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[blue sheet on pale blue backing sheet (CUL-DAR61.18):]

(a)

(I also placed as already stated four flies, on single the glands of the marginal hairs & then of three were moved carried to the centre of the leaf in 35 minutes to an ∠ of 180; the fourth was which was extremely minute was was carried in 3 hours; over in through two 1° 30' 1 ½ hours. (Z) I then placed four little bits of cinder placed on single marginal hairs; one of these in 3° 40' reached the centre in 3° 40'; a second in 9°; a third had moved someway only part of the way towards the centre in the nine hours; the fourth in 24° had moved a only short distance: not one of the four three bits of cinder which had reached the centre were after 24° well enclosed; in fact only two or three hairs glands on each leaf besides that which carried the atoms, had enclosed come in contact with it. (D.) Much which had been placed on marginal hairs   all  Whereas in of the case of the seven flies all carried never quickly to the centre were well enclosed   by nearly all the hairs on said leaf   in form four to ten hours, after being having been first placed on the glands, of marginal hairs. These facts

[on backing sheet '19':]

on the action of single hairs likewise strongly support the conclusion that [illeg] substances affect nutritious & innutritious substances placed on the glands of single hairs, effect  act on  them, differently.)

(Being As I was more surprised at what to  small [illeg] atoms of the above named & other substances placed on the gl which caused single hairs [illeg] to move have altered, I thought it seemed worth trying altering how little small more a weight partial would act.— to  the I place the substance on the cut off atoms little bits of a narrow blall slip of blott-paper, ,of the finest cotton-thread, & of a woman's hair, I had it cut off one per & after the atoms had plainly [caused]  [illeg], I carefully measure their length with a micrometer: I

[See Insectivorous plants, pp. 26-27.]

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Z/

of six little balls of paper rolled up with pincers & placed on marginal glands these were carried to the centre in one hour & the other three in rather more than four hours: of these only two were after 24 hours were well embraced by the on all the hairs round

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(11B

them measured several inches of the same thread hair & paper, & Mr. Trenham Reeks¹ carefully weighed me for them for me in Jermyn St with an excellent balance; thus it was very easy to calculate length the weight of the atoms.

I placed these atoms on the glands, by [illeg] By moistening the point of a fine needle with water I placed under microscope I place them the atoms in the sticky secreted viscid fluid & secreted by the glands so that I am positive I did not touch the gland itself. At

The A bit of blotting paper weight 1/465 of a grain, itself but as it rested at the [2 words illeg]  on three glands & then at three hairs all later slowly would curled in curled inwards; so that each could have been pressed by any 1/1395 of a grain. Five all of each    The least atoms piece  (for four were tried five of [3 words illeg] of cotton-thread (for five of nearly equal length were tried & all acted.) weighed 1/8197 of a grain; & this caused the hairs glands [illeg] to be considerably inflected in 1°. 30' & in 4°. 30' to be carried to the centre of the leaf; much of the other atoms of thread were moved round rather less quickly more slowly. Lastly two atoms of the thinner end of a human woman's hair, [illeg] 18/1000 18/1000 & 19/1000 an inch in length, ([c. 4 words illeg] slightly longer atoms) caused the two hairs glands on the last leaf to move out of their regular rank & become inflected half way towards the centre of the leaf in 1° 10'; every all the other glands round the leaf remaining in their proper rank or & expanded position. & as This atom of hair weighed less than the 1/35,000 of a grain. Not only was the inflection of the footstalk of which glands in this above several cases conspicuously plain, but changed took place in the [4 words illeg] cells of the a footstalk. [2 words illeg] hereafter to be more intelligible described, which were so plain [illeg], that I could readily have picked out under the microscope the glands & footstalks tentacles which

Hair at [illeg]

¹ Trenham Reeks (1823/4-1879), mineralogist, Curator and librarian of the Jermyn Street institution, London, 1851-1899. He examined mineral substances Darwin collected during the voyage of the Beagle. The weight of thread, hair and paper was communicated to Darwin in a letter from 15 November 1860. (Correspondence vol. 17) This was cited in Insectivorous plants, p. 27.

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(11 C

had carried which then [illeg] weight loads from the any atoms hundred of the & upwards glands & footstalk with which each leaf was furnished base & which had not moved.) [3 faint pencil lines illeg]

I was [2 words illeg] of a [illeg]

(At first I thought that it could not be the weight, but the [illeg] nature of the substances placed on the glands which caused the movement, but as bits of mea flies, raw meat, fire-wood, cork, common common [illeg] & blotting paper, black cinder lately taken from the fire, [illeg] of [illeg] & [illeg] glass cotton thread & human hair gold-leaf all caused the movement, this idea cannot be maintained. It cannot be the shadow for the leaves contraction takes places in the dark as well as in the light; [c.5 pencil words illeg] ([3 words illeg] & the human hairs were only [illeg] in diameter, whereas the gland is about1/400 of one inch in diameter).

