tral Asia from Persia and Turkestan to Tibet and Siberia 
where it now occurs, without leaving a single prehistoric 
trace of any kind. Yet there is no tangible evidence of 
the existence of maize in Asia or any other part of the Old 
World before 1492. When we consider how thoroughly 
other economic plants were treated in the extensive 
ancient literature of Asia and the Near East, and how 
popular maize became as a cultivated plant and as a sub- 
ject for artistic treatment after the discovery of America, 
it taxes our credulity to believe that all of the civilized 
people of the Old World could have remained ignorant 
of a food plant at once so widely distributed, so peculiar 
in its characteristics and so useful to mankind. 
Burkill (1935), probably the leading authority on the 
economic plants of the Far East, came to a similar con- 
clusion. He states: ‘‘The strongest reason against the 
belief [of a pre-Columbian distribution of maize in China] 
lies in the unanswerable argument that no plant of such 
value could have remained hidden in the Far East, if 
there.’”’ 
Actually the absence of Race A in the coastal regions 
of Asia is not difficult to explain, if indeed it requires 
explanation. In the first place, its absence among the 
very limited collections so far made from the coastal re- 
gions of Asia is far from conclusive proof that it does not 
occur. But if we assume for the purpose of discussion 
that Race A actually is absent at low altitudes in Asia, 
then there are several possible explanations which do not 
require the assumption of pre-Columbian diffusion. An 
obvious one is that the more productive Tripsacoid vari- 
eties of the second race, Race C, have already, in coastal 
regions, largely replaced the non-vigorous unproductive 
varieties of Race A, earlier introduced, as they are per- 
haps in the process of doing in the hills where Race C 
now also occurs along with Race A. The counterpart of 
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