140 



PEACTICAL BOTANY 

 GERMINATION TEMPERATURES 



Most farmers have learned by experience that the tempera- 

 ture requirements of all kinds of seeds are not the same. All 

 know, for example, that if corn is planted before the ground is 

 warm enough, it Avill decay and have to be replanted, but that 

 peas can be sown very soon after the frost is out of the ground. 



There is moisture enough in a few kinds of seeds, like those 

 of the willow and the poplar, to allow them to begin to germi- 

 nate as soon as they are ripe. But most seeds need to be sup- 

 plied with moisture from without. Too little moisture causes 

 them to germinate very slowly, as is often noticed during 

 spring droughts, while immersing them in water causes many 

 kinds to rot because the air supply is not sufficient. 



Lack of air as a hindrance to germination is particularly 

 likely to occur when seeds are planted too deep in clay soils. 

 In warm, open soils there is usually air enough, and the dan- 

 ger encountered is that of drying up, from shallow planting. 



131. Preparation of seeds for germination. A few kinds of 

 seeds, as above mentioned, may sprout as soon as the}' are ripe. 

 Most sorts, however, need a period of rest and comparati\e 

 dryness before they will grow. The importance of drying 

 seeds is well shown in the case of corn. Kiln-dried corn has, 

 in one instance, been shown to yield 16 bushels per acre more 

 than air-dried seed of the same variety. 



