facts, and so far as we can determine, is in keeping with 
the facts of genetics, cytology, morphology and anthro- 
pology. Two minor details are lacking; the picture does 
not show how widespread the culture of pure maize had 
become before the hybridization with Tripsacum and it 
does not fix the date at which this hybridization occurred. 
These are questions which may be answered when studies 
of maize from other Central American countries and 
Mexico have been completed, and when botanical and ar- 
chaeological data have been more completely correlated. 
ALTERNATIVE INTERPRETATIONS 
So far we have discussed relationship between knob 
number and other characteristics only in terms of ‘T'rip- 
sacum admixture as postulated by Mangelsdorf and 
Reeves. There are two other hypotheses on the origin of 
maize which may be considered, that of Montgomery 
(19) and Weatherwax (22) which has maize, teosinte and 
Tripsacum deriving independently from a remote com- 
mon ancestor and that of Ascherson (3) which has maize 
deriving directly from teosinte. The limitations of both 
of these hypotheses in accounting for all of the facts have 
been discussed elsewhere (18). It should be pointed out, 
however, that the particular data presented in this paper 
can, without too much difficulty, be interpreted in terms 
of either of these alternative hypotheses, if other evidence 
bearing on the question is ignored. 
Longley (15,16) has recently elaborated upon Ascher- 
son’s theory in interpreting the chromosome knob situ- 
ation in the three American Maydeae and in drawing a 
picture of their possible relationship. A brief abstract of 
his conclusions follows: 
The chromosomes of each species possess a definite and 
characteristic number of knob forming points. In 'Trip- 
sacum and Guatemalan teosinte these points are more 
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