7. Cenchrus. Spikelets (1–5) enclosed in a globular spiny bur-like involucre.
8. Amphicarpum. Spikelets of 2 kinds, one in a terminal panicle, the other subterranean on radical peduncles.
Tribe II. ORYZEÆ. Spikelets unisexual or perfect, in loose panicles, with only 2 glumes (in our genera) and palet none. Stamens often 6.
9. Leersia. Flowers perfect. Spikelets much flattened. Glumes carinate.
10. Zizania. Spikelets unisexual. Glumes convex, narrow.
Tribe III. MAYDEÆ. Spikelets of a single perfect or unisexual or rudimentary flower, in jointed spikes, in pairs at each joint, mostly imbedded in the thick rhachis.
11. Tripsacum. Spikelets monœcious, the staminate above in the spike.
12. Rottbœllia. One spikelet of each pair sterile and shortly pedicelled, the other fertile, sessile and sunk in the rhachis.
Tribe IV. ANDROPOGONEÆ. Spikelets in pairs or threes on the (usually jointed and bearded) rhachis of a spike or branches of a panicle, one sessile and fertile, the lateral pedicelled and often sterile or rudimentary; 2 upper glumes smaller and hyaline, that of the fertile flower mostly awned.
13. Erianthus. Spikelets in pairs, spicate, all alike fertile, involucrate with a silky tuft.