6 MISC. PUBLICATION 162, U. S. DEPT. OF AGRICULTURE 
little separate films in the bark. In either case it dies from time to 
time, and is re-formed nearer the wood. 
Trees, like many other plants, bear flowers and reproduce by means 
of seed. When the tree enters on its long winter rest, it has its next 
year’s buds already formed. With the coming of spring, these buds 
expand and grow until they finally open into flowers or leaves. 
Some trees, as the elm and red maple, blossom and set fruit before 
the leaves open. The pussy willow and alder catkins burst forth 
before the frost is fairly out of the ground. Other trees wait until 
their leaves are partly grown before producing their blossoms, while 
still others, such as the chestnut and basswood, do not flower until 
early summer. 
Most of the cone-bearing trees, such as the pines, spruces, and firs, 
also blossom in the early spring. The staminate (male) and pistil- 
Figure 3.—An abundant seeding of yellowpoplar. 
Nature has to make a bounteous provision for the survival of her tree families, 
for only a small proportion of the seed scattered germinates. A still smaller 
proportion of the seedlings live to reach maturity. 
late (female) flowers are usually found on the same tree, and their 
color varies in the different species from yellow and orange to shades 
of pink, rose, or purple. The pines, especially, produce large quan- 
tities of pollen which is scattered by the wind. Geologically, the 
conifers are very old, being contemporary with the plant growth 
from which the coal deposits of today were formed. They still re- 
tain the simplicity of floral structure which marked the vegetation 
of those early times. 
Some trees mature their seeds rapidly and scatter them early in 
the growing season. This gives the seedlings a long summer for 
their first season’s growth. Others, such as the nut trees, slowly 
