed woody ring of woody vessels

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— Adlumia & Fumaria are leaf-climbers; & so it is said are are same species of Corydalis; are likewise but the latter have true tendrils.—

Fumariaceæ.— Fumaria officinalis. It is surprising that could not have been anticipated that so lowly a plant should would have been a climber. This it effects by the aid of the main & lateral petioles of its compound leaves; even the much flattened & th terminal portion of the petiole acts can seize a support. I have seen so soft woll a substance as soft as a withered blade of grass caught. (a) On lightly rubbing with a twig several petioles they became perceptibly curved in 1° 15' & ultimately subsequently they straightened again themselves.

A stick gently placed in put into the angle between two sub petioles caused movement in 7°, & was almost clasped in 9°. A loop of thread, weighing 1/8 of a grain, caused in bef after 12° & before 20° had elapsed, a considerable curvature; but the petiole never fairly clasped by the thread. The internodes young shoot internodes are in continual movement, the movement is considerable, but very

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(a). Petioles which have clasped any support object ultimately become rather thicker & more cylindrical.

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irregular; being in course, forming a zigzag line, or a spire crossing itself, or a figure of eight: the course course being painted during 12° being traced on a bell-glass, apparently represented about four ellipses. This is a remarkable fact, observed in no other leaf-climber (for the case of Tropæolum tricolorum is rather different) that the main petioles of the leaves,

The leaves themselves also move spontaneously, the main petioles curving in accordance with the movement of the internodes; so that when the latter moves to one side the petiole is curved to that same side, then becoming straight is curved to the opposite side. & thus aids increase the sa

Thus a wider space is swept for a supporting object.─support to be clasped.─

This coursing of the petiole was rendered plain by painting a narrow line in its one side, when convex, & after a time the line became concave & then again convex.

again. The movement, however, is small; as could be seen, when the internode shoot was securely tied to stick & the leaf alone allowed allowed to move; the tendrils then fused & described then are thus alone it made the course

This then described an sort of irregular course like that as do that made described by the young internodes.) made by the young internodes.)

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Adlumia cirrhosa. — I raised some plants, late in the summer; they formed magnificent leav leaves, but threw up no central stem. The first-formed leaves were not sensitive; but some of the later leaves, though still rising only from the ground were sensitive, but only towards their extremities, & thus clasped sticks. This could be of no service to the plant, as these leaves rose from the ground, but it showed what the future character of the plant would be, when it had grown tall enough to climb. The tip of one of these ground leaves, whilst young, described a narrow ellipse, open at one end, in 1° 36; & exactly three inches in length; a second ellipse was broader, shorter & more irregular, & shorter, & viz., only 2 1/8 of an inch in length, & was perform completed in 2° 2'. From the analogy of Fumaria & Corydalis, I have no doubt that the internodes would when formed would have been revolved.)

Corydalis claviculata. — This plant is interesting from being so exactly intermediate condition between a leaf-climber & a tendril-bearer, that it might have been have been described here under either head; but, for reasons

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hereafter assigned, it is placed classed amongst the Tendril bearers.

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(Besides the plants already described, Bignonia unguis & its close allies, though aided by tendrils, ─ will hereafter be described, climbs by sensitive have clasping petioles. According to Mohl (s. 40) Cocculus Japonicus (one of the Menispermaceæ) and a fern, the Ophioglossum Japonicum (s. 39) alone climb by the aid of by their leaf-stalks.)

(We now come to the a small section of plants which climb by the aid of the produced midribs or tips of their leaves.)

Gloriosa Plantii (Liliaceæ). The summit of the stem, after the of a half-grown plant has grown a little height continually moved, generally describing an irregular spire, but sometimes ovals with the longer axis running in different directions. It either followed the sun or moved in reversed the an opposite course, it sometimes stands stood still before reversing its course. One oval was completed in 3° 40'; another two horseshoe-shaped revolutions figures, one in 4° 35', & a thread & the other in 3°.

The tip of the shoot extreme points reached by the summit of the moving shoots were tip ofshoot, in its movements reached points from four and five inches

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asunder. The young leaves, when first developed, stand up nearly vertically; but by the growth of the axis, & by the spontaneous bending down of the terminal half of the leaf, they soon become much inclined, & ultimately they become horizontal. The end of the leaf forms a narrow, ribbon-like, thickened projection, which at first is nearly straight, but by the time the leaf has got into an inclined position, the terminal end has become curved downwards bent itself downwards into a regular well-formed hook; & this has become so is now strong & rigid that when it catches enough to catch any object, & and to when this is effected to anchor the plant & stop so that it stops the the irregular revolving revolving movement is stopped.

