GR AMINES. 255 



+- +- +- +- Spikelets 3-flowered, the lateral reduced to a rudiment, the fertile coriaceous. 



12. Phalaris. Glumes boat-shaped. 



TRIBE III. POACE^E. Spikelet not articulated below the glumes, its rhachis articulated 

 above the glumes or continuous. Spikelets 1 - many-flowered. Lowest flower (with few 

 exceptions) perfect ; occasionally monoecious or dioecious ; terminal floret never more per- 

 fect than those below it. Axis of spikelet often terminated by an imperfect floret, which 

 is frequently reduced to a bristle or small point. 



Subtribe I. AGROSTIDE^E. Spikelets 1 -flowered, perfect, occasionally with a rudiment of 

 a second floret as an abortive pedicel. Callus, when manifest, often bearded. Awn, when 

 present, terminal or dorsal, not twisted. Lower palet usually thin. Inflorescence in open 

 panicles, or contracted and spike-like. 



* Callus not manifest ; floret sessile within the glumes. 

 +- Spikelets of two kinds, in pairs or threes. 



13. JEgopogon. One spikelet in a cluster perfect, the others staminate or neuter. 



+- +- Spikelets alike and perfect. 

 14 Coleanthus. Spikelets in small umbellate clusters. 



15. Vilfa. Spikelets in contracted panicles. Seed adherent to the pericarp (caryopsis). 



16. Sporobolus. Spikelets in usually open panicles. Seed free from pericarp (utricle). 



* * Callus present, the floret raised within the glumes on a short rounded or stalk-like base 



+- Glumes long-awned. 



17. Polypogon. Glumes much longer than the floret. 



+- +- Glumes awnless (except in one Agrostis). 



18. Agrostis. Lower glume slightly longer and exceeding the very thin blunt palets, the lower 



of which is 3-5-nerved and sometimes awned on the back, the upper often wanting. 



19. Gastridium. Glumes with a shining ventricose base. Inflorescence spike-like. 



20. Cinna. Lower glume shorter. Floret distinctly stipitate. Lower palet short-awned below 



the tip or awnless. 



21. Muhlenbergia. Glumes variable, sometimes minute. Lower palet awned from the apex. 



Floret mostly bearded at base and early deciduous, 

 -i- +- +- Glumes longer than the floret, which has a more or less conspicuous tuft of hairs at base. 



22. Vaseya. Awn terminal. No rudiment of a second flower. 



23. Calamagrostis. Awn from below the tip of palet. Rudiment present and mostly bearded. 



Subtribe II. STIPACE^E. Spikelets strictly 1 -flowered. Floret with a sharp-pointed callus, 

 deciduous. Lower palet involving the upper and the grain, coriaceous and indurated in 

 fruit and terminated by a (usually long) simple or triple awn. 



24. Eriocoma. Awn simple, short, angled, caducous. Floret clothed with long silky hairs. 



25. Btipa. Awn simple, long, twisted below. 



26. Aristida. Awn triple, continuous or (rarely) articulated with the palet. 



Subtribe III. CHLORIDES. Spikelets 1 - several-flowered (one or more of the upper florets 

 imperfect or rudimentary), in simple 1 -sided spikes upon a jointless rhachis; the spikes 

 racemed or digitate. 



* Spikelets 1 -flowered. 



27. Spartina. Spikelets much flattened laterally, in two rows upon one side of a 3-cornered 



rhachis. Spikes racemed. 



* * Spikelets 2-flowered or more, one floret perfect, with two or more imperfect or neutral flowers 



above it. 



28. Bouteloua. Lower palet 3-cleft and 3-awned at apex. Imperfect flowers often reduced to 



three awns. 



29. Cynodon. Floret and rudiment awnless. Spikelets in digitate spikes. 



* * * Spikelets 3 - several-flowered with more than one perfect floret. 



30. Leptochloa. Spikes slender, racemed. 



Subtribe IV. PAPPOPHORE^E. Spikelets 1 -many-flowered, perfect or staminate, in a 

 spike-like panicle. Glumes many- (3-9-) nerved, entire or 2-cleft, with the nerves often 

 excurrent as setae. Palets entire or 2-toothed, often awned. 



31. Pleuraphis. Spikelets in threes at each joint of the rhachis, subtended by a hairy tuft, 



the middle one perfect, the others staminate. 



Subtribe V. AVENACE^E. Spikelets panicled, 2 - several-flowered, the rhachis, often bearded, 

 prolonged into an imperfect rudiment. Glumes mostly equalling or exceeding the flowers. 



