STEMS 43 
it has developed into a great variety of forms or habits. 
In some trees, as the pines and their allies, the main stem 
continues as a central shaft to the top, the branches spread- 
Tia, 42.—An Austrian pine. 
ing horizontally from it (Fig. 42); while in other trees, as 
the oak and the elm (Figs. 43 and 44), the main stem 
soon divides into large branches. In the former case the 
