SEEDS AND SEEDLINGS 31 
function of real leaves. They remain quite thick, however, and differ 
in that respect from the other leaves. In the morning glory the cotyle- 
dons are as thin as other leaves. 
8. The pea comes out of the ground with the end arched over. This 
serves the purpose of protecting the delicate growing tip by making it 
unnecessary for it to keep at the front as it pushes its way through the 
earth. The cotyledons remain stationary in the ground because the 
caulicle does not elongate and push them upward. The roots spring 
directly from the short caulicle and only the plumule grows upward. 
g. The growth of the germ in the kernel of corn is quite different 
from the cases we have studied. The seed remains underground and 
gives nourishment to the growing plantlet, which gradually absorbs it 
and leaves the husk of the kernel empty. Corn has but one cotyledon, 
and that remains inclosed in the grain. The plumule is erect, instead of 
arched, as it emerges from the ground. Wheat, oats, barley, and other 
species of the grass family come up in the same manner as corn. 
to. The reason why seeds will not germinate when they have too 
much moisture is because they require air for the process, and if they 
are covered with water, or with soil that is saturated with water, the air 
cannot get to them. Seeds of some plants, as rice, can germinate under 
water by using the air within them and by absorbing air from the water. 
11. This experiment will be very instructive as demonstrating the 
effect of a dry season upon seeds after planting. Of course, if the drought 
comes before the seeds have begun to sprout, no harm will be done 
except to delay their germination till they get moisture; but after they 
have begun to sprout drought will injure them. Vary the experiment 
in several ways and learn what is the nature and extent of the injury 
wrought by different degrees of dryness and at different stages of growth. 
You will find that sometimes the drought merely retards the growth, or 
perhaps kills a portion of the germinating seeds; under other conditions 
it may kill all. 
12. It is intended that there shall be moisture enough in the earth 
to sprout the seeds in both pots, but if no water is supplied to one lot 
some of the young plants will lose their vitality before they reach the 
surface, while the rest will have their growth retarded, and finally they 
also will die. As soon as all the plants appear to be dead, dump the 
earth out and see how dry it is. 
