1. Spikelets with 1 perfect terminal floret and a sterile or staminate floret below, 

 usually represented by a sterile lemma only, 1 glume sometimes 

 wanting; the rachilla articulated below the spikelets, the spikelets 

 thus falling entire (2) 



1. Spikelets 1- to many-flowered, the reduced florets (if any) above the perfect 



florets (except in Phalaris); the rachilla usually articulated above 

 the glumes (except in Leersia, Polypogon, Alopecurm, Spartino 

 and Agrostis semiverticillata) (16) 



2(1). Glumes membranaceous, the sterile lemma like the glumes in texture (3) 



2. Glumes indurate; fertile lemma and palea hyaline or membranaceous, the 



sterile lemma like the fertile one in texture (12) 



3(2). Spikelets subtended or surrounded by 1 to many distinct or more or less 

 connate bristles forming an involucre (4) 



3. Spikelets not subtended by bristles (5) 



4(3). Bristles persistent, the spikelets deciduous 55. Setaria 



4. Bristles falling with the spikelets at maturity 56. Cenchrus 



5(3). Glumes or sterile lemma awned (awn reduced to a point in Echinochloa 

 colonum) 54. Echinochloa 



5. Glumes and sterile lemma awnless (6) 



6(5). Fruit cartilaginous-indurate, flexible, usually dark-colored, the lemma with 

 more or less prominent white hyaline margins that are not inrolled 

 (7) 



6. Fruit chartaceous-indurate, rigid (8) 



7(6). Spikelets in slender racemes more or less digitate at the summit of the 

 culms 48. Digitaria 



7. Spikelets in panicles 47. Anthaenantia 



8(6). Spikelets placed with the back of the fruit turned away from the rachis 

 of the racemes, usually solitary (not in pairs) (9) 



8. Spikelets placed with the back of the fruit turned toward the rachis (first 



glume, when present, away from the rachis) of the spikelike ra- 

 cemes or pedicellate in panicles (10) 



9(8). First glume and the rachilla joint forming a swollen ringlike callus below 

 the spikelet 49. Eriochloa 



9. First glume present or wanting, not forming a ringlike callus below the spike- 



let 50. Axonopus 



10(8). First glume typically wanting; spikelets plano-convex, subsessile in spike- 

 like racemes 51 . Paspalum 



10. First glume present; spikelets usually in panicles (11) 



11(10). Second glume inflated-saccate, this and the sterile lemma much exceed- 

 ing the stipitate fruit 53 Sacciolepis 



11. Second glume not inflated-saccate 52. Panicum 



12(2). Spikelets unisexual, the pistillate below, the staminate above, in the same 

 inflorescence or in separate inflorescences 61. Tripsacum 



12. Spikelets in pairs, one sessile and perfect, the other pedicellate and usually 



staminate or neuter (the pedicellate one sometimes obsolete, rarely 

 both pedicellate); lemmas nyaline (13) 



13(12). Spikelets alike, all perfect 57. Erianthus 



13. Spikelets unlike, the sessile perfect, the pedicellate sterile (14) 



14(13). Pedicel thickened, appressed to the thickened rachis joint (at least 

 parallel to it) or adnate to it; spikelets awnless, appressed to the 

 joint 60. Manisuris 



170 