(Boiling)

It cannot be the absorption of the secreted viscid fluid secreted by the gland, for moist raw meat & the a first hair acted as well as the [illeg] blotting paper

[inserted pencil line largely illeg]

(a) ; Moreover I removed with a pointed piece of blotting-paper, (p 116 all or nearly all the viscid secretion from six glands; & though thus for a exposed pure [2 words illeg] to the air they were [3 words illeg] not inflected in during 24 hours; I subsequently tested these glands with atoms of raw meat & they acted well. As in some at least of the experiments with alone of hair, the atoms of hair remained only partly immersed in the viscid secretion, & as far as I could judge did not touch the gland itself, I thought that the distortion of the spherical drop of secretion, surrounding the gland might be the cause of inflection; but this seems hardly [illeg] considering that the whole or nearly the whole of the secretion may be removed by blotting paper without causing inflection: moreover two adjoining glands frequently stand so near each other, that these drops of secretion touch & become drawn out, but this does not cause any inflection. We thus seemed forced to the conclusion that it must be the weight along of the atoms, excessively little as this weight is, which causes the movement. Should it ever be proved not to be weight we anyhow see that excessive minute atoms in size are plainly sufficient to cause movement.)

[22v]

[6 words illeg])

 I was more My surprise was [excised]

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11D

(The action of the weight must be prolonged for some time to cause movement. A slight touch with a fine camel-pencil produces no effect. I tried, also, simply touching 45 glands an eleven different leaves with a strong needle & likewise with a short & stiff bristle: some I touched two or three times, some only once, but in any case quickly & with sufficient force to bend down the pedicel of hair; & I often removed [illeg] of the viscid secretion: of the 45 hairs thus merely touched, with a force at least a thousand [illeg] more than the weight of the [illeg] atoms, which hardly [illeg] the viscid secretion, this alone became plainly inflected & thus others in a very slight degree: of the 18 glands touched mostly with the stiff short bristle only can become inflected in a slight degree, some of the hairs, about 10 in number which did not become inflected I tested with by placing on these atoms of meat & they in due time became inflected. The necessity of the actions of the weight to be prolonged in order to cause [illeg] in the hairs, seem [2 words illeg] to be a beautiful adulteration provision in relation to the economy of the plant; for on

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in windy day the hairs must often be touched by it surrounding leaves & if they closed the action could be in vain; but if even a gnat alights with its delicate tarsi one xx on each glands, & in them being retained on them by the viscid secretion the weight excessively small as it must be suffices to cause the insect to be carried to the centre & thought to be embraced by all the hairs of the leaf. We must not, however, exaggerate the perfection of the action adaptation: for if a seed or bit of moss falls on the leaf, it is becomes as I have often seen, well though varying embraced; but it is released much

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(11 D E

Sooner than if it had been a nutritious fly.

Nor need we be so much surprised at such minute weight acting on the glands, when we remember that the smaller animals feed on & therefore must feel infusoria invisible to the naked eyes; & sensitive in thought believed to imply changes in the nervous matter. Nevertheless with plants it is certainly a remarkable fact that a weight of an atom weighing less than [illeg] less than 1/78,000 of a grain (nor do we know that there is minimum weight which [illeg] act) should cause plain movement & changes in structure in a plant; this weight being seventy-eight times less than that which will turn with certainty the best balances made used in our laboratories.) What the minimum weight which will cause movement I have not ascertained, but I have often observed [illeg] atoms of dust on the glands which had produced no effect.)

(Fluids)

Drops of water even from some height [2 words illeg]

Curling of heads.

Cells of all plants [c.6 words illeg] (Cohn)

in all the [illeg] of the plants, must have been acquired during long ages to showers of rain, & [illeg] were [6 words illeg] descendant [illeg] [many words illeg] (Cohn)

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(11 E F

Fluids

(Reflecting on this several factors now given, circumstances, namely to such number of flies caught, the manner in which the are carried    more especially in the case of the marginal hairs,   to the centre of the disc, & are then bathed by the secreted fluid, it seemed to me almost certain highly probably that something was absorbed from these dead bodies bed bodies, & act of absorption caused the hairs to move more quickly & to remain so much longer clasped over flies [calculations] than over vegetable or mineral substances, &

[archivist's comment: '(Ch V; pp.76ff)' noting the similarity with Insectivorous plants, pp. 76-77.]

There remained also on my mind some slight doubt whether a difference as to weight of the different dry & damped substances could have caused to difference in the actions of the hairs; but under all the circumstances not worth specifying this seemed scarcely possible. Nevertheless Hence it seemed occurred to me that a comparison of the effect of nearly as possible equal sized drops of various nitrogenous & non nitrogenous fluids of different [3 words illeg] would clear up    I [words illeg]  the points; (see p 12) [words illeg] & the results of the following experiment seem to me decisive, that the absorbent glands of the leaves do are capable of absorbing & discriminating most nitrogenous compounds & move in consequence of this absorption.   & I believe this fact to be new in vegetable physiology.—         I at first thought any [illeg], when care must reading to hand[?]