Plant colors 
There is no reason to expect a relationship between 
knob numbers and the various plant colors; all are en- 
countered frequently in both Andean and Tripsacoid 
types of maize. No relationship was found between knob 
number and pericarp color, aleurone color or cob color, 
and the data are not included in Table II. Highly signi- 
ficant relationships were found, however, between knob 
number and endosperm color and knob number and pur- 
ple plant color. Varieties with yellow endosperm pre- 
dominate in the low-knob group, varieties with white 
endosperm in the high-knob group. What this means, 
if anything, in terms of Tripsacum contamination is diffi- 
cult to see. It might suggest that the greater the amount 
of Tripsacum admixture the more likely is the y allele 
from Tripsacum to be included, but this suggestion does 
not appear especially plausible when alleles involved in 
other plant colors are not so affected. Indeed in the case 
of purple plant color, the gene for which presumably de- 
rives from maize, the relationship is reversed. Here the 
proportion of purple plants is significantly greater in the 
high-knob than in the low-knob group even when allow- 
ance is made for the low frequency in which purple plants 
appear. he reason for the relationship between these 
two plant colors and knob number is not clear. 
Nature of the seminal root system 
Seedlings of Andean type maize and of the infrequent- 
ly knobbed Guarani maize of Paraguay are characterized 
by coarse, vigorous, primary and secondary seminal roots 
possessing a relatively small number of tertiary roots. 
Seedlings of Tripsacum, teosinte and strongly ‘Trip- 
sacoid maize have more fibrous root systems; the pri- 
mary roots are slender and thread-like, the tertiary 
roots abundant. The two extreme types of root systems 
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