206 Retrograde Varieties 



attained a height of 12 feet, but the season did 

 not allow its seeds to ripen normally. Only 

 a few kernels were developed before the winter. 

 From this seed plants of a wholly different 

 type came the next year, of smaller stature, and 

 with more brownish and rounded kernels. They 

 also flowered earlier and ripened a large num- 

 ber of seeds. The depression on the outer side 

 of the seed had almost disappeared, and the 

 original white had become darker. Some of the 

 seeds had even become yellow and in their 

 rounded form they approached the common 

 European maize. Obviously they were hybrids, 

 assuming the character of their pollen-parent, 

 which evidently was the ordinary corn, culti- 

 vated all around. The observation of the next 

 year showed this clearly, for in the third gener- 

 ation nearly all resemblance to the original and 

 very distinct American species was lost. If 

 we assume that only those seeds ripened which 

 reverted to the early-ripening European type, 

 and that those that remained true to the very 

 late American variety could not reach maturity, 

 the case seems to be wholly comprehensible, 

 without supposing any other factors to have 

 been at work than those of vicinism, which 

 though unknown at the period of Metzger's and 

 Darwin's writings, seems now to be fully un- 

 derstood. No innate tendency to run out and 



