MAIZE— KEMPTON 405 



establish a parent and offspring relationship. These two great tribes 

 of grasses are clearly related, so that for the members of one to have 

 some characteristics of the other is no more than is to be expected 

 even though the relationship is distant. 



The chief objection to the origin of com by the hybridization of 

 its known wild relatives with some other grass lies in the uncertainty 

 of what grass constituted the other parent. The sorghum tribe is 

 made up largely of Old World grasses, none of which were known to 

 have been introduced into the New World until quite recently. So 

 far as is now known none of the members of the sorghum tribe has 

 chromosomes that resemble those found in maize, though the two 

 tribes have identical chromosome numbers. Further attempts to 

 hybridize corn and sorghum and sorghum and teosinte have failed 

 repeatedly. 



This failure to obtain hybrids, however, may merely mean that 

 the proper conditions or the proper parents have not been tried. 

 Hypothecating an unknown parent, is not greatly different from con- 

 cluding that maize developed from a wild form now extinct except 

 that it does not close the door so effectively against the possibility of 

 recreating maize. The time factor required to stabihze the hybrid 

 and distribute the finished product throughout the New World would 

 probably be somewhat less than that required on the rejected hypo- 

 thesis of major mutations but either would require a very long time. 



Aside from the fact that it begs the question, the beUef that maize 

 was domesticated from a pre-maize species by selection leaves wholly 

 unexplained the interfertihty of maize and teosinte, if the relationship 

 of these genera is so remote they would not be expected to produce 

 fertile offspring when crossed. It also has all of the defects of the muta- 

 tion theory in respect to the lack of evidence of primitive maize in 

 the earhest burials. Further, teosinte so far as tested seems to have 

 allelomorphs of the identified genes of maize. In some cases not only 

 are the dominant allelomorphs of the maize genes present in teosinte 

 but they are accompanied by modifying genes and in other cases 

 teosinte possesses genes recessive to those dominant in maize. Clearly, 

 the relationship of these genera is intimate, but whether they stand 

 in the relation of parent and offspring cannot now be determiaed. 



If teosinte and maize are on widely different branches of the corn 

 family tree, as the hypothesis of the development of corn from an 

 extinct cornlike ancestor requires, it would be expected that hybrids 

 between the two genera would be intermediate in nature. Genes 

 which in maize have a clear-cut dominant and recessive reaction 

 should behave as intermediates without clear-cut dominance when 

 mated with their allelomorphs in teosinte. This expectation follows 

 from the explanation of the origin of dominance through the accumu- 

 lation of genes tending to transform the intermediate condition 



