WEATHERWAX: THE EVOLUTION OF MAIZE 325 
Female spikelets—The female portion of the spike (Fic. 32) 
is similar to that of teosinte, but there is usually more or less 
external evidence of dorsoventrality. The 
spikelets are alternately imbedded in alveoli in 
the rachis, forming two rows arranged almost 
symmetrically or along one side of the rachis. 
But the real four-rowed structure is clearly 
indicated, as in teosinte, by the presence of 
a rudimentary spikelet (Fics. 27, 28) near the 
base of each functional one. This rudiment 
is sometimes replaced by a functional spikelet, 
which may be either male or female (Fic. 
33). As in teosinte, the female portion of 
the spike easily separates at the nodes when 
the seeds are mature. 
The female spikelet has the same parts as 
that of teosinte, and they are arranged in the 
same way. The stigma is bipartite (Fics. 32, 
33), in contrast with that of Zea or Euchlaena. 
Seeds—The plants that I have grown 
ordinarily set seeds in only a few flowers, and 
these do not germinate well. Mr. Rodriguez 
has informed me that Tripsacum laxum, a solitary female spikelets. 
Central American species, has never been FS 33- Pair of female 
known to produce seeds. The morphological messin hokek 
basis of this peculiarity has not been deter- 
mined, but it is doubtless correlated with the perennial habit. 
SUMMARY OF MORPHOLOGY 
As is evident from the foregoing descriptions, these genera are 
identical in structural plan; for every significant organ in any one 
of them, there is a homologue, fully developed, rudimentary, or 
indicated, in each of the others. 
Common to all three is the jointed vegetative stem, bearing a 
leaf or a leaf rudiment at each node and a branch or a bud in the 
axil of almost every leaf. Buds, representing undeveloped shoots, 
bear no indication of giving rise to branches, because their nodes 
have ordinarily not developed far enough; but practically every 
fully developed node has a bud. 
