The Manual of the Botany of the Northern United States / Including the District East of the Mississippi and North of North Carolina and Tennessee

by Asa Gray

19. Aristida. Awn 3-fid, the branches divaricate. Callus acute.

20. Stipa. Awn simple, twisted. Callus mostly acute.

21. Oryzopsis. Awn simple, straight, deciduous. Flower oblong; callus short, obtuse.

22. Milium. Awn none. Flower small, ovoid, without callus.

[+][+] Fruiting glume thin and membranous; outer glume smaller or minute.

23. Muhlenbergia. Flower mostly hairy at base, the glume mucronate or awned.

24. Brachyelytrum. Rhachis produced into a bristle above. Outer glumes very small, the flowering one long-awned. Stamens 2.

[*][*] Flowering glume awnless or short-awned, loosely embracing the grain, thin, the lower glumes complicate carinate; spikelets in dense spike-like panicles, the rhachis not produced.—Phleoideæ.

25. Heleochloa. Awns none. Spikes short and scarcely exserted.

26. Phleum. Glumes somewhat truncate, mucronate or short awned. Spike cylindric.