rachis diameter from 7.0 mm. to 8.9 mm. in the period 
represented by the remains of maize in this cave. 
Increase in Variation 
More conspicuous than the increase in the size of the 
rachis is the increase in variation of the cobs. Several of 
the earliest cobs from the 1950 collection resemble the 
prehistoric wild corn from the Tehuacdn site but not all 
Tasie II. Rachis diameters (mm.) and kernel-row-numbers of the 
cobs from successive levels of Bat Cave. 
Level | Rachis Kernel-row-numbers 
Inches | Diam.Av.|No.Cobs| —g 10 12 14 16 18 | Av. 
0-12 8.9 70 8 20 28 12 2 11.4 
12-24 7.8 99 10 25 35 22 4 3 {11.8 
24-36 7.9 120 12 30 55 16 2 {10.2 
36-48 7.2 142 28 42 54 13 5 10.9 
48-60 7.0 13 | 9 1 g 10.6 
No.Cobs) 430 | 444 | 59 |126 [173 | 65 | 16 | 5 | 
of them are of this type. The majority of them are small 
but there is considerable variation in their other charac- 
teristics, especially in the size and shape of cupules. 
There is some evidence that introgression with teosinte 
had already occurred in some of the cobs from the lowest 
level. Based on the characteristics of the cobs we con- 
clude that the corn from the 48-60” level in Bat Cave, 
as already mentioned, is later than the corn of the Abejas 
phase in the Tehuacan sites and earlier than that of the 
Ajalpan phase. 
The evidence of teosinte contamination is even more 
clear-cut in the specimens from the 86-48” level than in 
the 48-60” level. Photographs of several specimens with 
indurated tissues and solitary pistillate spikelets are illus- 
trated in Plate I, C and E. 
The cobs in this and subsequent levels are so hetero- 
[9] 
