2 TWINING PLANTS. Chap. I, 



I believe that my observations, founded on the ex- 

 amination of above a hundred widely distinct living 

 species, contain sufficient novelty to justify me in 

 publishing them. 



Climbing plants may be divided into four classes. 

 First, those which twine spirally round a support, and 

 are not aided by any other movement. Secondly, 

 those endowed with irritable organs, which when they 

 touch any object 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 ; and those of the 

 fourth by rootlets ; but as in neither class do the plants 

 exhibit any special movements, they present little 

 interest, and generally when I speak of climbing plants 

 I refer to the two first great classes. 



Twining Plants. 



This is the largest subdivision, and is apparently 

 the primordial and simplest condition of the class. 

 My observations will be best given by taking a few 

 special cases. When the shoot of a Hop (Humulus 

 lupulus) rises from the ground, the two or three first- 

 formed joints or internodes are straight and remain 

 stationary ; but the next-formed, whilst very young, 



apontanes/'&c./ComptesRendus,' ckerches sur la Volubilite des 

 torn. xvii. (1843) p. 989; "Re- Tiges,"<frc.,tom.xix.(1844)p.295. 



