PLANTS OF THE CLOVER FAMILY. 89 



season in the green form varies from one to seven or 

 eight, but the average may be stated as four, and 

 the yield per cutting may be put at four to six tons 

 per acre. In areas not a few, therefore, from sixteen 

 to twenty- four tons of green alfalfa may be obtained 

 per acre from season to season, and with no other 

 labor after the crop has been established than that 

 of opening the sluices which let in the irrigating 

 waters. Nor are those alfalfa lands likely to become 

 exhausted soon, because of the extent of the subsoil 

 from which they draw food supplies. 



Distribution. But few plants are of wider dis- 

 tribution than alfalfa. While it is not able to endure 

 temperatures so low as some of the real clovers, it 

 will thrive in latitudes too warm and dry to produce 

 these kinds in good form. The growth of alfalfa 

 would seem to be more hedged in by conditions that 

 relate to soil and subsoil than by those which relate 

 to climate. Because of these limitations, alfalfa will 

 yield abundantly in certain areas within a state, and 

 in other areas in close proximity to them it cannot 

 be grown at all. It can probably be successfully 

 grown in portions of each state in the Union. So 

 wide is its distribution that it is successfully grown 

 in some portions of Quebec, Ontario and British 

 Columbia in Canada. 



But the distinctive alfalfa belt of the United 

 States lies west of the Mississippi and south o>f the 

 Missouri. It embraces nearly every Rocky moun- 

 tain valley from Canada to Mexico. It includes 

 areas possessed of subterranean waters, not too dis- 

 tant from the surface, as well as those which it may 

 be necessary to irrigate at certain seasons; also 



