STEMS 69 
from adventitious or dormant buds on the trunk or limbs. 
Such spines sometimes show their true nature as branches 
by bearing leaves (Fig. 34). 
84. Indefinite Annual Growth. —In most of the forest 
trees, and in the larger shrubs, the wood of young branches 
is matured and fully 
developed during the 
summer. Protected 
buds are formed on 
the twigs of these 
branches to their very 
tips. In other shrubs 
— for example, in the 
sumac, the raspberry, 
and blackberry — the 
shoots continue to 
grow until their soft \ 
and immature tips are Fic. 34.—Leaf-Bearing spine \\\ |= 
killed by the frost. ae 2 ieee \ 
Such a mode of growth is called indefinite 
annual growth, to distinguish it from the 
definite annual growth of most trees. 
85. Trees, Shrubs, and Herbs. — Plants 
of the largest size with a main trunk of a 
woody structure are called trees. Shrubs 
differ from trees in their smaller size, and ~ 
generally in having several stems which proceed from the 
ground or near it or in having much-forked stems. The 
witch-hazel, the dogwoods, and the alders, for instance, 
are most of them classed as shrubs for this reason, though 
in height some of them equal the smaller trees. Some of 
‘ 
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