within a crop plant and of their relations with culture 
complexes. Such races have been studied in some degree 
for two Middle American crop plants, maize and cotton 
(104, 213). In each case it has been pointed out that the 
development of these races must have occurred in partial 
isolation and must have been related to cultural centers. 
It is for this reason especially desirable that extensive col- 
lections, if not studies, of truly native crop plants should 
be made before they are further decimated by the impact 
of modern cultural changes. 
For the present paper, material has been drawn from 
the literatures of botany, ethnology and archaeology, but 
no pretense is made of a complete coverage of any one. 
A better representation of the historical writings of the 
earlier Spanish explorers would be especially desirable, 
but it is a subject worthy of study in itself. Several of 
the important references in this field are cited, but none 
has received the time and attention which it deserves. 
Some cultivated species may have been overlooked. It 
is hoped, however, that most of the important cultivated 
plants have been included, particularly those which have 
changed in their biological nature and their distribution 
through their association with man. One cannot, in a 
paper of this scope, list all the useful wild plants of 
Mexico, though the more important of these were doubt- 
less planted at times by the early Mexicans; information 
is meager or lacking for those which have been intention- 
ally omitted. ‘The evaluation of the published informa- 
tion has in some cases been aided by frequent reference 
to herbarium material and by some field experience. It 
should be borne in mind that the peoples of this region 
had developed both agriculture and horticulture to a 
rather high degree and actually possessed botanical gar- 
dens which were, at the time, unrivaled among the Euro- 
pean peoples. 
| 28-4 
