since a similar arrangement and shape occurs in ears from 
maize-teosinte crosses. Ears of Cuzco maize with more 
than the usual number of rows of grain often have iso- 
diametrical grains in a tesselated arrangement. If this 
had been the result of Tripsacum contamination, one 
would expect to find it in the ears with lower row num- 
bers instead of becoming more marked in the higher row 
numbers. Salpor of Guatemala and Cacahuatzintle of 
Mexico are similar to the many-rowed forms of Cuzco 
and occasionally have isodiametrical tesselate arranged 
grains. 
Kernel width divided by thickness gives a positive 
number which is an index to the grain cross section 
(Table I). Variations in grain size are common in some 
of the races studied and when prehistoric specimens and 
pop corns are compared with races described here, it may 
be noticed that, although there are often vast differences 
in the sizes of grains, there are similarities in the shapes. 
Colors have been used very little in this study for the 
examples found in most collections are the extremes. 
Colors are controlled by numerous factors which may 
interact, be modified or inhibited, be restricted in action 
to certain areas of the plant, or have a broad effect over 
nearly the entire plant. The most significant feature of 
colors in South American maize is the frequent occur- 
rence of browns and reds or purples. These colors are 
common in grasses. Brown grains are not only colored 
by a combination such as yellow or orange endosperm 
plus blue or purple pericarp, but by true brown pigments. 
The common maize of many districts is often divided 
into two types, a yellow and a white. This is true of the 
altiplano, where there is a flint with yellow endosperm 
and a white flour maize; of the valleys, where there are 
yellow and white forms of Cuzco; and of the Paraguay 
basin lowlands, where there is a flour maize with a yellow 
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