v.] 



GERMINATION 



125 



in such a critical condition. The following table shows 

 the range of temperatures for the germination of various 

 cultivated plants. 



Temperatures of Germination. 



The practical bearing of these figures is obvious; 

 it is necessary to sow some seeds, like the melon, in 

 heat, and to defer the seeding of other crops, like 

 mangolds or maize, until the ground has acquired not 

 only the temperature necessary for germination but 

 one that will ensure a subsequent rapid growth of 

 the seedling plants. 



For example, turnips will germinate at almost as 

 low a temperature as barley, but the optimum tempera- 

 ture is higher for turnips ; they are therefore sown much 

 later in the spring, when the ground has more nearly 

 reached this temperature, because the seed is small and 

 the young plant very susceptible to insect attacks, so 

 that the turnip seed must germinate and grow away 

 rapidly if it is to succeed. 



Under ordinary field conditions much of the 

 nutrition of the crop depends upon the activity of 

 certain bacteria in the soil which break down organic 

 compounds containing nitrogen, and ultimately resolve 

 them into the nitrates taken up by the plant Most 



