46 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Lemmas pilose on the nerves 31. Blepharoneuron (p. 74). 



Lemmas not pilose on the nerves. 

 Lemmas 1-nerved; pericarp sep- 

 arating from the seed 32. Sporobolus (p. 75). 



Lemmas 3 to 5-nerved; peri- 

 carp adherent to the seed. 

 Rachilla prolonged behind 

 the palea; lemma 

 with a short awn on 



the back 36. Calamagrostis (p. 79). 



Rachilla not prolonged be- 

 hind the palea; lem- 

 mas awn less. 

 Glumes longer than the 



floret 37. Oalamovilfa (p. 80). 



Glumes shorter than the 



floret 35. Agrostis (p. 78). 



Tribe VII. AVENEAE. 



Awns attached between the teeth of the lemma, flat- 

 tened 38. Danthonia (p. 80). 



Awn a dorsal, not flattened. 



Grain adherent to the palea; spikelets mostly 



more than 10 mm. long 39. Avena (p. 81). 



Grain free; spikelets less than 10 mm. long. 



Lemmas erose or shortly 2-lobed at the apex; 



panicles open 40. Deschampsia (p. 81). 



Lemmas deeply 2-toothed at the apex, the 

 teeth awn -pointed; panicles dense and 

 congested 41. Trisetum (p. 82). 



Tribe Vm. CHLORIDE AE. 



Spikelets unisexual, dissimilar; flowers monoecious or 



dioecious 42. Bulbilis (p. 82). 



Spikelets all alike. 



Spikelets with 2 to 4 perfect flowers. 



Spikelets small, numerous, approximate; 



glumes thin 43. Leptochloa (p. 83). 



Spikelets large, few, distant; glumes firm 



and thick 44. Acamptoclados (p. 84). 



Spikelets with 1, rarely 2, perfect flowers. 



[Rachilla jointed below the boat-shaped in- 

 flated glumes, the whole spikelet fall- 

 ing at maturity 45. Beckmannia (p. 84). 



Rachilla jointed above the glumes, these per- 

 sistent, not boat-shaped. 

 No sterile lemmas present above the 

 perfect floret. 

 Plants with long stolons; spikelets 

 numerous, crowded; spikes 2 

 to 6, digitate 46. Capriola (p. 84). 



