lo kempton: ancestry of maize 



familiar with teosinte are well aware of the fact that the female 

 spikes often terminate in staminate tips. These staminate tips 

 correspond to the same phenomenon on the ears of maize, but the 

 occurrence of entirely male spikelets definitely located at the 

 less specialized tip should not be confused with perfect flowered 

 spikelets located in the alveoli of the highly specialized rachis 

 at the base of the spike. The occurrence of sharply differ- 

 entiated staminate tips on the pistillate spikes of teosinte seems 

 to emphasize, rather than minimize, the greatly specialized 

 nature of the female inflorescences. The transition from single 

 pistillate to paired staminate spikelets is abrupt and is accom- 

 panied by an equally abrupt change in the rachis and glumes. 



It must be repeated that there is a complete absence of func- 

 tioning stamens in the specialized pistillate portion of the spikes 

 of teosinte, while in maize perfect-flowered spikelets not only 

 have been found throughout the entire ear, but strains breeding 

 true for this condition have been isolated. The fact that all 

 species of the Maydeae are structurally bisexual should not be 

 allowed to obscure the importance of this point. 



A careful study of teosinte, not only in the large commercial 

 plantings of Mr. Heinisch in Florida, but also in widely diverse 

 environments and under carefully controlled breeding experi- 

 ments, together with a study of hybrids between the Floridian 

 and Mexican types, fails to show a variation at all comparable 

 with that observed in even carefully bred varieties of maize. 

 The chief support of a hybrid origin for maize lies not only in 

 single character differences or similarities but also in the more 

 general features which have been overlooked or lightly dismissed 

 by Weatherwax. The greater frequency of variation in maize 

 compared to almost any other species seems to the writer to 

 offer a very reasonable ground for doubting its simple evolution 

 from the same common ancestor with Euchlaena and Tripsacum. 



Aside from the extreme variability, it is hard to understand, 

 with Weatherwax's theor}% how, sharing as they did the same 

 habitat, Zea and Euchlaena ever became differentiated. They 

 hybridize readily, the hybrids are perfectly fertile, and they 

 become indistinguishable when grown together. 



