tion. A passage in the introduction to ‘‘On the Origin 
of Species’’ makes this abundantly clear: 
At the commencement of my observations it seemed to me probable 
that a careful study of domesticated animals and of cultivated plants 
would offer the best chance of making out this obscure problem. Nor 
have I been disappointed; in this and in all other perplexing cases I 
have invariably found that our knowledge, imperfect though it be, of 
variation under domestication, afforded the best and safest clue. I 
may venture to express my conviction of the high value of such stud- 
ies, although they have been very commonly neglected by naturalists. 
Darwin’s studies on domestic animals and plants, to- 
gether with those of De Candolle on the origins of culti- 
vated plants, have been the inspiration for our own work, 
at once more restricted in its scope and more intensive 
in its treatment, on the origin of Indian corn. It is now 
twenty years since we proposed the tripartite theory” 
which postulates (A) that cultivated maize originated 
from a wild form of pod corn which was once indigenous 
to the lowlands of South America; (B) that teosinte (Zea 
mexicana), the closest relative of maize, is the product 
of a natural hybridization of Zea and 'Tripsacum which 
occurred after cultivated maize had been introduced by 
man into Central America; (C) that new types of corn 
originating directly or indirectly from this cross and ex- 
hibiting admixture with Tripsacum or teosinte comprise 
the majority of modern Central American and North 
American varieties. 
During these twenty years, an impressive volume of 
new research bearing on the problem has been completed, 
much of it stimulated and guided by the theory itself. 
*In this paper we, like other students of maize, use the word 
““theory’’ in its popular or semipopular meaning. In a strict sense, 
we are not dealing with theories — certainly not with theories involv- 
ing broad principles — but with hypotheses. Webster’s Dictionary 
defines hypothesis as ‘‘a tentative theory or supposition, provisionally 
adopted to explain certain facts and to guide in the investigation of 
others. ”’ 
[ 830 ] 
