ratio do synapse and exchange segments. The fact that 
corn and ‘Tripsacum can be hybridized betokens some 
measure of homology between their chromosomes; and 
if this homology does exist, differences in length and arm 
ratio need not prevent the exchange of segments. Just 
how extensive this exchange should be to meet the re- 
quirements of the hypothesis of the hybrid origin of teo- 
sinte is impossible to estimate. But, if the rate were ex- 
tensive, in the sense of being unrestricted or only slightly 
restricted, we should expect corn and Tripsacum to have 
merged into one continuous though highly variable 
group, with little or no barrier separating the parental 
species from each other or from their hybrids. 
Weatherwax (53) states that polyembryony, apomixis 
and chromosomal variation in Tripsacum, as reported by 
Farquharson, serve to increase the doubt that a corn- 
Tripsacum cross could have given rise to the ‘‘stable and 
relatively uniform plant that teosinte is.’’ Such an opin- 
ion needs some expansion in order to be convincing, for 
Weatherwax makes no attempt to point out whether or 
not it is based on any cytological or genetical principle. 
In its present form, this opinion is another non sequitur 
requiring no further discussion here, 
THE TRANSFER OF CHROMOSOME KNOBS FROM 
TripsacuM to TROSINTE AND CORN 
Extensive objections (81, 82) have been raised to our 
view that chromosome knobs have been transferred from 
Tripsacum through teosinte to corn, on the grounds that 
the knobs are mostly terminal in ‘Tripsacum but mostly 
intercalary in corn, and that such a transfer would require 
chromosomal rearrangements, for whch there is little 
evidence. 
We have stated at least twice (26, 36) that if it were 
explained how corn, monophyletic as it is sometimes 
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