No. 570] 



ALFALFA BREEDING 



361 



Morphologically the Mediterranean and Peruvian al- 

 falfas are so distinct in type that any one at all familiar 

 with the different kinds of alfalfa would recognize them 

 at a glance, whether a whole field or a single plant be 

 observed. The presence of yellow or greenish blue flow- 

 ers also determines a variety to be of northern origin with 

 mixtures of falcata characters, which usually carry with 

 them resistance to cold and drought. Otherwise, the 

 Turkestan, American and European types are so nearly 

 alike that only an expert would recognize them in mass 

 culture. The individual variations within these three 

 types intergrade to such a degree that one could scarcely 

 assume to judge, from the observation of a single plant, 

 the type prevailing in the field from which it originated. 

 The three types, however, differ markedly in their phys- 

 iological reactions as we shall presently see. The distinc- 

 tions, in this regard, as exhibited on our plots, are not 

 nearly so marked between the American and Turkestan 

 alfalfas as between these two types, on the one hand, and 

 the European, on the other. However, in northern cli- 

 mates where winter resistance enters as a potent factor, 

 the Turkestan alfalfa exhibits greater hardiness than the 

 American form, and, therefore, is able to maintain a more 

 perfect stand through seasons of extreme frost. 



When grown under Arizona conditions, the average 

 yields of each of these five type groups present seasonal 

 curves at once striking in their diversity and contrasts. 

 These differences are exhibited more easily by plotting 

 the average of all the plots as a straight line, and the aver- 

 age of the different groups as percentages of the total 

 average above and below the general average line. 



In observing Fig.l, we are first impressed with a marked 

 similarity in the performance of the European and Medi- 

 terranean alfalfas, on the one hand, and the American and 

 Turkestan on the other, and also with the striking differ- 

 ences exhibited between the two groups. Although the 

 average yield of the European plots greatly exceed that of 

 the Mediterranean plots, the shapes of their respective 



