80 ALFALFA FARMING IN AMERICA. 



that it will succeed on sandy soil which is too light to produce 

 profitable crops of other forage plants. 



Yellow trefoil or Hop clover (Medicago lupulina L.) is an 

 annual species and may be distinguished from aifaifa by its more 

 spreading habit, its shorter and broader tipped leaves, by its yel- 

 low flowers, and, finally, by the fact that the pods are not coiled, 

 as with alfalfa, although coiled to make a single incomplete spiral. 

 These pods also differ from those of alfalfa in being black when 

 ripe. This species has some value in moist regions, but is far 

 inferior to alfalfa. 



Bur clover (Medicago denticulata Willd.) and Spotted Medic 

 ' (Medicago arabica All.), like yellow trefoil, are also annual 

 plants and have yellow flowers. They differ, however, from' all 

 of the above-mentioned species in having burry pods. Although 

 grown in some localities, they are of little agricultural conse- 

 quence. 



Bur clover inoculates land for alfalfa growing 

 or vice versa. They carry the same bacteria on their 

 roots. Mellilotus, or sweet clover, also uses the same 

 bacteria. This fact is useful since it often enables 

 us to get hold of inoculated soil, or to sow one of 

 the inferior clovers as a forerunner of alfalfa for 

 the purpose of inoculating the soil or of enriching it 

 and storing it with humus. 



Types and Varieties. — Alfalfa is remarkably vari- 

 able. One can go into a field sown all of one sort of 

 seed and select in it a hundred plants, no two having 

 very close likeness. Much can be done and will be 

 done to select varieties having desirable character- 

 istics. Already the Colorado and Kansas experi- 

 ment stations are doing considerable in this line, 

 while other stations not so well located are also at 

 work, notably Ohio, Minnesota and North Dakota, 

 and the Department of Agriculture at "Washington. 



Natural selection, -or the law of the survival of the 

 fittest, has done much to create types. For example, 



