48 THE GERMINATION OF SEEDS. 



CHAPTER III. 

 PLANT GROWTH. 



Germination of Seeds. Figures 56, 57, 58, on a former 

 page, illustrate the parts of a kernel of corn and its mode of 

 growth. Tor the account of the structure of the seed consult a 

 former paragraph on this subject. It will be seen that the grain 

 of corn, as is true of all the grasses, remains stationary where 

 planted, at the base of the ascending axis. 



( ' For germination to take place, moisture, oxygen and a suit- 

 able temperature are necessary. Under these conditions the 

 seed swells, oxygen is absorbed, a part of the carbonaceous 

 ingredients is oxidized, heat is developed, and carbon dioxide is 

 evolved. During these changes the solid ingredients of the seed 

 gradually become soluble ; the starch and fat are converted into 

 sugar; the albuminoids are converted into amides." (Waring- 

 ton's Chemistry of the Farm.) 



In the Temperate Zones, the seeds of grasses germinate quickly 

 at a rather low temperature, though there is considerable differ- 

 ence in this particular. Some germinate a little above the 

 freezing point, while every farmer knows that Indian corn, sor- 

 ghum and millet start slowly, unless the weather be quite warm, 

 and that the seeds will decay if kept wet and cold. 



Old or light seeds often sprout quickly, but produce weak 

 plants. 



Though the seeds of grasses be secured when quite young, in 

 the milk, a short time after flowering, when the endosperm is 

 very small and the seeds shrivel as they dry, yet, if the embryo 

 be formed and the seed well cured in a dry place, it will germi- 

 nate. Dry seeds will endure much cold ; wet or green seeds will 

 endure but little. 



Grass seeds may be covered deeper in a sandy soil than in clay, 

 deeper in a rather dry soil than in a wet one. 



