174 THE AMERICAN NATURALIST [Vol. XLV 



scarcely do more than speculate in regard to the specific 

 characters that are concerned in developing either organs 

 or individuals of certain sizes. There are probably many 

 characters that interact together in developing certain 

 characters, although the actual determinants in the germ 

 cells may be transmitted independently. These interde- 

 pendent reactions during development obscure to us the 

 real causes and what we regard as independent char- 

 acters may be but indirect results of unknown causes. 

 For example, the ability to evert their starch when heated 

 has been the distinguishing character of the subspecies 

 called Zea mays everta, the pop maizes. This character 

 so called, however, is the resulting physical condition of 

 the starch caused at least partially by the small size, the 

 thickness and the toughness of the enveloping pericarp. 



For these reasons it may not be possible — at least very 

 soon— to point out even the number of characters con- 

 cerned in size developments. From the number of ex- 

 treme segregates obtained in each case I might venture 

 to state that the size of ear in the cross shown in Fig. 

 5 is apparently due to not less than three characters, 

 while the size of ear in the other cross pictured seems 

 to be due to not less than four characters. 



