WEATHERWAX: THE EVOLUTION OF MAIZE 329 
Hybrid origin of maize.—A new variety of corn known as Zea 
canina was reported from Mexico about 1890, and Bailey (1) 
and Harshberger (17) concluded that it was the long-sought wild 
ancestor of the species, the latter making it the basis of his mono- 
graph on corn. But correspondence with Mexicans who knew 
the plant showed that Zea canina could be produced at will by 
hybridizing teosinte and ordinary maize. Accordingly, previous 
conclusions had to be revised, and along with Harshberger’s 
revision (18) came the suggestion of three possible explanations 
of the botanical nature of maize: (1) that maize is a distinct 
species; (2) that maize originated as a hybrid between teosinte and 
some unknown grass; and (3) that maize is the result of a cross 
between teosinte and some variety of teosinte which had been 
changed by cultivation. He favors the last-named possibility, 
and in his latest expression on the subject (21, pp. 398-399) 
this is the only theory given. 
His conclusions were reached as a result of hybridization experi- 
ments with maize and teosinte, in which a graded series of inter- 
mediates between the ear of the one and the female spike of the 
other were produced. A series of this Kind always suggests 
evolution, but this one does not possess the advantage of having 
maize at one end and its two hypothetical ancestors at the other. 
Moreover, the status of the hybridization problem at the time 
at which this theory was proposed (1896) and the evolutionary 
influences attributed to cultivation, especially to irrigation, do 
not show up so well alongside the genetics of this later day. 
Collins’s theory (9) is similar to the second possibility suggested 
by Harshberger; that is, he thinks that maize originated in a 
cross between teosinte and some unknown grass similar to pod 
corn and belonging to the Andropogoneae. With respect to a 
large number of characteristics, ordinary maize is shown to be 
intermediate between the primitive pod corn and the highly 
specialized teosinte; and this is considered evidence that Zea is a 
hybrid between the two extremes. 
Although this theory is the most elaborate and the most 
widely accepted of all the attempts that have been made to 
explain the origin of maize, yet it falls short of its aim in some 
respects. Granting the accuracy of the observations upon which 
