Despite some confusion over proper taxonomic groupings of the non-cultivated members of Zea, wild members maintain a successful array of annual or perennial plants with visible chromosomal peculiarities and ploidy levels, and many adaptive macroscopic phenotypes. Cultivated corn and the wild members of diploid and tetraploid Zea can be crossed to produce fertile F1 hybrids. The second major transformation of cultivated corn occurred in the United States in the twentieth century, and particularly since the 1930's. This transformation occurred through inbred lines for hybrid seed production, and by other methods. This transformation has resulted in more uniform commercial plants with superior agronomic characteristics, and has contributed to the six-fold increase in per acre yields in the last sixty years.
Pollen is produced entirely in the staminate inflorescences.
Eggs are produced entirely in the pistillate inflorescences. Corn styles and corn pollen tubes are the longest known in the plant kingdom. The staminate and pistillate inflorescences do not develop at the same time. The pistillate inflorescence is precocious. However, there is the appearance of slight protandry because the elongating styles are delayed for about seven days in emergence from the bracts of the pistillate inflorescence, while the development of the later-developing staminate inflorescence is fully visible.