CHAPTER II 



CHARACTERISTICS, STRUCTURE, AND LIFE OF 



TREES 



HE woody plants, trees, shrubs, and some vines, 

 differ from all other plants in at least two 

 directions: namely, in their persistent life, 

 with only temporary rest periods in growth, — 

 a characteristic which indicates differences in structure from 

 that of annuals — and in their elevation in height above 

 the rest of vegetation, which implies, besides difference in 

 structure, difference in performing the functions of life. 



Trees as a rule show these two characteristics of height and 

 persistency of life in a most pronounced degree. In addi- 

 tion, they differ from shrubs and vines by their form; namely, 

 a single stem, rising from the ground, — the bole or trunk, 

 — which develops more strongly than the branches, into 

 which it divides in characteristic fashion, and which in their 

 aggregate may be dift'erendated as the crown. These char- 

 acteristics of form, longevity, and height make trees the 

 most prominent and one of the most important, and most 

 interesting features in the living vegetable world. 



To be able to care for trees, to diagnose diseases or abnor- 

 mal conditions and to apply remedies judiciously, it is neces- 

 sary to know and understand something of the structure, 

 and of the life requirements of a healthy tree in normal 

 condition. Indeed, we may say that only to the extent 

 that this primary knowledge is possessed, can a rational 

 treatment of trees be expected. 



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