324. WEATHERWAX: THE EVOLTUION OF MAIZE 
that is, the one terminating the main stem, to be male, and the 
lower ones, terminating the branches, to be female. Counts of 
male and female spikelets in a number of inflorescences showed in 
those of the main stem a ratio 
of 1 female to 18.5 male; in those 
of the primary branches the ratio 
was I to 7.5; and on secondary 
branches the ratio was. still 
higher. No unisexual inflores- 
cence has been observed, how- 
ever, on any plant. 
Male spikelets.\— The male 
spikelets are arranged on the 
rachis in two rows of pairs; and 
the male portion of the spike, 
even where there is but one spike 
in the inflorescence, has the same 
dorsoventral appearance as in 
maize or teosinte (FIG. 32); one 
Fic. 30. Habit of Tripsacum dactyloides. spikelet of a pair sometimes has 
usually sessile. 
a short pedicel, but both are 
The rachis of me male part of the spike becomes 
brittle soon after the pollen is shed. 
Fic, 31. 
Terminal inflorescence of Tripsacum dactyloides. 
The outer glume of the male spikelet is somewhat thickened 
and hardened, but otherwise the bracts, lodicules, stamens, and 
rudimentary pistils are essentially the same as those of maize or 
teosinte. 
