Chap. I. TWINING PLANTS. 33 



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 Ijiomoea 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 some- 

 times 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 them- 

 selves, 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 Leguminosre, 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 Miiller * states that although Mihania 



* Journal of the Linn. Soc. interesting paper, in which he 

 ^Bot.) vol. ix. p. 314. I shall corrects or confirms various state- 

 have occasion often to quote this ments made by me. 



