136 From Matter to Man. 



functions or attributes in simple flowerless or flowering 

 plants, is not to be denied. 



In this evolution of vegetal mechanism and function, 

 the higher classes of climbing plants may or may not 

 be evolved from the same parent types as the lower. 

 Each species could quite independently evolve the 

 climbing habit, even although it was absent in the 

 parental type. Varying conditions, for instance, 

 could by natural selection gradually evolve modifica- 

 tions in the structures of different species of plants 

 which would be quite able to effect that special 

 purpose. Thus, all the climbing organs in vegetals 

 are but modifications of normal organs. The rootlets 

 are but modified roots, and the hooks and spines but 

 metamorphosed leaves ; the tendrils of the passion- 

 flower are a whole branch transformed ; those of the 

 vine, a flower peduncle ; those of the ordinary pea, a 

 modification of certain of the leaflets ; those of the 

 sweet-pea, the whole blade of the leaf; and those of 

 the sarsaparilla and cucumber, simply an alteration in 

 the stipules. Lastly, the common grape-vine displays 

 the whole series of gradations between the ordinary 

 flower-stalks and the tendrils of the vine, while the 

 berberry shows all the gradations between a leaf and 

 a spine. 



Many plants, such as the whin, gorse, or furze, 

 modify their foliar organs into spines and prickles, 

 although non-climbers. We thus see that as variation 

 and modification of organs happen accidentally in all 

 plants, climbing plants need not be correlated, much 



