The Power of Movement in Plants

A atte traced from 8 a.m. July 3rd pended, is the same as in the o 10.15 a.m. 4th. ‘Temp. : movement greatly mag- C1.) Sarracenia purpurea (Sarra- pified. y : cenee, Fam. 11).—A young leaf, or pitcher, 83 inches in height, with the bladder swollen, but with the hood not as yet open, had a filament fixed transversely across its apex ; it was observed for 43h., and during the whole of this time it circumnutated in a nearly similar manner, but Glauctwn luteum: circumnuta- tion of young leaf, traced from 9.30 a.M. June 14th to 8.39 a.m. 16th. Tracing not much magnified, as apex of leaf stood only 5} inches from the glass.

(2.) Glaucium luteum (Papave- race, Fam. 12).—A young plant, bearing only 8 leaves, had a fila- ment attached to the youngest leaf but one, which was 3 inches in length, including the petiole. The circumnutating movement was traced during 47 h. On both days the leaf descended from before 7 a.m. until about 11 am., and then ascended slightly during the rest of the day and the early part of the night. During the latter part of the night it fell greatly. It did not ascend so much during the second as during the first day, and it descended considerably lower on the second night than on the first, This difference was probably due to the illumination from above having been insufficient during the two days of observation. Its course during the two days is shown in Fig. 94.

(8.) Crumbe maritima (Crucifere, Fam.14).—A leaf 93 inches in length ona plant not growing vigorously was first observed. Its apex was in constant movement, but thie could hardly be traced, from being sosmall in extent. The apex, how- ever, certainly changed its course at least 6 times in the course of 14h. A more vigorous young plant, bear- ing only 4 leaves, was then selected, and a filament was affixed to the midrib of the third leaf from the base, which, with the petiole, was 5inchesinlength. The leaf stood up almost vertically, but the tip

was deflected, so that the filament projected almost horizontally, and its movements were traced during 48 h. on a vertical glass, as shown in the accompanying figure (Fig. 95). We here plainly sive nights, and they were found at this latter hour to have risen by an average angle of 9° above their mid-day position: : on the following morning y they fell to their former i position. Now it may be 6°50! am. 24th observed in the diagram that the leaf rose during the second night, so that it stood at 6.40 a.m. higher Spinzdth than at 10.20 p.m. on the Crambe maritima: circumnutation of leaf, preceding night; and this disturbed by being insufficiently illumi-

- nated from above, traced from 7.50 a M. may be attributed to the June 23rd to 8 AM. 25th. Apex of leaf leaf adjusting itself to the 15} inches from the vertical glass, so that dim light, coming exciu- the tracing was much magnified, but is sively from above. here reduced to one-fourth of original scale. (4.) Brassica oleracea (Cruciferee).—Hofmeister and Batalin * state that the leaves of the cabbage risc at night, and full by day. We covered a young plant, bearing 8 leaves, under a large bell-glass, placing it in the same position with respect to the

light in which it had long remained, and a filament was fixed at the distance of ‘4 of an inch from the apex of a young leat nearly 4 inches in Jength. Its movements were then traced during three days, but the tracing is not worth giving. The leaf fell during the whole morning, and rose in the evening and during the early part of the night. The ascending and descend- ing lines did not coincide, so that an irregular ellipse was formed each 24h. The basal part of the midrib did not move, as was ascertained by measuring at successive periods the angle which it formed with the horizon, so that the movement was confined to the terminal portion of the leaf, which moved through an angle of 11° in the course of 24 h., and the distance travelled by the apex, up and down, was between °8 and °9 of an inch.

