on the margin between the lowlands and the highlands, 
and not far from the separation of the Amazon and Para- 
guay River basins. 
The most peculiar characteristic of Coroico maize 
(Plate XXXV, A, B) is the arrangement of the ali- 
coles which has been described on page 272. The long, 
slender and flexible ears have a light brown cob with very 
little pith and the shallow alveoles and slender pedestals 
do not stiffen the ears like the trusswork system of deep 
alveoles with the horny attached glumes of North Amer- 
ican and most South American cobs. The isodiametrical 
grains are nearly always brown-orange in color due to the 
presence either of the brown aleurone characteristic of 
Guarani maize or to a brown-orange aleurone hitherto 
unknown to students of maize. The presence of a dom- 
inant inhibitor for other aleurone colors makes grains of 
any color except brown-orange infrequent in this race. 
The plant of Coroico maize is as distinct from the 
other races of South America as is the ear. When grown 
in Cochabamba it tillers abundantly and has narrow 
leaves with a distinct hairy channel over the midrib. 
All of the leaf sheaths have hairs which are stiffer and 
straighter than those found in the pubescent types of 
Central America. 
Guarani maize 
This is the maize grown throughout most of the low- 
lands and plains of the Paraguay River basin, an area 
inhabited mainly by the Guarani Indians and related 
groups. The ears (Plate XX XV, C, D) usually have 12 
or 14 rows of grains, are of good size, nearly cylindri- 
cal, with the naked cob protruding beyond the grains as 
in Tripsacoid types. The number of chromosome knobs 
in the plants Mangelsdorf studied was extremely low 
and some plants had no knobs. Although the cobs are 
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