igO THE CEREALS IN AMERICA 



256. Crossing. — What influence the crossing which the detas- 

 seling of alternate rows of maize compels has upon the subsequent 

 progeny is not shown in the experiments just related, since to 

 determine this it is necessary to grow the seeds thus crossed. 



The Illinois Station 1 crossed a number of varieties in 1892, grew the cross-bred 

 varieties in 1893 and again in 1894, comparing the yield with the average yield of 

 the two parent varieties. In 1894, in four out of six cases, the yield was greatest 

 for the cross, the average increase being twelve bushels per acre. In 1893 three out of 

 four gave the largest yields for the cross, the average increase being two and three- 

 tenths bushels per acre; and in 1892 five crosses gave in every case a larger yield 

 than an average of the parent varieties, the average increase being nine and a half 

 bushels per acre. The conditions under which it was necessary to conduct these 

 experiments made the results inconclusive. 



When McCluer^ raised crosses from different types of maize, 

 the progeny from the full cross was in nearly all cases increased 

 in size as a result of the crossing. In nearly all cases this in- 

 crease in size w^as not marked the second year, although yet 

 larger than the average of the parent varieties. This may have 

 been due to a tendency to revert to the character of the original 

 ancestor or may have been due to each plat being grown from 

 a single ear, thus bringing about at once inbreeding. 



257. Disposition to Maintain Types and Varieties. — When 

 sweet maize is crossed with a dent variety the grains of the 

 current cross on the ear may all assume a smooth rounded 

 appearance not unlike a flint variety. The plants that grow from 

 these grains will produce ears which will have some grains of 

 the dent type and some of the sweet type, thus showing a ten- 

 dency to split up into the separate types and to prevent the 

 production of an intennediate type. The same tendency is 

 somewhat apparent, although less noticeable, in crosses between 

 varieties of the same type. While the readiness with which 

 maize cross-fertilizes tends to obliterate varieties, this tendency 

 opposes it. (278) 



1 IlL Bui. 37, p. 2a 



2 111. Bui. 21, pp. 95-96. 



