CHAPTER II 
CHARACTERISTICS, STRUCTURE, AND LIFE OF 
TREES 
=| HE woody plants, trees, shrubs, and some vines, 
te4| 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 differentiated 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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