14: 



The Gakden. 



inefficacious; and so are moisture and warmth in the absence of 

 the oxygen ; for seeds will not germinate in a vacuum, nor in 

 distilled or recently boiled water. 



Moisture is necessary to soften and expand the various parts, 

 to dissolve soluble matter, and to establish a sort of circulation. 

 The embryo seems also to have the power of decomposing 

 water; and it is probable that a portion of the oxygen required 

 is obtained in this way. The rest must come from the air ; for 

 it is found that a communication with the atmosphere is abso- 

 lutely essential to perfect germination. The effect of heat ap- 

 pears to be to set the vital principle in action, to expand the 

 air in the numerous microscopic cavities of the seed, and to 

 produce distension of all the organic parts. The degree of 

 heat required varies with different species. The common 

 chickweed will germinate at a temperature but little above the 

 freezing-point, while the seeds of many tropical plants require 

 a heat of from 90° to 110° (Fahrenheit) to call them into 

 action. "Wheat, rye, and barley will germinate at 44°. A 



degree of heat vary- 

 ing from 113° to 

 167° is capable of 

 destroying the vital- 

 ity of the various 

 grains, beans, peas, 

 etc. Direct light, 

 so essential to sub- 

 sequent vegetation, 

 is unfavorable to 

 germination. 



The time required 

 for germination is 

 very different in dif- 

 ferent species of 

 plants. Much also 

 depends upon soil, 



TOUUO RADTSn, SUOV/INQ SEKD-LEAVB3. CUmatC, dCgrCO 01 