In order to ascertain the effect of darkness, a filament was fixed to a leaf 5: inches in length, borne by a plant which after forming a head had proiuceda stem. The leaf was inclined 44° above the horizon, and its movements were traced on a vertical glass every hour by the aid of a taper. During the first day the leaf rose from 8 a.m. to 10.40 pw. in a slightly zigzag course, the actual distance travelled by the apex being 67 of an inch. During the night the leaf fell, whereas it ought to have risen; and by 7 a.m. on the following morning it had fallen +23 of an inch, and it continued falling until 9.40 a.x. It then rose until 10.50 p.m., but the rise was interrupted by one considerable oscillation, that is, by a fall and re-ascent. During

-the second night it again fell, but only to a very short distance, and on the following morning re-ascended to a very short distance. Thus the normal course of the leaf was greatly disturbed, or rather completely inverted, by the absence of light; and the movements were likewise greatly diminished in amplitude. We may add that, according to Mr. A. Stephen Wilson,* the young leaves of the Swedish turnip, which is a hybrid between B. oleracea and rapa, draw together in the evening so much “that the horizontal breadth diminishes about 30 per cent. of the daylight breadth.” Therefore the leaves must rise con- siderably at night.

* ‘Trans. Bot. Soc. Edinburgh,’ — see Darwin. * Animals and Plants vol. xiii. p. 32. With respret to under Demestication, 2nd edit the origin of the Swi dish turnip, vol. i. p. S44, : terminal shoot of a young plant, growing very vigorously, was selected for observation. The young leaves at first stand up vertically and close together, but they soon bend outwards and downwards, so as to become horizontal, and often at the same time a little to one side. A filament was fixed to the tip of a young leaf whilst still highly inclined, and the first dot was made on the vertical glass at 8.30 a.m. June 13th, but it curved downwards so quickly that by 6.40 a.m. on the following morning it stood only a little above the horizon. In Fig. 96

Dianthus caryophyllus: circumnutation of young leaf, traced from 10.15 P.M. June 13th to 10.35 p.br. 16th. Apex of leaf stood, at the close of our observations, 82 inches from the vertical glass, so tracing not greatly magnified. The leaf was 53 incheslong. Temp. 15$°-172° C. the long, slightly zigzag line representing this rapid downward course, which was somewhat inclined to the left, is not given; but the figure shows the highly tortuous and zigzag course, together with some loops, pursued during the next 23 days. As th: leaf continued to move all the time to the left, it ig evident that the zigzag line represents many circumnutations, (6.) Camellia Japonica (Camelliaceee, Fam. 32)—A youngish leaf, which together with its petiole was 2% inches in length and which arose from a side branch on a tall bush, had a filament attached to its apex. This leaf sloped downwards at an angle of 40° beneath the horizon. As it was thick and rigid, and its

Camellia Japonica: cir- cumnutation of leaf, traced from 6.40 A.M. June 14th to 6.50 AM. 15th. Apex of leaf 12 inches from the ver- tical glass, so figure considerably = mag~- nified. Temp. 16°- much movement could not be expected Nevertheless, the apex changed its course completely seven times in the course of 114 h., but moved to only a very sma) distance. On the next day the movement of the apex was traced during 26 h. 20 m. (as shown in Fig. 97), and was nearly of the same nature, but rather less complex. The movement seems to be periodical, for on both days the leaf cireumnutated in tho forenoon, fell in the afternoon (on the first day until between 3 and 4 p.m., and on the second day until 6 p.m.), and then rose, falling again during the night or early morning.

we shall see that the leaves in several Malvaceous genera sink Pelargonium zonale: circumnutation and downward movement of young leaf, traced from 9.30 A.M. June 14th to 6.30 p.m. 16th. Apex of leaf 9} inches from the vertical glass, so figure moderately magnified. at night ; and as they often do not then occupy a vertical position, especially if they have not been well illuminated during the day, it is doubtful whether some of these cases onght nat to have been included in the present chapter.

