WOODY PLANTS IN WINTER 



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.HE IDENTIFICATION of woody plants in winter has a 

 well-developed technique of its own which, while quite different 

 from the techniques used for the determination of the same plants 

 during the other seasons of the year, may be fully as reliable. 

 Most woody plants have an individuality of their own which is just 

 as evident in winter, at least upon careful examination, as it is 

 in summer. The morphological features used are, of course, not 

 usually those of flowers or fruits, or even of leaves, but the size 

 and form of the plants and especially the structures of the younger 

 branches, or twigs. 



Size and Form of Woody Plants . The sizes of woody plants 

 are, of course, quite variable, but an effort is made, in the de- 

 scriptions of the following pages, to give the general range of the 

 height (and for trees, especially, the trunk diameter) of mature 

 plants. It is realized that trees, when young, are no taller than 

 shrubs, and it may be difficult in winter to tell if a given plant 

 has reached maturity or not, but the figures would be meaningless 

 otherwise. 



Trees and shrubs grown in the open tend to have a character- 

 istic form well illustrated by such species as white pine, Lombardy 

 poplar, weeping willow, and American elm. In general, however, 

 under forest conditions the crown is restricted in its development 

 by the competition of surrounding trees and the form is not so dis- 

 tinctive. 



Bark. Bark , or periderm, is that portion of a woody stem 

 which lies outside of the cambium layer, and is protective in na- 

 ture. The very youngest stems are covered by epidermis, but this 

 is usually quickly succeeded by periderm, having its origin in 

 superficial layers of the cortex. Compared with older bark, this 

 is quite smooth, broken only by lenticels. At this stage, color is 

 an important feature for diagnostic purposes. On older branches 

 or trunks cork cambium (Fig. 1) originates deeper in the stem and 

 when these deeper layers are formed the tissues on the outside die 

 and the bark tends to become scaly or furrowed (Fig. 4), often 

 according a very distinctive pattern. In sour gum, flowering dog- 

 wood, and persimmon, for example, the bark is divided into small 



