PLANTS OF THE CLOVER FAMILY. 71 



least 50 per cent by judicious cultivation. The 

 yield from each of the other varieties is somewhat 

 g-reater than that obtained from the iirst cutting 

 of the medium clover, but it is likewise some- 

 what less than that obtained from the two cut- 

 tings of the latter. 



Distrihutioii. — The clover zone in the United 

 States and Canada covers the entire portion of the 

 arable land. But there are stretches of country, 

 nevertheless, in which clover of any of the species 

 heretofore introduced has not been grown with any 

 marked success. One of these stretches lies east of 

 the Rocky mountains in what is usually spoken of 

 as the semi-arid belt. In this area it perishes from 

 want of moisture. Another stretch lies to the north 

 of Minnesota and North Dakota, where the low 

 winter temperatures forbid the successful growth of 

 clover. In some limited areas of these stretches, 

 some kinds of clover can be grown, but it cannot be 

 said of the same that they have high adaptation for 

 growing clover, nor can any of the clovers now 

 under discussion be grown with marked success in 

 the southern states, unless it be the crimson. The 

 summer heat is not favorable to its development. 



The distribution of the medium, mammoth and 

 alsike species of clover is about the same, but the 

 alsike can be grown somewhat farther north than the 

 medium or the mammoth. Above the 50th parallel 

 these clovers are not a success, nor are they a marked 

 success below the 38th parallel, unless in very limited 

 areas. In much of the country between these 

 parallels they can be grown with more or less suc- 

 cess, save in the semi-arid country beside the Rocky 



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