evolving movement, and manner of ascent - Stems not irritable - Rate of revolution in various plants

that the surprising phenomenon of the spontaneous revolutions of the stems and tendrils of climbing plants had been long ago observed by Palm and by Hugo von Mohl, 3 and had subsequently been the subject of tw

clasp it; such organs consisting of modified leaves, branches, or flower-peduncles. But these two classes sometimes graduate to a certain extent into one another. Plants of the third class ascend merely by the aid of hooks

NG PL

next-formed, whilst very young, may be seen to bend to one side and to travel slowly round towards all points of the compass, moving, like the hands of a watch, with the sun. The movement very soon acquires its full ordinary velocity. From seven observations made during August on shoots proceeding from a plant which had been

volving movement. I will assume that it made at least one revolution during the first twenty-four hours. Early the next morning its position was marked, and it made a second revolution in 9 hrs.; during the latter part of this revolution it moved much quicker, and the third circle was performed in the evening in a little over 3 hrs. As on the succeeding morning I found that the shoot revolved in 2 hrs. 45 m., it must have made during the night four revolutions, each at the average rate of a little over 3 hrs. I should add that the temperature of the room varied only a little. The shoot had now grown 3.5 inches in length, and carried at i

a little. There was only one irregular movement, which consisted in the stem rapidly making, after an unusually slow revolution, only the segment of a circle. After the seventeenth revolution the internode had grown from 1.75 to 6 inches in length, and carried an internode 1.875 inch long, which was just perceptibly moving; and this carried a very minute ultimate internode. After the twenty-first revolution, the penultimate internode was 2.5 inches long, and probably revolved in a per

l revolving at the extremity, but of course no longer round the old central point of the supporting stick. From the changed position of the centre of gravity of the extremity, as it revolved, a slight and slow swaying movement was

lly, but slowly, swayed from side to side in a semicircular course, with the extreme internodes making complete revolutions. This swaying movement was certainly due to the movement of the lower internodes, which, however, had not 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 top to grow out almost horizontally to the length of 31 inches; this now consisted of three long internodes, terminated by two s

k point gradually turns round and sinks to the lower side, and comes up again when the circle is completed; and this gives the false appearance of twisting, which, in the case of spontaneously revolving plants, deceived me for a time. The appearance is the more deceitful because the axes of nearly all twining-plants are really twisted; and they are twisted in the same direction with the spontaneous revolving movement. To give an instance, the internode of th

best evidence, however, that the twisting does not cause the revolving movement is afforded by many leaf-climbing and tendril-bearing plants (as Pisum sativum, Echinocystis lobata, Bignonia capreolata, Eccremocarpus scaber, and with the leaf-climbers, Solanum jasminoides and various species of Clematis), of which the internodes are not twisted, but which, as we shall hereafter see, regularly perform revolving movements like those of true twining-plants. Moreover, according to Palm (pp. 30, 95) and Mohl

tems which had twined up the glass rods; for these rods were fixed into split sticks below, and were secured above to cross sticks, and the stems in passing these places became much twisted. As soon as the stems which had ascended the iron rods reached the summit and became free, they also became twisted; and this apparently occurred more quickly during windy than during calm weather. Several other facts could be given, showing that the axial twisting stands in some relation to inequalities in the support, and likewise to the shoot revolving freely without any support

namely, one twist for each spire completed. This was well shown by painting straight lines on living stems, and th

pt an inch or two of the extremity, be tied up, this part, as I have seen in the case of the Hop, Ceropegia, Convolvulus, &c., goes on revolving, but much more slowly; for the internodes, until they have grown to some little length, always move slowly. If we look to the one, two, or several internodes of a revolving shoot, they will be all seen to be more or less bowed, either during the whole or during a large part of each revolution. Now if a coloured streak be painted (this was done with a large number of twining plants) along, we will say, th

the lateral face; and when again bent to the south, the line will be on the original convex surface. Now, instead of bending the sapling, let us suppose that the cells along its northern surface from the base to the tip were to grow much more rapidly than on the three other sides, the whole shoot would then necessarily be bowed to the south; and let the longitudinal growing surface creep round the shoot, deserting by slow deg

ly, the summit would describe a simple arc; if the growth first travelled a very little to the western face, and during the return a very little to the eastern face, a narrow ellipse would be described; and the sapling would be straight as it passed to and fro through the intermediate space; and a complete straighteni

