第9章 TWINING PLANTS(8)

April 14, 1st circle was made in 32018, 2nd 25018, 3rd 25518, 4th 355 (late in afternoon)Adhadota cydonaefolia (Acanthaceae) follows the sun.A young shoot made a semicircle in 24 hrs.; subsequently it made a circle in between 40 hrs.and 48 hrs.Another shoot, however, made a circle in 26 hrs.30 m.

Mikania scandens (Compositae) moves against the sun.

H.M.

March 14, 1st circle was made in3 1015, 2nd 3016, 3rd 3017, 4th 3 33April 7, 5th 2 507, 6th 2 40 {This circle was made { after a copious water-{ ing with cold water at { 47 degrees Fahr.

Combretum argenteum (Combretaceae) moves against the sun.Kept in hothouse.

H.M.

{Early in morning, when Jan.24, 1st circle was made in255 { the temperature of the { house had fallen a { little.

24, 2 circles each at an }

average of }220

25, 4th circle was made in225Combretum purpureum revolves not quite so quickly as C.argenteum.

Loasa aurantiaca (Loasaceae).Revolutions variable in their course:

a plant which moved against the sun.

H. M.

June 20, 1st circle was made in 23720, 2nd21320, 3rd4021, 4th23522, 5th32623, 6th35Another plant which followed the sun in its revolutions.

H. M.

July 11, 1st circle was made in 151 }

11, 2nd146 } Very hot day.

11, 3rd141 }

11, 4th148 }

12, 5th235 }

Scyphanthus elegans (Loasaceae) follows the sun.

H. M.

June 13, 1st circle was made in 14513, 2nd11714, 3rd13614, 4th15914, 5th23Siphomeris or Lecontea (unnamed sp.) (Cinchonaceae) follows the sun.

H.M.

{(shoot extremely May 25, semicircle was made in 10 27 { young)26, 1st circle 10 15 (shoot still young)30, 2nd 8 55June 2, 3rd 8 116, 4th 68

{ Taken from the 8, 5th 7 20 { hothouse, and 9, 6th 8 36 { placed in a room { in my house.

Manettia bicolor (Cinchonaceae), young plant, follows the sun.

H.M.

July 7, 1st circle was made in 6188, 2nd 6539, 3rd 630Lonicera brachypoda (Caprifoliaceae) follows the sun, kept in a warm room in the house.

H. M.

April, 1st circle was made in910 (about){(a distinct shoot, very April, 2nd circle was made in 1220 { young, on same plant)3rd 730

{In this latter circle, { the semicircle from { the light took 5hrs.

4th 80 { 23 m., and to the { light 2 hrs.37min.:

{ difference 2 hrs 46m.

Aristolochia gigas (Aristolochiaceae) moves against the sun.

H. M.

July 22, 1st circle was made in80 (rather young shoot)23, 2nd71524, 3rd50 (about)In the foregoing Table, which includes twining plants belonging to widely different orders, we see that the rate at which growth travels or circulates round the axis (on which the revolving movement depends), differs much.As long as a plant remains under the same conditions, the rate is often remarkably uniform, as with the Hop, Mikania, Phaseolus, &c.The Scyphanthus made one revolution in 1 hr.

17 m., and this is the quickest rate observed by me; but we shall hereafter see a tendril-bearing Passiflora revolving more rapidly.Ashoot 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.; yet this latter plant is an efficient twiner.Species of the same genus move at different rates.The rate does not seem governed by the thickness of the shoots: those of the Sollya are as thin and flexible as string, but move more slowly than the thick and fleshy shoots of the Ruscus, which seem little fitted for movement of any kind.The shoots of the Wistaria, which become woody, move faster than those of the herbaceous Ipomoea or Thunbergia.

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

A greater number of twiners revolve in a course opposed to that of the sun, or to the hands of a watch, than in the reversed course, and, consequently, the majority, as is well known, ascend their supports from left to right.Occasionally, though rarely, plants of the same order twine in opposite directions, of which Mohl (p.125)gives a case in the Leguminosae, and we have in the table another in the Acanthaceae.I have seen no instance of two species of the same genus twining in opposite directions, and such cases must be rare;but Fritz Muller states that although Mikania scandens twines, as I have described, from left to right, another species in South Brazil twines in an opposite direction.It would have been an anomalous circumstance if no such cases had occurred, for different individuals of the same species, namely, of Solanum dulcamara (Dutrochet, tom.xix.p.299), revolve and twine in two directions: