IMPROVEMENT OF VARIETIES 87 



with the ear borne high would not be in harmony with 

 natural conditions, and experience has shown that varieties 

 having these characters do not yield so well as the native 

 type. Also, at the Nebraska station, when comparison 

 was made between broad-leaved and narrow-leaved 

 strains in dry years, there being an excess of sunshine and 

 limited water supply, the largest yields were obtained from 

 narrow-leaved strains.^ In one year, with excessive rain- 

 fall, broad-leaved types gave larger yields. While broad 

 leaves elaborate starch, they also evaporate water at a 

 rapid rate ; hence, the most desirable leaf area on corn 

 plants must be a balance between the moisture supply 

 on the one hand and sunshine on the other. 



While under rather abnormal conditions for growth, 

 as a dry climate, attention must be given to the character 

 of plant growth, yet under normal conditions a wide range 

 is permitted. In Illinois, where selection for height of ear 

 was continued for six years, there was no marked difference 

 in yield between the high-ear and low-ear types, and the 

 same was also true when angle of ear was considered. 



It may be assumed that when selection is made for 

 yield, all other characters of the plant will adjust them- 

 selves under the given conditions ; so that ultimately the 

 type of plant giving best yield under those conditions will 

 result. However, under certain conditions in the South 

 the ears are borne verj^ high, and in the North, in some 

 cases, the ears are borne very low. In both these cases, 

 for convenience in harvesting, it would be well to select 

 for a more desirable height of ear. There are many in- 

 stances where selection to modify some character of the 

 plant would be justified, even though the yield was not 

 affected. 



1 Nebr. Agr. Exp. Sta., 24th Ann. Rpt., p. 158. 



