Geographically the Maydeae are sharply divided into two groups, 
one in each hemisphere, and neither has ever made its way into 
the field of the other without the help of man. On the other hand, 
all the genera of each group overlap sufficiently in distribution to 
suggest an American progenitor and another in Australasia. 
Weatherwax might quite justifiably have emphasized 
even more than he did the close resemblance, morpho- 
logically, of maize to its two American relatives, teosinte 
and ‘Tripsacum. ‘True, its close relationship to teosinte 
may be of little significance if teosinte is, as has been 
suggested (Mangelsdorf and Reeves, 1939), a hybrid of 
maize and ‘T'ripsacum. But the resemblance of maize and 
Tripsacum, an indigenous American species which is 
widely distributed in both North and South America, 
is greater than is commonly recognized and is certainly 
highly significant. In both genera one floret in each pis- 
tillate spikelet is suppressed and in both it is the lower 
floret which undergoes such suppression. In both genera 
the caryopsis is either enclosed, or surrounded at the 
base, by a structure which is made up of a segment of 
the rachis containing an alveolus, and the glumes. In 
Tripsacum the glumes are indurated while in maize they 
are often membranous or fleshy, but there is evidence 
from maize-teosinte crosses that this difference is in some 
cases a simple Mendelian one of the same general mag- 
nitude as that which distinguishes sweet corn from field 
corn. Maize normally bears paired pistillate spikelets and 
Tripsacum solitary ones, but paired spikelets have been 
observed in Tripsacum by Dr. Cutler and solitary spike- 
lets in maize by Hepperly (1949), so that discontinuity 
between the two plants in these characters is not com- 
plete. Maize is an annual and Tripsacum a perennial 
possessing several characters normally associated with the 
perennial habit. The distinction is not of profound im- 
portance since annual and perennial species are some- 
times found within the same genus. The resemblance to 
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