resent a period during which such basic culture elements 
as agriculture and pottery-making were first spreading 
from Mexico to the Southwest. It is a satisfaction to 
be able to report that these hopes have been, in part at 
least, realized. 
In 1952, 1953, and 1955, twelve caves in northwestern 
Mexico were excavated, five of which contained speci- 
mens of prehistoric maize. This paper will not attempt 
to describe or discuss the archaeological features of these 
caves in any detail since areport on this subject is near- 
ing completion and will soon be published. The brief 
archaeological summary and descriptions of cultural 
stratigraphy which follow are intended only to “‘set the 
stage’’ for the discussion of the maize recovered during 
the excavations. 
The caves investigated are located in the Sierra Madre 
Occidental of northwestern Chihuahua and northeastern 
Sonora, Mexico. Most of the Sierra Madre in this area 
is a plateau surface into which rugged canyons have been 
cut by stream action. The plateau averages more than 
5,700 feet in elevation, with a maximum rise to over 
8,200 feet along the crests of the highest ridges. Dis- 
sected basins separated by low ridges occupy the areas 
between canyons. Geologically, the Sierra Madre is 
composed of a long series of effusives, volcanic material 
or surface lava, generally lying above intrusive rocks such 
as porphyry, diorite, and andesite. In places, andesite 
and rhyolites compose the higher ridges. Conglomerates 
and sandstones fill a number of old basins. Fertile soils 
produced by weathering of the volcanic mantle exist in 
the dales, basins and lower slopes of the ridges. The 
climate is predominantly temperate; however, one of 
Mexico’s cold poles is in the higher mountains. Nearly 
three-quarters of the total annual precipitation of 24 
inches falls in the summer months of July, August, and 
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