SHOOTS 
67 
common trees may be known, even at a distance, by their 
characteristic habits (see Figs. 60, 61, 62). The difficulty 
of the mechanical problems solved by these huge bodies 
is very great. They maintain form and position and en- 
dure tremendous pressure and strain. 
FIG. 58. An elm in its winter condition, showing the absence of a continuous central 
shaft, the main stem soon breaking up into branches, and giving a spreading top. 
On each side in the background are trees of the pine type, showing the central 
shaft and conical outline. 
