134 THE PRINCIPLES OP AGRICULTURE 



219. The ideal condition of the seed-bed, so 

 far as water is concerned, is that it shall be 

 moist, not wet. Wet soil injures seeds, largely 

 by excluding oxygen. The older and weaker the 

 seeds, the greater is the necessity for care in 

 applying water : they should be kept only 

 slightly moist until germination is well started. 

 The soaking of seeds starts the germinating pro- 

 cesses, but it should not be continued above 

 twenty- four hours, as a rule, and should not 

 be employed with very weak seeds. 



220. Oxygen is supplied to germinating seeds 

 if sufficient air is allowed to reach them ; and 

 the air reaches them if they are not planted too 

 deep, nor kept too wet, nor the soil allowed to 

 ''bake." But all these conditions are greatly 

 modified by the kind of soil. 



221. For each kind of seed there is a certain 

 degree of warmth under which it will germinate 

 to the best advantage ; and this is called the 

 optimum temperature for that seed. The opti- 

 mum temperature is not uniform or exact, but 

 ranges through a limit of five to ten degrees. 

 ^ eds of most hardy plants — as wheat, oats, rye, 

 lettuce, cabbage, and wild plants — germinate best 

 in temperatures between 45° and 65°; those of 

 tender vegetables and conservatory plants, be- 

 tween 60° and 80°; those of tropical plants, 

 between 75° and 95°. 



