SPIKAL TWINEES, 19 



(Dicotyledons, continued.) 



Loiiieera hrachy^poda (Caprifoliaccse) follows the sun, in a warm room in 

 the house. 



h. m, 



April, 1st circle about 9 10 



5, 2nd „ „ 12 20 (another shoot very young), 



„ 3rd „ „ 7 30 



In this latter cii'cle, the semicircle from the 



„ 4th „ „ 8 0^ light took 5h. 23m., and to the light 



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



AristolocJiia gigas (Aristolochiaceee) moyes against the sun. 



h, ni. 



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



„ 23,2nd „ ......... 7 15 



„ 24, 3rd „ 6 (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 muchiii rate. As 

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

 often remarkably uniform, as we see with the Hop, Mika/niUj 

 Fhaseolus^ &c. The ScypTianthus 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 AJcehia quinata made a revolution in 1 h. 30 m., and 

 three revolutions at the average rate of 1 h. 38 m.; a Convolvulus 

 made two revolutions at the average of 1 h. 42 m., and Fhaseolus 

 vulgaris three at the average of Ih. 57m. On the other hand, some 

 plants take 24 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 

 Sollya are as thin and flexible as string, but move slower than the 

 thick and fleshy shoots of the Huseu^, 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 Ipomcsa or Thunhergia, 

 AVe know that the intemodes, 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, intemodes 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 hands of a watch, than in the reversed 



c2 



y 



