Sl'IHAL TWlNEItS. 19 



(Dicotyledons, continued.) 

 Lonicera brachypoda (Caprifoliacea) follows the sun, in a warn) room in 



the house. . 



h. in. 



April, 1st circle about 9 10 



„ 2nd ,, „ 12 20 (another shoot very young). 



„ 3rd „ „ 7 30 



{In this latter circle, the semicircle from the 

 light took 5 h. 23 in., and to the light 

 2 h. 37 m. : difference 2 h. 46 m. 



Arislolochia gigas (Aristolochiacere) moves against the sun. 



h. m. 

 July 22, 1st circle 8 (rather young shoot) . 



„ 23,2nd „ 7 15 



„ 24, 3rd „ 5 (about). 



In the foregoing table, which includes twining plants belonging 

 to as widely different orders as is possible, we see that the con- 

 traction or turgescence of the cells circulating round the axis, on 

 which the revolving movement depends, differs much in rate. As 

 long as a plant remains under the same conditions, the rate is 

 often remarkably uniform, as we see with the Hop, MiJcania, 

 Jfhaseolus, &c. The Scyphanthiis made one revolution in 1 h. 17m., 

 and this is the quickest rate observed ; but we shall afterwards 

 see a tendril-bearing Passiflora revolving even more rapidly. A 

 shoot of the Akebia quinata made a revolution in 1 b. 30m., and 

 three revolutions at the average rate of 1 h. 3S m.; a Convolvulus 

 made two revolutions at the average of 1 b. 42 m., and Phaseolus 

 vidt/aj'is three at the average of 1 h. 57m. On the other hand, some 

 plants take 21 h. for a single revolution, and the Adhadota some- 

 times required 48 h. ; 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 

 Solli/a are as thin and flexible as string, but move slower than the 

 thick and fleshy shoots of the liuscus, which seems so little fitted 

 for movement of any kind; the shoots of the Wistaria, which be- 

 come woody, move faster than those of the Ipomcea or Thuiibergia. 

 AVc know that the internodes, whilst very young, do not ac- 

 quire their proper rate of movement ; hence 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 perennial root-stock, do not 

 move ; these first-formed shoots can support themselves, and 

 nothing superfluous is granted them. 



A greater number of* twiners revolve in a course opposed to 

 that of the sun, or to the bauds of a watch, than in the reversed 



c2 



