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TEXTBOOK OF BOTANY 



The form of a tree is also influenced by the angle at which 

 the branches grow out from the trunk. If they are nearly 

 horizontal like those of an oak, the tree has a broad crown ; 

 if they are nearly upright, as those of the Lombardy poplar 



-The swamp white oak (Qiiercus bicolor). Photograph by 

 R. H. Denniston and G. ICemmerer. 



are, the crown is narrow and cylindrical. Thus each species 

 has a crown of characteristic form, which is determined by the 

 factors that have been mentioned and by others, such as the 

 number of the branches and their stiff or drooping habit. 

 The same principles, of course, apply also to smaller plants 

 with erect branching stems. 



