CLIMBING AND WATER PLANTS 107 



CHAPTER X 



SPECIAL FEATURES OF CLIMBING AND 

 WATER PLANTS 



THERE are several groups of plants in 

 which the stems are more or less exposed to 

 forces similar to those commonly affecting 

 the roots we have been considering. We find 

 that such stems often exhibit corresponding 

 deviations from the normal stem structure, 

 whereby they become enabled to withstand 

 these special directions of stress. 



One of the most interesting examples is 

 furnished by the great group of climbing 

 plants. The climbers have sprung from non- 

 climbing ancestors, in the different ranks 

 of the vegetable kingdom, but we here are 

 concerned only with those which belong to 

 the flowering plants. Many obvious points 

 of close similarity are shared by all climbers, 

 however distantly related they may be in 

 other respects. They usually possess rela- 

 tively thin main stems which are dependent 

 on other objects, bushes, trees and the like, 

 for their support. By growing to the tops 

 of the latter they are enabled to expose their 

 own abundant foliage freely to the light 

 without the economic disadvantages attendant 



