MAIZE BREEDING 



197 



justification apparently rests on a firm genetic foundation. As 

 yet practical demonstrations of improvement in corn by the 

 application of Mendelian principles are unavailable. 



Relation of Ear Characters to Yield. Corn shows have accom- 

 plished much in teaching growers the characteristics of various 

 standard varieties. They have, however, over-emphasized the 

 value of ear type as a means of corn improvement. Much work 

 has been carried on with the view of determining the relation 

 between various ear and plant characters and ability to give 

 high yields. In general, no single character has been found to be 

 so closely related with yielding ability as to be of much value 

 from the standpoint of selection. Too close uniformity of type 

 probably tends to reduce yield, for we have learned that self- 

 fertilization in corn causes a marked decrease in growth vigor as 

 compared with cross-fertilization. 



For the purpose of illustrating the general nature of results 

 in this field, the work of Williams and Welton (1915), in Ohio, 

 may be used. They compared the yields of ears selected on the 

 basis of wide differences of type. In the majority of cases 

 selection was continuous, i.e., long ears from the long strain and 

 short ears from the short strain. Summarized results are given 

 in Table XLIV. 



TABLE XLIV. RELATION BETWEEN EAR CHARACTERS AND YIELD 



These differences are very small considering that the yields 

 obtained averaged between 60 and 70 bu. per acre. Although 

 continuous selection isolated strains which differed consider- 

 ably from each other, the yields were not markedly affected. 

 The progressive change in shelling percentage of the progeny was 

 most striking and illustrates how corn may be modified by selec- 

 tion (see Table XLV). 



