Culms (1)2-4(6) m tall, (1)2-5 cm thick. Blades
50-90 cm long, 3-12 cm wide. Pistillate inflorescences spikes, 15-25(40)
cm long, 2-5(10) cm thick, cylindrical, tightly and permanently enclosed in
several to many leaf sheaths and a large prophyll, with 8-24 or more rows of
paired spikelets on a thickened, strongly vascularized, tough rachis (cob),
not disarticulating at maturity; fruitcases not developed, rachis internodes
fused into the extra-vascular cylinder, glumes reduced, shallow. Caryopses
60-1000+, exposed and naked. Staminate panicles with a polystichous central
axis and non-disarticulating branches; central axes usually much denser
and thicker than the usually distichous lateral branches, these lacking abscission
layers. 2n = 20.
Zea mays subsp. mays is the
familiar domesticated corn (or maize), from which around 400 indigenous races
and many different kinds of cultivars have been developed. It is an obligate
cultigen, unable to persist outside of cultivation because the caryopses are
permanently attached to the rachis and enclosed by the subtending leaf sheaths.
Supersweet cultivars have a double recessive gene that delays the conversion
of sugar to starch; flint corns have unusually hard endosperm; and waxy cultivars
have endosperm with an unusually high level of proteins and oils. Popcorns have
a core of soft, relatively moist endosperm surrounded by hard endosperm. The
grains pop when heat causes the moisture of the inner endosperm to vaporize.