The hook is sensitive, on the its inner surface; but not in nearly so high a degree as the before described petioles; for a loop of string, weighing 1.64 gr. produced no effect. But when the hook catches a thin twig or even a rigid fibre, the point may be perceived in from 1° to 3° to have curled a little inwards; & in from 18° to 20° under favourable circumstances in from 8° to 10° it firmly seize curls round & seizes the object, which is never again loosed.─ The hook, whilst young when first formed, before the whole leaf has become inclined

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is much less sensitive, & as such moves more slowly.

The hook, if it catches hold hold of nothing, long remains for a long period open & sensitive; ultimately the tip spontaneously & slowly curls inwards, & makes a button-like, flat spiral coil at the end of the leaf. One leaf was watched, & the hook remained open for 33 days; but during the last week the tip had curled inwards so much that at last only a very thin twig could have been caught inserted. so As soon as the curling in of the tip has closed the hook, & made a ring, & its sensibility is lost, both within & without, the still open now formed ring thus formed, is lost; but as long as the hook as it remains at all open open its retain its sensitivity is retained.) Once on one occasion, I placed a stick so that it lightly lightly passed did not touch the hook, but by lightly passed against the under side of the attenuated terminal half of the leaf; this part did not bend, but by sympathy & without contact the hook tip of the hook slowly & slightly curled inwards & formed a ring which retained its sensibility.)

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& the ring thus formed & not spontaneously formed due to by age retained its sensibility.)

When the plant had grown from the bulb to a height of about to a height six inches in height, the leaves leaves, four or five in number, were broader broader than those subsequently produced; & their soft & but little attenuated tips did not form hooks & were not sensitive: at no not the axis stem perform its revolving movements ; nor did the stem revolve. At this early period of growth, the plant can support itself; & its climbing apparatus not required & therefore is not therefore possessed acquired. In one On the other hand, in one a full-grown plant, which was flowering, & would not grow grow any height latter, & therefore would not require to climb the young attenuated young leaves on the summit had did not possess any sensibility, & could not clasp a stick.)

Flagellaria Indica. — (Commelynaceæ.) From dried specimens which I have seen it is manifest that this plant climbs exactly like the Gloriosa. A young plant twelve inches in

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height & bearing 15 leaves, had not a single leaf as yet produced into a hook or tendril-like f filament; nor did the stem revolve. Hence this plant acquires its climbing powers later in life than does the Gloriosa lily. According to Mohl (s. 41), Uvularia (Melanthaceæ) also climbs like Gloriosa.) (These three last-named genera here mentioned are all endogenus endogenus monocotyledons but there is one exogenus exogenus genera dicotyledon, namely nepenthes, (a) which from what Mohl says & from what I have heard from other quarters, certainly climbes by the tips of its leaves; my plants were not sufficiently vigorous vigorous to allow me to make observations on on them.

Summary on Leaf-climbers. — Plants belonging to eight Families sensitive petioles, both main medial & lateral petioles, when such occur the latter are present: and plants belonging to five families to climb have climb by the tips of their leaves. sensitive & climb by their aid. With all these the plants, which have been were observed by me, the young internodes revolved more or less regularly,

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likewise becomes thickened. Two vigorous young plants of N. lævis & distillatoria, whilst under a foot in height, showed no sensitiveness in their leaves, or power of movement or of climbing. But when N. lævis had grown to a height of 16 inches, there were signs of these powers. Each young leaves when first formed stood vertically up & stands upright, but soon afterwards become inclined; ultimately almost horizontal: it ended terminate in a stalk or filament, or tendril with the pitcher at the extremity so little developed, that this part was is not thicker than any other part. The leaf in this state certainly exhibited slight spontaneous movements; & when the stalk came into contact by its lateral or under surface with a stick, it very slowly bent round & firmly seized it. But the leaf by its subsequent growth became quite slack, though the still terminal stalk remained attached the stick; hence it would appear, that the chief service of the attachment, at least whilst the plant is young, is to support the pitcher with its load of secreted fluid.)

