mosomes of the two species are morphologically similar 
and synapse more or less normally in the hybrids (2, 3, 
4, 19, 20, 21); (c) The arrangement of the gene loci al- 
though probably not identical in the two species is cer- 
tainly similar (11); (d) Crossing over between linked loci 
in maize and teosinte chromosomes is, with few excep- 
tions, of the same order as it is in corn (11). In view of 
these facts, it is difficult to see how, once hybridization 
has occurred, gene exchange could be prevented; and 
there is ample evidence that it has not been. 
Collins (8) noted many years ago that the teosinte in 
the vicinity of Chalco in Mexico is quite maize-like in its 
characteristics, including plant color and pilosity of the 
sheaths. The first of these characters involves at least one 
gene either B or FR and the second at least two (39). In 
being transferred from maize to teosinte, these genes have 
undoubtedly carried with them blocks of closely linked 
genes which accounts, at least in part, for the fact that 
the teosinte of Chalco is among the most maize-like varie- 
ties in many other respects. Randolph (41), himself, has 
found yellow endosperm, a maize character, in teosinte, 
and Mangelsdorf (28) has reported both yellow endo- 
sperm and colored aleurone. 
There is no doubt that the teosinte of Mexico is more 
maize-like than that of Guatemala in its general aspects 
(18), in cytological features (21, 24, 25) and in genetic 
characteristics (47, 48, 49). Reeves (44) found a hybrid 
of the Mexican teosinte Nobogame x New to have uni- 
formly paired spikelets, a so-called ‘‘generic’’ character 
of Zea, distinguishing it from teosinte. These facts re- 
quire explanation, and the simplest and most commonly 
accepted one is that the Mexican teosintes have, on the 
average, undergone more admixture with maize than 
have the Guatemalan varieties. Longley’s explanation 
of the cytological differences as the product of ‘‘gradi- 
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