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. Eriochloa (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 spikeiike 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). 