emma, Clerodendron, Wistaria, Stephania, Akebia, and Siphomeris, has exactly the same kind of movement as the other internodes; for a line painted on the convex surface first becomes lateral and then concave; but, owing to the youth of these terminal internodes, the reversal of the hook is a slower process than that of the revolving movement. 10 This strongly marked tendency in the young, terminal and flexible internodes, to bend in a greater degree or more abruptly than the other internodes, is of service to the plant; for not only does the hook thus formed sometimes serve to catch a support, but (and this seems to be much more important) it causes the extremity of the shoo

ion is necessarily arrested at the point of contact, but the free projecting part goes on revolving. As this continues, higher and higher points are brought into contact with the support and are arrested; and so onwards to the extremity; and thus the shoot winds round its support. When the shoot follows the sun in its revolving course, it winds round the support from right to left, the support being supposed to stand in front of the beholder; when the shoot revolves in an opposite dir

lk of any leaf climber, but without any effect. I then tied a light forked twig to a shoot of a Hop, a Ceropegia, Sphaerostemma, and Adhatoda, so that the fork pressed on one side alone of the shoot and revolved with it; I purposely selected some very slow revolvers, as it seemed most likely that these would profit most from possessing irritability; but in no case was any effect produced. 11 Moreover, when a shoot winds round a support, the winding movement is always slower, as we shall immediately see, than whilst it revolves freely and touches nothing. Hence I conclude tha

ency to be spiral; but when a shoot has nearly ceased to grow, or when the plant is unhealthy, the extremity does occasionally become spiral. I have seen this in a remarkable manner with the ends of the shoots of the Stauntonia and of the allied Akebia, which became wound up into a close spire, just like a tendril; and this was apt to

movement. The terminal internodes of a long, much-inclined, revolving shoot of the Ceropegia, after they had wound round a stick, always slipped up it, so as to render the spire more open than it was at first; and this was probably in part due to the force which caused the revolutions, being now almost freed from the constraint of gravity and allowed to act freely. With the Wistaria, on the other hand, a long horizontal shoot wound itself at first into a very close spire, which remained unchanged; but subsequen

sons visited a hop-field for me, and reported that though they generally found the points of insertion of the leaves standing over each other for a space of two or three feet in height, yet this never occurred up the whole length of the pole; the points of insertion forming, as might have been expected, an irregular spire. Any irregularity in the pole entirely destroyed the regularity of position of the leaves. From

ions coincide. This fact has been well shown by Dutrochet, 14 who found different individuals of Solanum dulcamara twining in opposite directions, and these had their leaves in each case spirally arranged in the sa

twining round a thin stick; showing that, although the power of movement was retained, this was not sufficient to enable the plant to twine. I then moved the stick to a greater distance, so that it was struck by a point 2.5 inches from the extremity of the penultimate internode; and it was then neatly encircled by this part of the penultimate and by the ultimate internode. After leaving the spirally wound shoot for eleven hours, I quietly withdrew the stick, and in the course of the day the curled portion straightened itself and recommenced revolving; but the lower

osite side. This movement of the shoot had a very odd appearance, as if 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, in which the growing surface was supposed to creep round from the northern by the western to the southern face; and thence back again by the eastern to the northern face, successively bowing the sapling in all directions. Now with the Ceropegia, the stick being placed to the south of the shoot and in contact with it, as soon as the circulatory growth reached the western surface, no effect would be produced, except that the shoot would be pressed firmly against the stick. But as soon as growt

ng revolving shoots of a Wistaria close to a post between 5 and 6 inches in diameter, but, though aided by me in many ways, they could not wind round it. This apparently was due to the flexure of the shoot, whilst winding round

n flexible, twine together into a cable, and thus support one another. Single thin depending shoots, such as those of the Sollya Drummondii, will turn abruptly backwards and wind up on themselves. The greater number of the depending shoots, however, of one twining plant, the Hibbertia dentata, showed but litt

