20 VALUE OF FIRST-GENERATION HYBRIDS IN CORN. 



two inbred strains which without crossing were among those which 

 gave the lowest yields of any represented in the experiment. 

 Regarding other crosses, Doctor East states: 



In the remainder of the field every possible combination of dent, flint, and sweet 

 maize was grown, and in every case an increase in vigor over the parents was shown 

 by the crosses. It is to be regretted that comparable yields could not be obtained 

 in every instance, but, as a matter of fact, the differences were so apparent to the 

 eye that it is almost unnecessary. The figures presented do not show the average 

 increase to be expected by a cross. The manuring was heavy, the cultivation inten- 

 sive, and the yields were beyond the ordinary. But they do show that in practically 

 every case a combination of two high-bred varieties, of seed corn is more vigorous 

 than either parent. a 



A NEW SERIES OF HYBRIDS BETWEEN DIVERSE TYPES. 



The crosses thus far considered have in all cases been between 

 strains that are comparatively closely related. The most violent 

 crosses are among those reported by McChier where varieties of 

 sweet and dent, pop and dent, and sweet and pop corns were included. 

 The diversity between these types may seem considerable, represent- 

 ing as they do the extremes of the types now cultivated in the United 

 States, but looked at botanically these varieties appear closely 

 related when compared with the very diverse types that exist in the 

 Tropics. 



Over the whole of the United States the interchange of seed has 

 been so extensive and the culture is so nearly continuous that all 

 characters are to a great extent shared by the whole series of varie- 

 ties, even the most divergent types being distinguished by charac- 

 ters that differ in degree rather than in kind. Even before the advent 

 of the white man the nomadic tendencies of the North American 

 Indians must have operated against any complete isolation of types. 



The sedentary habits of the Indians of tropical America are in 

 strong contrast with those of the more northern tribes, and together 

 with the great diversity of natural conditions have operated to 

 produce an enormous number of very distinct types, showing numer- 

 ous specialized adaptations to different conditions, the agricultural 

 significance of which is only beginning to be appreciated. 



As an instance of one of these divergent groups there may be men- 

 tioned a type of corn cultivated in parts of the lower plateau of 

 Mexico in a region that receives such scanty rainfall that similar 

 regions in this country would be thought entirely unsuited for corn 

 growing. This corn is so different from the types with which we are 

 familiar that it was given specific rank by Bonafous and named 

 Zea Jiirta} The leaf sheaths are densely covered with long hairs 



oOp. cit., pp. 179-180. 



& Bonafous, M. Annales des Sciences Naturelles, vol. 17, 1829, p. 156. 

 191 



