Peas and Clover 157 
most of the Clovers it remains round the seed-vessel 
till this is ripe. 
The roots of the Clovers bear many nodules pro- 
duced by the nitrifying organisms, so that a field that 
has been cropped with Clover is rich in nitrogen, and 
farmers find it is particularly advantageous to follow 
Clover with a crop of wheat. 
