CLOVERS. 217 



5. The organic matter which is left in the soil also 

 improves the mechanical condition of most soils. 

 There are soils which contain all the fertilizing in- 

 gredients necessary to a fertile soil, but which do not 

 produce because of their mechanical or physical con- 

 dition. Probably the most important single physical 

 property is that with reference to the retention and 

 passage of water in the soil. The decay of vegeta- 

 ble matter modifies this property to a considerable 

 extent. 



Varieties. — The true clovers (Trifolium), includ- 

 ing possibly one or two other similarly growing plants, 

 are more important agriculturally in this country than 

 the large number of other valuable plants of the clover 

 family, because they are adapted to general and profit- 

 able culture over a wide range of territory. A brief 

 description of the more important is given. 



Red Clover {TrifoUum pratense, L.) is also 

 known as broad clover, broad leaved clover, com- 

 mon clover and meadow trefoil, and also as medium 

 red clover, to distinguish it from mammoth red clover. . 



It was one of the earliest forage plants to be 

 brought into systematic cultivation, having been in- 

 troduced into England in 1633 or about half a century 

 before perennial rye grass. 



Red clover is a plant of temperate climate. It is 

 widely diffused through Europe. It is successfnlly 

 cultivated throughout the United States ecist of the 

 one hundredth meridian and north of the Gulf states. 

 In this region it is cultivated for hay almost to the 

 exclusion of the other clovers and similar forage 

 plants. Where it is grown successfully it is not re- 

 placed by any other clover or similar plants, unless, 