(7.) Pelargonium zonale (Geraniacee, Fam. 47).— A young leaf, 1} inch in breadth, with its petiole 1 inch long, borne on a young plant, was observed in the usual manner during 61 h.; and its course is shown in the preceding figure (Fig. 98). During the first day and night the leaf moved downwards, but circumnutated between 10 a.m. and 4.30 p.m. On the second day it sank and rose again, but between 10 a.m. and 6 p.m. it circumnutated on an extremely small scale. On the third day the circumnutation was more plainly marked.

full-grown, the third from the apex of Fig. 99. a shoot on a cut-down plant, was observed during 31h. 30 m. (see Fig. 99). The day was cold (15°-16° C.), and if the plant had been observed in the hot-house, the circumnutation, though plain enough as it was, would probably have been far more cou- spicuous. (9.) Vicia faba (Leguminose, Fam. 75)—A young leaf, 3:1 inches in length, measured from base of petiole to end of leaflets, had a filament affixed to the midrib of one of the two ter- minal leaflets, and its movements were : traced during 513 h. The filament fell we all morning (July 2nd) til 3p.mj,and 6... ai, adler 2eivouriuc then rose greatly till 10.35 p.m.; but tation of leaf, traced the rise this day was so great, com- from 10.35 aM. May pared with that which subsequently ai ae ee oe

: z Apex of leaf 83 inches occurred, that it was probably due in from the vertical glass, part to the plant being illuminated from above. The latter part of the course on July 2nd is alone given in the following figure (Fig. 100). On the next day (July 8rd) the leaf again fell in the morning, then circumnu- tated in a conspicuous manner, and rose till late at night; but the movement was not traced after 7.15 p.m., as by that time the filament pointed towards the upper edge of the glass. During the latter part of the night or early morning it again fell in the same manner as before.

As the evening rise and the early morning fall were unusually large, the angle of the petiole above the horizon was measured at the two periods, and the leaf was found to have risen 19° Vieia fbi; circumnutation of leaf, traced from 7.15 p.m. July 2nd te 10.15 A.M. 4th. Apex of the two terminal leaflets 7} inches from the vertical glass. Figure here reduced to two-thirds of original scale. Temp. 17°-18° C. between 12.20 p.m. and 10.45 p.m., and to have fallen 23° 380 between the latter hour and 10.20 a.m. on the following morning. The main petiole was now secured to a stick close to the base

of the two terminal leaflets, which were 1°4 inch in length; and the movements of one of them were traced during 48h. (sce Fig. 101). The course pursued is closely analogous to that of the whole leaf. The zigzag line between 8.380 a.m. and 3.30 P.a. on the second day represents 5 very small ellipses, with their Vicia faba: circumnutation of one of the two terminal leaflets, the main petiole having been secured, traced from 10.40 a.m. July 4th to 10.30 a.m 6th. Apex of leaflet 63 inches from the vertical glass. Tracing here reduced to one-half of original scale. Temp, 16°-18° C.

longer axes differently directed. From these observations it follows that both the whole leaf and the terminal leaflets undergo a well-marked daily periodical movement, rising in the evening and falling during the latter part of the night or early morning; whilst in the middle of the day they generally circumnutate round the same small space. (10.) Acacia retinoides (Leguminose).—The movement of a young phyllode, 23 inches in length, and inclined at a consider-

Acacia retinoides : cir- cumnutation of a young __ phyllode, traced from 10.45 aM. July 18th to 8.15 aM. 19th. Apex of phyllode 9 inches from the vertical glass; temp. able angle above the horizon, was traced during 45 h. 30 m.; but in the figure here given (Fig.102), its circumnutation is shown during only 21h. 30m. During part of this time (viz., 14 h. 30 m.) the phyllode described a figure re- presenting 5 or 6 small ellipses. The actual amount of movement in a ver- tical direction was *3 incb. The phyllode rose considerably be- tween 1.30 p.m. and 4 pm., but there was no evidence on either day of a regular pe- riodic movement. C11.) Lupinus sye- ciosus (Leguminose).

