240 



Journal of Agricultural Research 



Vol. XII. No. s 



zona-grown seed. For all such hills the height of each plant was re- 

 corded with the total length of the ear or ears. In this way each hill 

 constituted a unit of comparison. The height of each plant was ex- 

 pressed as a percentage of the mean height of the two plants in the 

 same hill. These determinations were then averaged to secure an 

 expression of the mean behavior of the plants from each source of seed. 

 Length of ear was treated in the same way. Table V gives the results. 

 Unfavorable conditions so reduced the yields at Lanham, Md., that length 

 of ear was recorded for only three of the strains, and even for these 

 there was so much variation that the results are of doubtful significance. 

 They serve, however, to supplement the results on the height, with which 

 they are in accord. 



Table V. — Average behavior of Maryland-grown seed expressed as a percentage of the 

 mean of Maryland- and Arizona-grown seed, igi6 



At Sacaton, Ariz., in 191 5 reciprocal crosses were made with Stock- 

 ton X Boone and Strawberry X Boone, and these reciprocals were sepa- 

 rately compared with the seed grown at Lanham, where Boone was 

 used only as the male parent. In all of the six comparisons except one, 

 transferring the seed resulted in increased height ; and in all but one the 

 difference is almost certainly not the result of chance. 



In 1915 the crosses in both Maryland and Arizona were made by hand 

 instead of by detasseling alternate rows as in 191 2. In gathering pollen 

 an effort was made to obtain pollen from as many plants as possible and, 

 so nearly as might be, in equal amounts from each plant. In like manner 

 selection of female parents was avoided so far as possible. In spite of 

 these precautions, it is evident that there would still be a measure of 

 selection. Some plants produce virtually no pollen, and many plants 

 fail to develop an ear. Furthermore, since the plants were thinned to a 

 stand of one in a hill from each locality, obviously weak plants being 

 removed, it would seem that here too there would be a tendency to retain 



