WEATHERWAX: THE EVOLUTION OF MAIZE 311 
of the plant. The writer has made a thorough study of many 
varieties of corn, probably representing the full range of varia- 
bility of the species, and other species of the Maydeae have been 
examined in detail by way of comparison. As a result of these 
studies, a theory is here proposed, which is believed to explain, 
in a manner more consistent with known facts, the evolution of 
maize. 
Acknowledgment is here made of valuable assistance received 
in this study from a number of sources. The investigation is an 
outgrowth of a problem suggested to me five years ago by Pro- 
fessor D. M. Mottier, who has since then also aided me with many 
suggestions and criticisms. American consuls in several cities of 
Central and South America have assisted me in getting seeds of 
many varieties of corn; and very material assistance of the same 
kind has been given me by a large number of friends in this 
country. The Bureau of Plant Industry has supplied me with 
seeds of corn and teosinte. Rhizomes of Tripsacum were obtained 
from the Missouri Botanical Garden. The late Mr. Juan J. 
Rodriguez, of Guatemala, sent me rhizomes of a species. of Trip- 
sacum and seeds of a number of varieties of corn; he also told me 
of many interesting observations that he had made on the grasses 
of Guatemala. Mr. George F. Will, of Bismarck, North Dakota, 
supplied me with seeds of thirty varieties of corn collected from 
Indian reservations. Mr. A. Heinisch, of Clarcona, Florida, 
sent me seeds and morphological material of teosinte, aided me in 
making observations in his teosinte fields in the summer of 1917, 
and gave me the benefit of many observations that he had made 
as a grower of the plant. 
CLASSIFICATION 
The tribe Maydeae includes a number of grasses characterized 
by unisexual spikelets, the male being above the female, in the 
same or in different inflorescences. The seven genera of the tribe 
fall naturally into two classes.. Zea, Euchlaena, and Tripsacum 
bear evidences of close relationship and are all native of America. 
Having the same general characteristics as these, but differing 
from them somewhat in appearance and detailed structure, are 
four genera, Coix,, Chionachne, Sclerachne, and Polytoca, which 
