THE SEED AND GERMINATION 49 
Maize has only one cotyledon, but much starchy 
endosperm. Cotyledon and outer layer of endosperm 
contain protein. 
Coconut is the inner part of a fruit. The flesh is 
the endosperm, and the germ is below the soft eye. 
The Date is a seed with hard cellulose endosperm. 
The germ is just below the surface at the back. 
A Seed is a young plant whose development has 
been arrested. 
Germination requires moisture, warmth, and 
oxygen, but not hght. 
Phenomena.—Seeds absorb water and exert great 
pressure, the radicle and plumule escape. Reserve 
materials become soluble. By diastase starch is 
changed into sugar, by cytase cellulose into sugar, and 
by lipase oil into fatty acids and glycerine. Carbon 
dioxide is produced by oxidation of the carbon com- 
pounds of the seed to supply energy. Heat is produced 
by this oxidation. 
Escape.—The plumule backs out of the cover. 
Where this is done by a loop formed above the coty- 
ledons the cotyledons are left in the earth (hypogean), 
where formed in the hypocotyl the cotyledons come 
above ground (epigean). In the onion and date the 
cotyledon tip remains for some time embedded in the 
endosperm. 
QUESTIONS ON CHAPTER II. 
1. To what kinds of plants are seeds essential? Explain 
why some plants might do without seeds. 
2. How are the delicate parts of a seed protected? 
3. Describe a sunflower seed and compare it with a castor- 
bean. 
4. Define hypocotyl, plumule, and seedling. 
5. Compare a monocotylous with a dicotylous seed. 
