46 CLIMBING PLANTS [CHAP. 



climbing power in stems is easily forthcoming. 

 John Hunter, the eminent surgeon, thus wrote 

 in 1833 i 1 



"A bean, which when strong, seems to 

 depend entirely upon its own powers ; yet if 

 it grows weakly, as when not in the sun, or 

 any other cause acting to hinder strength when 

 growing in such, if a stick is put into the 

 ground close to it, it will twine round it in 

 loose spiral turns." 



This experiment I have imitated with the 

 periwinkle. This plant makes long summer 

 shoots which, like those of the blackberry, 

 bend downwards by their weight till they touch 

 the ground, and then strike root ; but they do 

 not climb. Growing a plant in darkness and 

 placing slender sticks close to the growing 

 shoots, they also made " loose spiral turns " 

 round the sticks (fig. 13). We here see, as 

 in everything else, a rapid response to new 

 environmental conditions. Still the question 

 remains : Is the effect hereditary ? The power 

 to climb is certainly hereditary, for if this be 

 originally acquired in deep shade or total dark- 

 ness, as in the experiment, it is now available 

 when the shoots or stems are green and in 

 sunlight, as in the convolvulus, etc. And this 

 power now inherited was acquired by twiners 

 or stem - climbers solely on the soma, long 

 before the reproductive organs were developed. 



1 " Memoranda of Vegetation/' p. 7. 



