we do not know, but if the plants were already monœcious before the change, and such a variation occurred, it would have been likely to have continued to exist in competition with the parent form on account of the greater chance for perfect fertilization of the silks.
The last step in our history is to make ancestral maize a perfect flowered species; that is, a form in which each flower has both male and female organs. There is no question but that this was once the case. "We know it by the characters possessed by the more ancient wild grasses and by the ease with which the plant reverts to the former condition. No one has isolated a race that breeds true to the older type, but every one who has raised corn has seen hundreds of tassels containing little seeds. It would seem that kindly external conditions alone are sufficient to bring back to the corn the memory of its old habit. When moisture is plentiful and the soil fertile, one can see these freaks by the hundreds in almost every field. The production of male flowers or their essential parts, the stamens, on the ears is much more rare, but it does occur.
Onr history is complete. We can picture to ourselves the wild promaize growing on the plateaus of Mexico and Central America thousands of years ago. A towering prince of grasses it was, bearing its tiny seeds on loose spikes at the ends of the branches. Conditions changed. The perfect flowers separated into two kinds, bearing organs of the different sexes. A type with shortened side branches appeared, giving the seeds greater protection from feathered and furry enemies. This was probably the grain that some wise man among the forerunners of the Toltecs discovered and made the foundation of American agriculture. From that time forth cultivation made possible the selection of variations that would not have survived in the wild. Variation must have been plentiful, and our aboriginal corn breeders less foolish in agriculture than they were in commerce, as is demonstrated by the numerous varieties improved by long selection presented to the white man in return for a few paltry beads of colored glass.