, with a few appended remarks. These plants are arranged according to Lindley's 'Vegetable Kingdom' of 1853; and the

lution of variou

TYLE

(Polypodiaceae) mo

H

t circle was ma

6 15 (

5 32

5 0

5th

ulatum moves a

H

was made in 16 3

2nd

3rd

4th

COTYL

ae), placed in the hot-hou

H

was made in 6 1

2nd

3rd

4th

5th

6th

7th

m Kew) (Liliaceae) moves again

H

t circle was ma

2nd

ung shoot from a tuber in a pot plac

H

circle was mad

2nd

3rd

4th

5th

6th

esiaceae), in greenho

H

e was made in 26

micircle

d circle

3rd

4th

laced in the hothouse; but the next

ceae) moves against the sun; it co

TYLED

llows the sun. The plant was ke

H

ircles were made

3rd circle wa

4th

5th

6th

7th

8th

ng from the light, in 1 hr. 33 m.; in travelling to

laceae), placed in hothou

H

le was made in 4

2nd

3rd

4th

zabalaceae), placed in hoth

H

t circle was mad

2nd

ratum (Schizandrace

H

circle was made in

rcle was made i

(Menispermaceae) m

H

circle was mad

2nd

3rd

4th

e a circle in 12 hrs., and another in 10 hrs. 30 m.; but the next day, which

its course, and moved against the sun, and made a circle in 7 hrs.; on the 20th, moved against the sun one-third of a circle, and then stood sti

poraceae) moves against t

H

circle was made

8 0 (

3rd

4th

as I observed, no allied plant: follows the sun. Three shoots, cut off a plant,

uminosae), in greenhous

H

circle was mad

2nd

3rd

4th

5th

6th

uminosae), in greenhous

H

ircle was made

d

d

a (Apocynaceae) mov

H

t circle was mad

2nd

3rd

ssinoda moves

H

circle was mad

2nd

3rd

(Asclepiadaceae) m

H

in length 1st circle wa

young 2n

3rd

4th

5th

ves against the sun and made a circle in 6

made several circles in from

) moves against the sun. Plant p

emicircle, from the light in 1 hr. 14 m.,

emicircle, from the light in 1 hr. 17 m.,

ainst the sun, placed in my study, with w

circle, from the light in 4 hrs. 30 m., to t

circle, from the light in 3 hrs. 50 m., to the light 1 hr. circl

e power of light in retarding and hasten

against the sun. Two circles, were made each in 1 hr. 42

the sun, made four revolutions in 9 hrs.; so that

45 m. During the next few days it continued to move, but irregularly. On August 15th the shoot followed, during a period of 10 hrs. 40 m., a long and dee

moves against the sun. A circle was made in 7

sonii (Verbenacea

H

was made in 5 4

2nd

0 (directly after the p

d circle

4th

(Bignoniaceae) mo

H

t circle was mad

2nd

8 30

4th

(Acanthaceae) m

H

t circle was mad

2nd

3rd

3 55 (la

e a semicircle in 24 hrs.; subsequently it made a circle in between 40

(Compositae) move

H

t circle was mad

2nd

3rd

4th

5th

cle was made after a copious waterin

retaceae) moves against t

H

55 Early in morning, when the te

each at an avera

rcle was made

volves not quite so qu

lutions variable in their course:

H

circle was made

2nd

3rd

4th

5th

6th

h followed the sun

H

e was made in 1

2nd

3rd

4th

5th

ans (Loasaceae)

H

circle was made

2nd

3rd

4th

5th

(unnamed sp.) (Cincho

H

s made in 10 27

10 15

2nd

3rd

4th

Taken from the hothouse, and

6th

nchonaceae), young p

H

circle was mad

2nd

3rd

iaceae) follows the sun, kept

H

le was made in

n 12 20 (a distinct

d

semicircle from the light took 5 hrs. 23 m., and

Aristolochiaceae) mo

H

was made in 8 0

nd 7

5

by me; but we shall hereafter see a tendril-bearing Passiflora revolving more rapidly. A shoot of the Akebia quinata made a revolution in 1 hr. 30 m., and three revolutions at the average rate of 1 hr. 38 m.; a Convolvulus made two revolutions at the average of 1 hr. 42 m., and Phaseolus vulgaris three at the average of 1 hr. 57 m. On the other hand, some plants take 24 hrs. for a single revolution, and the Adhadota sometimes required 48 hrs.;

e plant may sometimes be seen revolving at different rates. The two or three, or even more, internodes which are first formed above the

