536 GR AMINES. (GRASS FAMILY.) 



flubtribe 2. AGROSTIDE^. Spikeleta 1-flowered, perfect, occasionally with the rndiment or 

 abortive pedicel of a second flower above, panicled, or the panicle sometimes contracted 

 into a cylindrical spike or head. Stamens 1-3. 



* PmEOiDKflS. Glumes equal, strongly keeled, laterally flattened, boat-shaped, somewhat her- 



baceous, as well as the paleae. Squamulae 2. Grain free. Inflorescence densely spiked. 

 8. ALOPECURUS. Glumes united at the base. Lower palea awned, the upper wanting. 

 4. PHLEUM. Glumes distinct. Palese 2, the lower truncate and awnless. 

 * TRUE AGROSTIDEJE. Glumes equal, or often unequal, concave or keeled, membranaceous. 

 Paleae membranaceous (except in part of No. 12). Squamulae 2. Grain free Inflorescence 

 panicled, open, or often contracted (glomerate), but not strictly spiked. 

 *- Glumes and paleae neither awned, bristle-bearing, nor mucronate, naked. Flower sessile in 



the glumes, naked at the base ; the lower palea 1-nerved. Fruit deciduous. 

 6. VILFA. Seed adherent to the closely investing pericarp, forming a caryopsis, or true grain, 

 as. in most Grasses. Panicle spiked or contracted 



6. SPOROBOLUS. Seed loose in the pericarp (utricle). Panicle spiked or diffuse. 



4- H- Glumes or the (3-6-nerved) lower palea awned, bristle-pointed, or mucronate (except in 

 eome species of Agrostis). Flower raised on a more or less evident stalk (callus) in the 

 glumes, naked, or barely hairy, at the base. 



7. AGROSTIS. Glumes equal, or the lower one rather longer, pointless, exceeding the very 



thin blunt paleae. Lower palea pointless, commonly awned on the back ; the upper 

 , sometimes wanting. Panicle open. 



8. POLYPOGON. Glumes nearly equal, long-awned, much longer than the paleae, the lower 



of which is often short-awned below the apex. Stamens 3. Panicle contracted. 



9. CINNA. Glumes acute, the lower about equalling, and the upper slightly exceeding, the 



similar paleae. Stamen 1. Paleae raised on a distinct naked stalk, beardless, the lower 

 one short-awned or bristle-pointed just below the tip ; the upper 1-nerved. 



10. MUHLENBERGIA. Lower glume mostly smaller. Paleae chiefly hairy-bearded at the 



base, the tip of the lower one mucronate-pointed or awned. Stamens 3. 



11. BRACHYELYTRUM. Lower glume nearly obsolete, and the upper minute. Lower paleae 



long-awned from the tip ; the upper grooved on the back and bearing a long and slen- 

 der naked pedicel of an abortive second flower. Stamens 2. 

 i- H- - Glumes and paleae not bristle-pointed. Flower hairy-tufted at the base. 



12. CALAMAGROSTIS. Lower palea mostly awned on the back, shorter than the glumes. 



* * * STIPES. Paleae coriaceous, or indurated in fruit, commonly shorter than the membra- 

 naceous glumes, on a rigid callus ; the lower involute, terete, closely enclosing the upper and 

 the grain, mostly 1 - 3-awned at the apex Squamulae mostly 3. Inflorescence racemose or 

 panicled : spikelets usually large, the flower deciduous from the persistent glumes. 



18. ORYZOPSIS. Awui simple, straight, deciduous from the palea, or sometimes wanting. 



14. STIPA. Awn simple, twisted below. Callus pointed at the base. 



16. ARISTIDA. Awn triple. Upper palea small. Callus pointed at the base 



* * * * Palea coriaceous or cartilaginous, awnless. Here the following would be sought by the 

 student who overlooked the pair of rudimentary flowers in No 55, and was not acquainted 

 with the recondite theoretical structure of No. 56 and 57. 



55. PHALARIS. Spikelets laterally flattened. A rudiment at the base of each palea. 



66. MILIUM. Spikelets dorsally flattish, not jointed with the pedicels : flowers all alike. 



67. AMPHICARPUM. Spikelets of two sorts, the fertile subterranean, those of the panieto 



separating by a joint without ripening grain. 



Subtribe 3. CHLORIDES. Spikelets (rarely 1-flowered, usually) 2 -several-flcwered, with one 

 or more of the upper flowers imperfect, disposed in one-sided spikes ! Glumes persist- 

 ent, the upper one looking outward Rhachis (axis) jointless. Spikes usually racemed 

 or digitate. Stamens 2 or 3. 



* Spikelets strictly 1-flowered. 



68. PASPALUM might be looked for here, having to all appearance merely 1-flowered spikelet* 

 16. SPARTINA. SpikeJets imbricated, 2-ranked, flat, crowded in alternate spikes. 



