THE GYMNOSPERMS 95 
of pollen-grains from the stamen to the tip of the ovule is 
called pollination. Then the wall of the pollen-grain de- 
velops a tube, which pushes its ways through the ovule 
toward the egg. Meanwhile there have been developed 
either within the pollen-grain or the tube two male gam- 
etes, beside some other cells, and these are carried by the 
tube to the egg within the ovule. One male gamete fuses 
with the egg. From the oospore thus formed a young sporo- 
phyte begins to develop, and about the time it has developed 
the regions for the root, the stem, and the leaves, the walls 
of the ovule become hard, the embryo stops growing, and 
the whole structure now known as the seed passes into a 
resting-condition. It requires more than two years for the 
completion of a pine seed. After a period of rest, this seed, 
under favorable conditions, will develop a new pine plant. 
It is evident that the young pine plant is already in the seed, 
and needs only favorable conditions to begin to escape. 
Examine two-year-old cones. Remove sporophylls and 
note the seeds to which wings are attached. Sketch seed 
and wing. What is the wing for? Dissect the seed, note 
the heavy coatings, the abundant food material stored 
within it, and the straight embryo. Of the latter note the 
root, stem, and leaf regions. Draw. Plant a number of 
good seeds and see how the young plant comes up. See 
how many leaves (seeds leaves) it has when it first appears. 
How does the plant get free from the seed-coats? 
General questions.—Of what advantage is it to the pine 
to have its leaves narrow and so heavy-walled? Could they 
be protected so economically if they were very broad and 
thin? Does the structure of the leaf place any limitations 
on the rapidity of its growth? Of what advantage is it to 
have the cones so thoroughly sealed by the resinous matter? 
Do pines expose more chlorophyll to the light than do 
ferns? Which have better devices for the distribution of 
their young plants? 
