70 



PLANT KELATIONS. 



Fig. 61. Cottonwoods, in winter condition, on a sand dune, showing the branching 

 habit, and the tendency to grow in groups. 



grows towards the light, while floating stems may be 

 either erect or transverse. 



B. Stems bearing scale leaves. 



40. General character. — A scale leaf is one which does 

 not serve as foliage, as it does not develop the necessary 

 chlorophyll. This means that it does not need such an 

 exposure of surface, and hence scale leaves are usually much 

 smaller, and certainly are more inconspicuous than foliage 

 leaves. A good illustration of scale leaves is furnished by 

 the ordinary scaly buds of trees, in which the covering of 

 overlapping scaly leaves is very conspicuous (see Fig. 65). 

 As there is no development of chlorophyll in such leaves, 



