The first objection is plainly contrary to the facts. It 
may be true, as Randolph suggests and as others have 
recognized (8), that there are partial genetic barriers to 
the free hybridization of corn and teosinte in nature. 
Certainly the number of recognizable hybrids found in 
localities where the two species are growing together in 
the same fields, and flowering at the same time, is less 
than might be expected in view of the fact that both spe- 
cies are monoecious and wind pollinated and that abun- 
dant opportunities for hybridization apparently exist. But 
the barriers, whatever their nature, are by no means com- 
plete, and every student of the problem from Harsh- 
berger on has been aware of natural hybridization of corn 
and teosinte (8, 16, 18, 80, 41). Randolph, himself, has 
furnished the most convincing evidence of this hybridi- 
zation, when he counted 45 Fy; hybrids in five days of 
travel in a limited region near the villages of Nojoya and 
San Antonio Huixta in Guatemala. If this small sample 
is representative, there must be thousands of new hybrids 
produced each year. That Randolph personally failed to 
find hybrids near Chalco in Mexico is of no significance, 
for others (18, 80) have done so. 
That maize and teosinte hybridize in Mexico and 
Guatemala must be accepted as an established fact and, 
if the frequency of that hybridization is less in any one 
place at any one time than some botanists expect, it must 
be remembered that it has been going on in countless 
localities for many centuries. 
The extent to which this hybridization results in gene 
exchange is not easily measured with precision, but it 
cannot be denied that there is some exchange. This would 
be expected on the basis of the following well-established 
facts: (a) The F; hybrids of corn and teosinte are usually 
vigorous and highly fertile and are easily backcrossed to 
either parent to produce fertile progeny; (b) The chro- 
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