624 GRAMINE^E. (GRASS FAMILY.) 



Tribe III. MAYDEJE. 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 monoecious, the staminate above in the spike. 



12. Kottboellia. One spikelet of each pair sterile and shortly pedicelled, the other fertile, 



sessile and sunk in the rhachis. 



Tribe IV. ANDROPOGONE3. 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 lat- 

 eral 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. 



14. Andropogon. Spikelets spicate, in pairs, the pedicellate sterile or rudimentary; 



rhachis bearded. 



15. Chrysopogon. Spikelets in open panicles, in pairs or threes, only the sessile fertile. 



SERIES B. Rhachis of the spikelet usually jointed above the persistent lower 

 glumes (jointed below the glumes only in n. 19, 31, and 36). Spikelets 

 1 - many-flowered, the uppermost flowers often imperfect or rudimentary. 



Tribe V. PHAIjARIDE^E. Glumes 5, only the uppermost fertile, the 2 middle ones 

 rudimentary or empty or staminate ; palet 1-nerved. Panicle mostly contracted and 

 spike-like. 



16. Phalaris. Middle glumes mere rudiments each side of the shining triandrous flower. 

 17 Antb.oxantb.um. Middle glumes empty, awned on the back. Stamens 2. 



18. Hierochloe. Middle glumes triandrous. Fertile flower diandrous. 



Tribe VI. AGROSTIDE^]. Glumes 3 ; flower solitary, perfect (rarely a rudimentary 

 or perfect second flower in n. 23 and 32 - 34) ; palet 2-nerved. 



* Flowering glume with a terminal awn (none in n. 22), closely embracing the grain in fruit , 



spikelets in panicles or loose spikes, the rhachis not produced beyond the flower (except 

 in n. 24 and a single species of n. 23). STIPES. 



*- Fruiting glume firm and indurated, with a callus at base (none in n. 22). 



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



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



21. Ory/opsis. Awn simple, straight, deciduous. Flower oblong ; callus short, obtuse. 



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



- f- 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 pro- 

 duced. PHLEOIDE JR. 



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



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



27. Alopecurus. Lower glumes united at base, the flowering awned on the back. Palet 



none. Spike cylindric. 



* * * Glumes membranous, the lower rarely strongly complicate, the flowering with a dor 



sal awn or awnless ; spikelets variously panicled. AGBOSTE^;. 

 - Flowering glume 1- (rarely 3-) nerved, awnless ; grain loosely enclosed or naked. 



28. Sporobolus* Culms wiry or rigid. Leaves involute. 



- - Flowering glume 3 - 5-nerved, mostly awned ; grain enclosed. 

 M- Rhachis not -reduced above the single flower. 



29. Agrostis. Spikelets in an open panicle. 



30. Polypogon. Empty glumes long-awned. Panicle spike-like. 



31. Cinna. Spikelets flattened, in a loose panicle. Palet 1-nerved, Stamen 1. 