—Plants were raised from seed purchased under this name. This is ove of the species in this large genus, the leaves of which do not sleep at night. The petioles rise direct from the ground, and are from 5 to 7 inches in length. A filament was fixed to the midrib of one of the longer leaflets, and the movement of the whole leaf was traced, as shown in Fig. 108. In the course of 6 h. 30 m. the filament went four times up and three times down. A new tracing was then begun (not here given), and during 123 h. the leaf moved eight times up and seven times down; s0 that it described 73 ellipses in this time, and this is an extraordinary rate of movement. The summit of the petiole was then secured

to a stick, and the separate leaflets were found to be continnally (12.) Echeveria stolunifera (Crassulacese, Fam. 84).—The older leaves of this plant are so thick and fleshy, and the young ones so short and broad, that it seemed very improbable that any circum- nutation could be detected. A fila- ment was fixed to a young upwardly inclined leaf, °75 inch in Jength and °28 in breadth, which stood on the outside of a terminal rosette of leaves, produced by a plant growing very vigorously. Its movement was traced during 3 days, as here shown (Fig. 104). The course was chiefly in an upward direction, and this may be attributed to the elongation of the leaf through growth; but we see that the lines are strongly zigzag, and that al occasionally there was distinct cir- f

cumnutation, though on a very small Echeceria stolonifera : circum- scale nutation of leaf, traced cl fe calycinum (Crassulacese).— Duval- of leaf 12} inches from the Jouve (Bull. Soc. Bot. de France, — 8s; s0 ie oe ea eine Feb. 14th, 1868) measured the diss Qy0049G tance between the tips of the upper pair of eaves on this plant, with the result shown in the following Table. It should be noted that the measurements on Dec, 2nd were made on a different pair of leaves :—

We see from this Table that the leaves stood considerably further apart at 2 p.m. than at either 8 am. or7 p.M.; and this shows that they rise a little in the evening and fall or open in the forenoon. (14.) Drosera rotundifolia (Droseracese, Fam. 85).—The move- ments of a young leaf, having a long petiole but with its tentacles (or gland-hearing hairs) as yet unfolded, were traced during 47h. 15m. The figure (Fig. 105) shows that it cireumnutated largely, chiefly in a vertical direction, making two ellipses each

Drosera rotundifolia: circumnutation of young leaf, with filament fixed to back of blade, traced from 9.15 A.M. June 7th to 8.35 a.m. June 9th. Figure here reduced to one- half original scale. very unequal distance on the two occasions. We therefore thought that the movement was periodic; but on observ- ing three other leaves during several successive days and nights, we found this to be an error; and the case is given merely as a caution. On the third morning the above leaf occupied almost exactly the same position as on the first morning; and the tentacles by this time had unfolded sufficiently to project at right angles to the blade or disc. The leaves as they grow older gencrally sink more and more downwards. The movement of an oldish leaf,

still secreting freely, was traced for 24 h., during which time it continued to sink a little in a slightly zigzag line. On the following morning, at 7 A.M., a drop of a solution of carbonate of ammonia (2 gr. to 1 oz. of water) was placed on the disc, and this blackened the glands and in- duced inflection of many of the tentacles. The weight of the drop caused the leaf at first to sink a little; but immediately afterwards it began to rise in a somewhat zigzag course, and continued to do so till 8p.m. It then circumnutated about the same spot on a very small scale for 21 h.; and during the next 21 h. it sank in a zigzag line to nearly the same level which it had held when the ammonia was first administered. By this time the tentacles had re-expanded, and the glands had recovered their proper colour. We thus learn that an old leaf

