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 
