16 FIELD COLUMBIAN MUSEUM BOTANY, VOL. III. 



Fruiting glumes indurated, empty glumes thin or membranaceous; 

 spikelets in racemes or panicles, falling from the continuous 

 rachis at maturity: 

 Spikelets perfect: 



Sunken in cavities of the broad flattened axis Stenotaphrum. 

 Not sunken in the axis: 



Subtended by an involucre of i to many bristles: 

 Spikelets falling, bristles persistent: 

 Empty glumes auricled and lyre shaped Set&riopsis. 

 Empty glumes not auricled nor lyre shaped Chcetochloa. 

 Bristles falling with the spikelets Cenchrus. 



Not subtended by bristles: 



Empty glumes awned Oplismenus. 



Empty glumes not awned: 



Floral glume auricled at base Ichnanthus. 



Floral glume not auricled at base: 

 Inrolled over the palea: 



Spikelets in unilateral racemes Paspalum. 



Spikelets (except Panicum paspal- ) Pani 



oides) not in unilateral racemes \ -. 

 Not inrolled Syntherisma. 



Spikelets monoecious, pistillate above, staminate / ^ , 



below in the same panicle \ 



Rachilla articulated above the empty glumes so that these remain after 



the fall of the fruiting glumes. Spikelets i to many flowered: 



Spikelets in 2 rows on I side of a continuous rachis forming unilateral 



spikes or racemes: 



With i perfect flower, often a staminate or neuter flower above it: 

 Awnless Cynodon. 



Awned: 



Spikes digitate at the summit of the culm Chloris. 

 Spikes racemed Bouteloua. 



Two to several flowered: 



Sessile, crowded in closely imbricated spikes: 

 Rachis with terminal spikelets Eleusine. 



Rachis extended in a naked point Dactyloctenium. 



Pediceled in spike-like racemes Leptochloa. 



Pediceled on one side of the branches of a \ ^ 



spreading panicle \ Comma. 



Spikelets not disposed in unilateral spikes, usually paniculate (soli- 

 tary or in pairs in Monanthochloe): 

 One-flowered: 



Floral glume indurated, awned Aristida. 



Floral glume thin membranaceous, awnless Sporobolus. 

 Two to many flowered: 

 Perfect: 

 Spikelets (except empty glumes) densely clothed with long 



hairs, equalling or exceeding the glumes: 

 Floral glume hairy, rachilla naked Arundo. 



Floral glume naked, rachilla hairy Phragmites. 



Spikelets glabrate or with short hairs only: 

 Floral glume bidentate, cuspidate Triodia. 



Floral glume entire, not cuspidate Eragrostis. 



Dioecious: 

 Spikelets solitary or in pairs, sessile in the I M hl 



axils of the rigid upper leaves \ 



Spikelets in contracted panicles Distichlis. 



Spikelets fascicled, cylindric, 3 or more cm. \ ua( f, a 

 long \ 



