HISTORY AND EVOLUTION 25 



Many soils that have been cultivated for 

 a long time are acid, and therefore not 

 adapted for growing leguminous plants 

 such as clover or sweet peas even though 

 the soil may be fertile. The lime corrects 

 this condition, and also releases plant food 

 which otherwise would not soon become 

 available. Clay soils are made more open 

 and porous by the action of lime. 



Planting 

 The Seed. Some primrose and white- 

 flowered varieties have white or light-col- 

 ored seeds, and some have black seeds. 

 The white seeds often rot in the soil, espe- 

 cially if they are planted early when the 

 soil is cold, or because their germinating 

 power has been impaired; also they fre- 

 quently split in the pod before harvesting 

 and in this condition are likely soon to lose 

 their vitality. For the foregoing reasons 



