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 iduring the \ 



summer. Protected "~^\ 



buds are formed on \v 



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 



killed by the frost. 



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 ar^ called trees. Shrubs 

 differ from trees in their smaller size, and 



generally in having several stems which proceed from the 

 ground of 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. Sonie of 



'Fig. 34. — Leaf-Bearing Spine 

 of Honey Locust. 