species, namely, of Solanum dulcamara (Dutrochet, tom. xix. p. 299), revolve and twine in two directions: this plant, however; is a most feeble twiner. Loasa aurantiaca (Leon, p. 351) offers a much more curious case: I raised seventeen plants: of these eight revolved in opposition to the sun and ascended from left to right; five followed the sun and ascended from right to left; and four revolved and twined first in one direction, and then reversed their course, 17 the petioles of the opposite leaves affording a point d'appui for the reversal of the spire. One of these four plants made seven spiral turns from right to left, and five turns from left to right. Another plant in the same family, the Scyphanthus elegans, habitually twines in this same manner. I raised many plants of it, and the stems of all took one

emed as if constantly trying to ascend, but always failed. I then surrounded the plant with a mass of branched twigs; the shoots ascended, and passed through them, but several came out laterally, and their depending extremities seldom turned upwards as is usual with twining plants. Finally, I surrounded a second plant with many thin upright sticks, and placed it near the first one with twigs; and now both had got what they liked, for they twined up the parallel sticks, sometimes winding round one and sometimes round several; and

ea could not, when placed in a room with the light entering on one side, twine round sticks between 3 and 4 inches in diameter; for this interfered, in a manner presently to be explained, with the revolving movement. In the open air, however, the Phaseolus twined round a support of the above thickness, but failed in twining round one 9 inches in diameter. Nevertheless, some twiners of the warmer temperate regions can manage this latter degree of thickness; for I hear from Dr. Hooker that at Kew the Ruscus androgynus has ascended a column 9 inches in diameter; and although a Wistaria grown by me in a small pot tried in vain for weeks to get round a post between 5 and 6 inches in thickness, yet at

placed Ceropegia Gardnerii near a post 6 inches in diameter, but the shoots entirely failed to wind round it; their great length and power of movement merely aid them in finding a distant stem round which to twine. The Sphaerostemma marmoratum is a vigorous tropical t

al rate, taking quick and slow movers, amongst phanerogamic plants. The rate was accelerated by increased temperature. At each stage of growth only the two upper internodes revolved. A line painted along the convex surface of a revolving internode becomes first lateral, then concave, then lateral and ultimately again convex. Neither the internodes nor the petioles are irritable when rubbed. The movement is in the usual direction, namely, in opposition to the course of the sun; and when the stem twines round a thin sti

the movement for a time; hence I conclude that plants in a state of nature and growing in exposed situations, would not make their revolutions during very stormy weather. A decrease in temperature always caused a considerable retardation in the rate of revolution; but Dutrochet (tom. xvii. pp. 994, 996) has given such precise observations on this head with respect to the common pea that I need say nothing more. When twining plants are placed near a window in a room, 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 this differs in degree with different plants; thus Ipomoea jucunda made a complete circle in 5 hrs. 30 m.; the semicircle from the light taking 4 hrs. 80

ts of two kinds. With Periploca Graeca (Palm, p. 43) the uppermost shoots alone twine. Polygonum convolvulus twines only during the middle of the summer (Palm, p. 43, 94); and plants growing vigorously in the autumn show no inclination to climb. The majority of Asclepiadaceae are twiners; but Asclepias nigra only "in fertiliori solo incipit scandere subvolubili caule" (Willdenow, quoted and confirmed by Palm, p. 41). Asclepias vincetoxicum does not regularly twine, but occasionally does so (Palm, p. 42; Mohl, p. 112) when growing under certain conditions. So it is with two species of Ceropegia, as I hear from Prof. Harvey, for these plants in their native dry South African home generally grow erect, from 6 inches to 2 feet in height - a very few taller specimens showing some inclination to curve; but when cultivated near Dublin, they regularly twined up sticks 5 or 6 feet in height. Most Convolvulaceae are excellent twiners; but in South Africa Ipomoea argyraeoide

species of Solanum, and of another genus, viz. Habrothamnus, belonging to the same family, are described in horticultural works as twining plants, but they seem to possess this faculty in a very feeble degree. We may suspect that the species of these two genera have as yet only partially acquired the habit of twining. On the other hand with Tecoma radicans, a member of a family abounding with twiners and tendril-bearers, but which climbs, like the ivy, by the aid of rootlets, we may suspect that a former habit of twining has been lost, for the stem exhi