312 HOW CROPS GEOW. 



The endosperm, if the seed have one, and in many cases 

 the cotyledons (so with the horse-bean, pea, maize, and 

 barley), remain in the place -where the seed was deposited. 

 In other cases (kidney-bean, buckwheat, squash, radish, 

 etc.,) the cotyledons ascend and become the first pair of 

 leaves. 



The ascending plumule shortly unfolds new leaves, and 

 if coming from the seed of a branched plant, lateral buds 

 make their appearance. The radicle divides and subdi- 

 vides in beginning the issue of true roots. 



When the plantlet ceases to derive nourishment from 

 the mother seed, the process is finished. 



THE CONDITIONS OF GERMINATION. 



As to the Conditions of Germination we have to con- 

 sider in detail the following : — 



a< Temperature • — A certain range of warmth is essen- 

 tial to the sprouting of a seed. — Goppert, who experiment- 

 ed with numerous seeds, observed none to germinate be- 

 low 39°. 



Sachs has ascertained for various agricultural seeds the 

 extreme limits of warmth at which germination is possi- 

 ble. The lowest temperatures range from 41° to 55°, the 

 highest, from 102° to 116°. Below the minimum temper- 

 ature a seed preserves its vitality, above the maximum it 

 is killed. He finds, likewise, that the point at which the 

 most rapid germination occurs is intermediate between 

 these two extremes, and lies between 79° and 93°. Either 

 elevation or reduction of temperature from these degrees 

 retards the act of sprouting. 



In the following table are given the special tempera- 

 tures for six common plants. 



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