THE SEED AND ITS GERMINATION 7 
part of the embryo. This is really the single cotyledon of the 
corn (Fig. 6). It does not as a whéle rise above ground, but most 
of it remains in the buried grain and acts as a digesting and absorb- 
ing organ through which the endosperm or food stored outside of the 
embryo is transferred into the growing plant as fast as it can be 
made liquid for that purpose. 
5. Conditions Requisite for Germination. — When we try 
to enumerate the external conditions which may affect 
germination, we find that the principal ones are heat, 
moisture, and presence of air. A few simple experi- 
ments will show what influence some of these condi- 
tions exert. 
6. Temperature. — Common observation shows that a 
moderate amount of warmth is necessary for the sprouting 
of seeds. Every farmer or gardener knows that during a 
cold spring many seeds, if planted, will rot in the ground. 
But a somewhat exact experiment is necessary to show 
what is the best temperature for seeds to grow in, and 
whether variations in the. temperature make more differ- 
ence in the quickness with which they begin to germinate 
or in the total per cent which finally succeed. 
EXPERIMENT I 
Relation of Temperature to Germination. — Prepare at least four 
teacups or tumblers, each with wet soft paper packed in the bottom 
to a depth of nearly an inch. Have a tightly fitting cover over 
each. Put in each vessel the same number of soaked peas. Stand 
the vessels with their contents in places where they will be exposed 
to different, but fairly constant, temperatures, and observe the sey- 
eral temperatures carefully with a thermometer. Take pains to 
keep the tumblers in the warm places from drying out, so that their 
contents will not be less moist than that of the others. The following 
