tween altitude and knob number. Precise data on alti- 
tudes of the thirty-eight localities included in this study 
are not available but approximate altitudes were deter- 
mined from a topographical map prepared by Dr. Mc- 
Bryde from original surveys and other sources. In spite 
of the lack of precise data there is a highly significant 
relationship (P is less than .01) between number of knobs 
and altitude of the locality from which the maize was 
collected. Maize with one or three knobs was collected 
at altitudes averaging approximately 8000 feet. Maize 
with fifteen or sixteen knobs was collected at altitudes 
averaging 2000-2500 feet. Intervening values show ap- 
proximately a linear relationship. 
We interpret this relationship to mean that the non- 
Tripsacoid or Andean type of maize introduced from 
South America was then, as it is now, poorly adapted to 
culture at low altitudes. If it was grown at all at low al- 
titudes, it was immediately replaced by Tripsacoid maize 
as soon as the latter had come into existence. At high 
altitudes, however, the pure maize has been able to hold 
its own. A similar situation has already been reported 
for South America where knobless types predominate in 
the Andean regions of Peru, Bolivia and Ecuador, while 
Tripsacoid types with knobby chromosomes are most 
frequent in the lowlands. There is some indication that 
Tripsacoid maize can succeed and is to some extent re- 
placing non-Tripsacoid maize even at high altitudes. Of 
the sixty-eight varieties with six knobs or less, only two 
are found at an altitude lower than 6500 feet; while va- 
rieties with twelve knobs or more are frequently encoun- 
tered at approximately 5000 feet and occasionally at 6500 
feet and higher. 
The fact that non-Tripsacoid varieties of maize are 
found only at high altitudes in Guatemala is not neces- 
sarily in conflict with the assumption, previously men- 
{225 ] 
