6. There is a progressive increase in cob and kernel 
size from stratum to stratum. 
7. Since ancient types did not disappear completely 
when new types came into existence, there is a progres- 
sive increase in total variability from stratum to stratum. 
This factor is believed to be of particular significance in 
the evolution of cultivated plants in general. 
8. Changes in alleles at the J'u-tu locus and an intro- 
gression of teosinte are believed to be the two most im- 
portant factors in the evolution of maize. These involve 
a progressive increase in the size of the rachis and the 
vascular system of the ear, a reduction in the size of the 
glumes, a shortening of the distance between the rachis 
and the base of the kernels and a hardening and stiffen- 
ing of rachis and glume tissues. 
9. The problem of where maize originated as a wild 
plant is not solved by the new evidence. 
ACKNOWLEDGMENTS 
It would be difficult to acknowledge the full extent of 
our indebtedness to Mr. Herbert W. Dick, whose cap- 
able leadership made possible the success of the 1948 Bat 
Cave Expedition and whose recognition of the impor- 
tance of vegetal remains is directly responsible for the 
archaeological material upon which this paper is based. 
We are also grateful to Mr. Gordon W. Dillon for his 
reconstruction of primitive maize and to C. Parker 
Mangelsdorf for the diagrammatic illustrations of cross 
sections of various types of ears. 
[ 244 ] 
