BEGINNINGS OF THE HETEROSIS CONCEPT 23 



two rows from the same parent ear, through an oversight, were not kept 

 separate. No further detasseling was done. Since the self-fertilized plants 

 could not be detasseled and still utilized for selling, the method of controlling 

 cross-fertilization by detasseling would prove a distorting factor in comparing 

 the effects of selling and crossing. 



Consequently, no detasseling was practiced in any of my subsequent ex- 

 perimental work with corn, but every pollination was controlled by bagging 

 with glassine bags and manipulation by hand. The bags were tied in place 

 by ordinary white wrapping-cord passed once around and tied with a loop 

 for easy detachment. Each plant was labeled at the time of crossing with a 

 wired tree-label attached to the stalk at the height of the operator's eyes, 

 and marked with the exact identification of the plant to which it was attached 

 and the source of the pollen which had been applied. On harvesting these 

 hand-pollinated ears, the label was removed from the plant and attached 

 securely to the ear, thus assuring that the ear and its label would remain 

 permanently associated. A third row (A 19) from an ear having 22 grain-rows 

 was added to improve the chances of finding ears with still higher numbers 

 of grain-rows. 



In November, 1905, these 19 pedigree cultures were carefully harvested 

 by my own hands and the grain-rows counted, with the results tabulated in 

 Table 2.1. 



The only observation noted on these 1905 cultures was that there was no 

 clear indication of mutations or segregations of any kind, but the aspect of 

 the field was that of any ordinarily uniform field of corn. Row counts did 

 show the expected indication of Galtonian regression, in that the parents 

 with low numbers of grain-rows produced progenies having lower numbers of 

 grain-rows than did the ears having higher than average numbers of grain- 

 rows. Thus, the two ears with 10 rows of grains each had the average of 13.2 

 rows of grains on their progeny ears. The two 20-rowed ears showed an aver- 

 age of 15.5 rows of grains on their progeny ears. The three 22-rowed parent 

 ears produced progenies with an average of 17.5 rows of grains. 



The same general plan was followed in 1906, except that the pollen for 

 the crossbred cultures was no longer taken from the plants set aside for 

 selfing. The reason for this change, as specifically stated in my notes written 

 at the end of the 1906 season, being "to avoid the deleterious effects of self- 

 fertilization in the cross-fertilized series." This indicated that at the end of 

 19C6 I had only the concept held by Holden, Shamel, East, and all other 

 corn breeders who had had experience with the selfing of maize — that selfing 

 has deleterious effects, not that crossing has advantageous effects other than 

 the simple avoidance of the deleterious effects of selfing. 



The new method of handling the crossbred cultures was to divide each 

 such culture by a marker set at the midpoint of the row. All the plants in 

 these rows were bagged. Mixed {)ollen from the plants in the first half of the 



