The Story-Book of the Fields 



at the other, and the little plant is now 

 subject to the influence of the earth and the 

 air. The germ takes more or less time to 

 free itself, according to the degree of resist- 

 ance of the seed-walls. If it is enclosed in a 

 compact kernel it takes a long time to become 

 saturated with moisture, and capable of 

 bursting its cell. For this reason the shells 

 of very hard seeds are rubbed away on a stone. 



Besides this mechanical part played by 

 water in causing the seeds to open, there is 

 another which relates to nutrition. The 

 changes by means of which the food materials 

 of the perisperm and cotyledons are liquefied 

 and become capable of absorption, can only 

 take place through water. Besides this fluid 

 is indispensable for dissolving the food sub- 

 stances, introducing them into the young 

 plant, and distributing them equally through- 

 out. So it will be seen that as long as it 

 remains dr} r it is impossible for any seed to 

 germinate, and if we wish to preserve seeds, 

 the first thing necessary is to keep them free 

 from damp. 



Warmth is necessary as well as water. 

 Generally speaking, germination is most suc- 

 cessful at a temperature of fifty-five to 

 seventy degrees — that of our spring and 



244 



