completely proportional to the number of knobs and this 
may suggest that the Awd as well as the amount of 'Trip- 
sacum germplasm is a factor in the results. 
In any event the high-knob group is not a homoge- 
neous one, and it represents a complex mixture of char- 
acters derived from pure maize on the one hand and from 
Tripsacum on the other. The task of recognizing and 
classifying its races will be a formidable one even with the 
useful diagnostic characters which Anderson and Cutler 
(2) have brought to bear upon the problem of racial dif- 
ferences in maize. 
The relative homogeneity of the low-knob group as 
contrasted with the marked heterogeneity of the high- 
knob group is not in keeping with Longley’s suggestions, 
discussed in greater detail later, that a high-knob num- 
ber signifies primitiveness. For, regardless of whether the 
characters which we have considered are primitive or 
otherwise, it would seem to be a difficult evolutionary 
step to bring together in the low-knob or ‘‘advanced”’ 
group all of the characteristics which are scattered at 
random through the varieties of the high-knob or “‘prim- 
itive’’ group. Evolution seldom, if ever, operates in this 
direction. 
INTERPRETATION AND CONCLUSIONS 
How are we to interpret the various facts revealed by 
these studies of Guatemalan maize? 1. the great diver- 
sity in external morphological characters as well as in 
internal chromosome morphology; 2. the concentrated 
diversity occurring in one small area in Huehuetenango 
where teosinte is found in the wild and Tripsacum grows 
in profusion; 8. the relationship between knob numbers 
and other characteristics; 4. the restriction of low-knob 
varieties to high altitudes; and 5. the fact that practi- 
‘ally all low-knob varieties are identical in certain char- 
[ 236 ] 
