268 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Rachilla joint and first glume forming a swollen ringlike callus 

 at the base of the spikelet ; inflorescence paniculate. 



31. Eriocliloa (p. 298). 

 Rachilla joint and first glume not forming a callus at the base 

 of the spikelet ; inflorescence racemose. 

 Racemes racemose along the main axis ; first glume present. 



32. Brachiaria (p. 299). 

 Racemes aggregated at the summit of the culm ; first glume 



wanting 33. Axonopus (p. 299). 



Spikelets in 2's or 3's or solitary, placed with the back of the fruit 

 turned toward the rachis or pedicellate in panicles. 

 Fruit long-acuminate, scarcely indurate, both glumes wanting ; 

 spikelet sessile, solitary, the stiff racemes horizontal or 



reflexed at maturity 34. Reimarochloa (p. 302). 



Fruit not long-acuminate, indurate (if but slightly indurate both 

 glumes present). 

 First glume typically wanting ; spikelets plano-convex, sub- 

 sessile in spikelike racemes 35. Paspalum (p. 302). 



First glume present ; spikelets usually in panicles, biconvex to 



globose. 



Glumes or lemmas or both awned or, if short-pointed only, 



the summit of the fertile palea not inclosed and the 



spikelets crowded in short racemes. 



Inflorescence of 1-sided racemes along a common axis ; 



glumes 2-lobed (rarely entire), awned from between 



the lobes ; fruit indurate, the palea inclosed at the 



summit 43. Oplismenus (p. 343). 



Inflorescence paniculate. 



Spikelets long-silky ; first glume minute, remote. 



46. Tricholaena (p. 346). 

 Spikelets not silky, often scabrous or hispid. 

 Spikelets with a long-pointed callus at the base. 



45. Chaetium (p. 346). 



Spikelet without a callus 44. Echinochloa (p. 345). 



Glumes and lemmas awnless (fruit pointed in Scutachne). 

 Lower floret of the spikelet perfect, usually fruitful ; spike- 

 lets small, turgid, obtuse 42. Isachne (p. 341). 



Lower floret staminate or neuter. 



Second glume and sterile lemma leathery-indurate ; fruit 



mucronate 41. Scutachne (p. 341). 



Second glume and sterile lemma membranaceous ; fruit 

 not mucronate. 

 Inflorescence a cylindric or interrupted spikelike pani- 

 cle; fruit either scarcely indurate, the palea not 

 inclosed at the summit, or stipitate and the spike- 

 lets with a saccate second glume ; aquatics or sub- 

 aquatics. 

 Second glume inflated-saccate ; fruit stipitate. 



39. Sacciolepis (p. 339). 

 Second glume not inflated-saccate ; fruit scarcely 

 indurate, open at the summit, not stipitate. 



40. Hymenachne (p. 340). 