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(a) which is ranked by Mohl (s. 41) amongst tendril-bearers & I hear from Dr. Hooker that some of most of the species climb well at Kew. This is effected by the stalk between the leaf & the pitcher, which twisting round any support becomes thicker, when twisted.

The twisted part becomes when thicker; but I observed in Mr. Veitch's that the stalk often became twisted, without takes a turn when not not in contact with any object & that this part was likewise becomes thickened, I presume that these plants are enabled to climb only when* old; after having grown to some height for I had healthy young plants of N. lævis & distillatoria, & I could detect no distinct well-marked signs of sensitiveness or of spontaneous movements in the stalks.)

between the leaf & pitches.

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generally rather quickly, in some cases, as regularly as does any twining plant, & generally at a at different various rates, but generally rather rapidly. rates (a) Differently from most twiners, there is a strong tendency in the same shoot to follow revolve first in one direction & then in another the opposite direction. The object gained by the revolving movement, as could be plainly seen, was the bringing the petioles or the tips of the leaves into contact with a supporting surrounding objects: with one exception, the The petioles in all cases are sensitive on all sides. With rare exceptions, the young petioles alone are sensitive only whilst young: & then they are generally sensitive on all sides, but in different degrees in different plants plants; & in Clem some some species of Clematis differently Clematis in different degrees in different parts of the same petiole. (B) They are sensitive to a touch & to excessively slight continued pressure, even to a loop from a loop of soft thread weighing only the 1/16th of a grain; & there is reason to believe that the rather thick & f stiff petioles of Clematis flammula are sensitive to even a less weight, when spread over a wider surface. After a petiole The petioles invariably

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(a) Some few of these plants can irregular twin spirally round a support.

(b) The hooked tips of the leaves of the Gloriosa are sensitive only in their inner & inferior surfaces. The petioles

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shoot bend slowly toward the touched or pressed side, at different rates in different plants, sometimes within a few minutes, but generally after a much longer period. After temporary contact with any object, the petiole continues to bend for a considerable time; The bending continues for a after temporary contact the bending continues for a considerable time, & then afterwards the petiole slowly becomes straight again,; it it can bend then act again. If a petiole excited by an extremely slight weight sometimes sometimes causes a petiole to bend a little, & will bends a little, & then becomes habituated to the stimulus stimulus, & either bends no more or becomes straight again. Petioles which have clasped any object for some little time cannot recover recover their original position. After remaining clasped for two or three days they generally increase much rapidly in thickness either at on one side or throughout, & become always become straight & more woody; sometimes in a wonderful degree stronger & more woody; they stand in the [illeg] & assume like internal structure; they ultimately assume in some cases the same internal structure with that of [illeg] the an stem or axis.)

(In one the case The young internodes of the Lophospermum are sensitive as well as the petioles, In the case of the Fumaria & Adlumia the petioles, as well as the internodes, spontaneously move curve curve from side to side. With Tropæolum tricolorum the petioles, bearing rudimentary leaves, as they grew old moved moved spontaneously towards toward the stem

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(a)

and by theircombined movement can seize an object. The flower-peduncles of the Maurandia semperflorens revolve spontaneously & are sensitive to a touch, but yet are certainly useless for climbing. The whole leaf of at least one & probably of several species of Clematis, of Fumaria & Adlumia rar move from spontaneously curve from side to side or revolve, like the internodes, & are thus better adapted to seize a more distant objects. The petioles of the perfect leaves, as well as of the rudimentary or tendril-like leaves of Tropæolum tricolorum move slowly & spontaneously towards their own stem or the supporting stick, which they then clasp. These petioles, likewise also show some tendency

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& showed showed some tendency to contract spirally. The tips of the uncaught leaves of the Gloriosa, as they grow old, likewise contract into a flat spire or helix. These several facts are interesting; as we shall see, in relation to true tendrils.

In some cases, it was observed with twining plants, so with leaf-climbers, the first internodes which rise from the ground do not move spontaneously revolve; nor are the foo petioles or tips of the leaves first-formed leaves sensitive.

In certain species of a genus, are which are not climbers Clematis, the high development of the leaves or bas with their highly sensitive petioles apparently bend to the contact & be then lead to has rendered almost superfluous, the enfeeblement of the spontan spontaneous movement of the internodes which has consequently become feeble In some certain

In certain species of Tropæolum, it would appear that as if the spontaneous movement of the internode & the sensitiveness of the petioles had either both become enfeebled, one has been quite lost & in other one species had been completely lost.—