312 WEATHERWAX: THE EVOLUTION OF MAIZE 
are all native of southeastern Asia and the neighboring islands. 
An anomalous American genus, Pariana, has been included in 
this tribe by some authorities, but its natural position seems to be 
in another group. 
The best evidences concerning the immediate ancestry of 
maize come from a comparative study of the three American 
genera of the Maydeae. The Asiatic species are probably much 
_ t. A variety of corn from an 
servation; this plant may be con- 
ad ihe type of the species, which is to- 
day essentially the same as when first seen 
by the white man. 
less closely related to those of 
America than they are to each 
other; and, for present pur- 
poses, they will not be con- 
sidered in detail. 
Zea and Euchlaena are suf- 
ficiently closely related to 
cross readily, and there is a 
record of at least one case of * 
hybridization of Euchlaena 
and Tripsacum; but I have 
found no record of any hybrid 
between Zea and Tripsacum. 
MorpHoLocy OF ZEA 
The genus Zea, represented 
by the single species, Zea 
Mays L., comprises all the 
varieties of maize. Being the 
Maydeae, it is taken as the 
basis for comparison. It isa 
very variable species, but its 
variability is mostly quanti- 
tative in character. Good 
general descriptions of the 
plant have been available for 
a long time, but some sig- 
sifrant details have not thus far been included in any of these. 
A complete working description makes necessary here the repe- 
tition of some well-known facts as a proper background for new 
details. 