circumnutates on a small scale, at least whilst absorbing car- bonate of ammonia; for it is probable that this absorption may stimulate growth and thus re-excite circumnutation. Whether the rising of the glass filament which was attached to the back of the leaf, resulted from its margin becoming slightly inflected (as generally occurs), or from the rising of the petiole, was not ascertained. In order to learn whether the tentacles or gland-bearing hairs circumnutate, the back of a young leaf, with the innermost tentacles as yet incurved, was firmly cemented with shellac to a flat stick driven into compact damp argillaceous sand. The plant was placed under a microscope with the stage re- moved and with an eye-piece micrometer, of which each division equalled 54, of an inch, It should be stated that as the leaves grow older the tentacles of the exterior rows bend outwards and downwards, so as ultimately to become deflected considerably beneath the horizon. A tentacle in the second row from the margin was selected for observation, and was found to be moving outwards at a rate of 335 of an inch in 20 m., or z35 of inch in 1 h. 40 m.; but as it likewiso moved from side to side to an extent of above <4, of inch, the move- ment was probably one of modified circumnutation. A tentacle on an old leaf was next observed in the same manner. In 15 m. after being placed under the microscope it had moved about yg55 Of an inch. During the next 73 h. it was looked at repeatedly, and during this whole time it moved only another tooo Of an inch ; and this small movement may have been due to the settling of the damp sand (on which the plant rested), though the sand had been firmly pressed down. We may there- fore conclude that the tentacles when old do not circumnutate ; yet this tentacle was so sensitive, that in 23 seconds after its gland had been merely touched with a bit of raw meat, it began to curl inwards. This fact is of some importance, as it appa- rently shows that the inflection of the tentacles from the stimulus of absorbed animal matter (and no doubt from that of contact with any object) is not due to modified circumnutation.

(15.) Dioncea muscipe.la (Droserace).—It should be premised that the leaves at an early stage of their development have the two lobes pressed closely together. These are at first directed back towards the centre of the plant; but they gradually rise up and soon stand at right angles to the petiole, and ultimately in nearly a straight line with it. A young leaf, which with the 240 CIRCUMNUTATION OF LEAVES. Cuap. IV petiole was only 12 inch in length, had a filament fixed exter- nally along the midrib of the still closed lobes, which projected at right angles to the petiole. In the evening this leaf com- pleted an ellipse in the course of 2h, On the following day (Sept. 25th) its move- ments were traced during 22 h.; and we see in Fig. 106 that it moved in the same general direction, due to the straightening of the leaf, but in an extremely zigzag line. This line represents several drawn-out or modified ellipses. There can therefore be / no doubt that this young leaf circumnu~-

; A rather old, horizontally extended ! leaf, with a filament attached along the f under side of the midrib, was next observed during 7 h. It hardly moved, but when one of its sensitive hairs was touched, the blades closed, though not very quickly. A new dot was now made on the glass, but in the course of 14h. 2) m. there was hardly any change in the position of the filament. We may therefore infer that an old and only moderately sensitive leaf does not cireum- nutate plainly; but we shall soon see

cumnutation of a young and expanding leaf, traced on a hori- zontal glass in dark- ness, from noon Sept. 24th to 10 a.m. 25th. Apex of leaf 13} inches from the glass, so tracing consider- ably magnified. that it by no means follows that such a leaf is absolutely motionless. We may further infer that the stimulus from a touch does not re-excite plain circumnu- tation. Another full-grown leaf had a filameni attached externally along one side of the midrib and parallel to it, so that the fila- ment would move if the lobes closed. It

should be first stated that, although a touch on one of the sensi- tive hairs of a vigorous leaf causes it to close quickly, often almost instantly, yet when a bit of damp meat or some solution of carbonate of ammonia is placed on the lobes, they close so slowly that generally 24 h. is required for the completion of the act. The above leaf was first observed for 2 h. 30 m., and did not circumnutate, but it onght to have been observed for a longer period; although, as we have secn, a young leaf com- pleted a fairly large ellipse in 2 h. A drop of an infusion of raw meat was then placed or the leaf, and within 2 h. the glass filament rose a little; and this implies that the lobes had begun to close, and perhaps the petiole to rise. It continued to rise with extreme slowness for the next 8 h. 30m. The position of the pot was then (7.15 p.m., Sept. 24th) slightly changed and an additional drop of the infusion given, and a new tracing was begun (Fig. 107). By 10.50 p.m. the filament had risen only a little more, and it fell during the night. On the follow- ing morning the lobes were closing more quickly, and by 5 p.m. it was evident to the eye that they had closed considerably ; by 8.48 p.m. this was still plainer, and by 10.45 p.m. the marginal spikes were interlocked. ‘The leaf fell a little during the night, and next morning (25th) at 7 am. the lobes were completely shut. The course pursued, as may be seen in the figure, was