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 whole 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, 

 moistui'e, 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 sev- 

 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 



