GERMINATION 57 



stored in the endosperm. The food so absorbed, together with that 

 stored in the scutellum, passes over a sort of bridge to the sprouting 

 plumule and radicle. 



(4) It aids in the chemical and biological changes. The two 

 classes of food materials present in the largest amounts in the mature 

 seeds are the albuminoids and carbohydrates. The albuminoids in 

 cereals appear in aleurone grains. Starch represents the larger part 

 of the carbohydrates. The aleurone cells are thought to secrete 

 diastatic ferments. These ferments or "enzymes" begin immediately 

 to corrode the starch cells lying beneath. The epithelium of the scut- 

 ellum has similar secretive cells which become active very early. The 

 resultant product after the diastatic action on the starch is an invert 

 sugar which is readily soluble in water and is quickly absorbed by the 

 growing plant. Some soluble cane sugar enters the embryo as food 

 also. 



In the spoiling of stored grain the same process occurs. Bacteria, 

 yeasts, and moulds, which are universally present, change the sugars 

 to alcohol and acids, making the grain sour. In the case of the ger- 

 minating plant in the field, the sugar is used before the latter steps 

 have time to take place. 



PROPER TEMPERATURE. Many experiments have been made 

 with the seeds of cereals and grasses to determine the effect of heat 

 upon germination. The highest temperature at which a certain kind 

 of seed will germinate is termed the "maximum." The "minimum" 

 temperature refers to the lowest point at which the seed will ger- 

 minate. The most favorable temperature — the degree of heat which 

 produces the most rapid substantial growth — is the "optimum" tem- 

 perature. 



The following are the maximum, optimum, and minimum temper- 

 atures as given by Sachs for some of our most common farm seeds : 



Minimum. Optimum. Maximum. 



Wheat 41 84 104 



Barley 41 84 104 



Maize 48 93 "5 



Professor Gerald McCarthy, of the North Carolina Experiment 

 Station, gives: 



Minimum. Optimum. Maximum. 



Oats 55 70 90 



Rye 55 75 90 



