SEED-BEARING PLANTS 415 
mutual shading and crowding, resulting in natural 
pruning, when trees grow close together in the forest. 
367. Long and Short Branches. The pines, like several 
other groups of plants, bear two distinct kinds of branches 
long branches, and short branches. The short branches 
are often called "spur-shoots." Long branches, in 
addition to being longer and larger, commonly bear 
only scale-like leaves, while the spur-shoots bear the 
foliage-leaves (Fig. 308). In certain cases juvenile forms 
of long branches are recognized, which bear foliage-leaves 
as an exception to the general rule. 
368. Leaves. The long, needle-like leaves of the pine 
are familiar to everyone. They occur on the spur-shoots 
in groups or fascicles of one, two, three, or five, according 
to the species. The spur-shoots are borne in the axils of 
the scale-like leaves of the long shoots (Fig. 307). The 
base of the leaf cluster is sheathed by the thin membranous 
scales of the terminal bud of the spur. When there are two 
leaves in a fascicle they are semi-circular in cross-section, 
the adjacent faces being flattened as a result of their 
contact in the bud; when there are three or more they 
are triangular in cross-section. The white pine (Pinus 
Strobus), and its nearest relatives, have five leaves to a 
fascicle, the pitch-pine (P. rigida), and its nearest relatives, 
bear the leaves in threes, the scrub-pines and the Euro- 
pean pine (P. sylvestris), in twos. 
369. Leaf -fall. The duration of the leaves varies with 
the species and the locality from two to ten years. As a 
result there are always green leaves on the tree, whence the 
term "evergreen." That the leaves are shed may be 
easily determined by examining the ground under any 
pine tree. The duration of the leaves is also easily 
