50 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Tribe II. AGBOSTIDEAE. 



Lemmas awned or mucronate-pointed . 

 Awn terminal. 



Awn much exceeding and articulated with the lemma. 2. Stipa. 



Awn very short, not articulated with the lemma 7. Cinna. 



Awn dorsal. 



Rachilla prolonged behind the palea into a slender, 

 usually plumose or hairy bristle. 

 Awn very minute, attached near the apex of the 



lemma 9. PODAGROSTIS. 



Awn longer, attached at or below the middle of 



the lemma 10. Calamagkostis. 



Rachilla not prolonged behind the palea. 



Inflorescence an open panicle 8. .Agrostis. 



Inflorescence a dense cylindrical spike-like panicle. 4. Alopecurith. 

 Lemmas awnless. 



Rachilla prolonged behind the palea into a short, naked 



bristle (>■ Arctagrostis. 



Rachilla not prolonged behind the palea. 

 Lemmas mostly shorter than the glumes. 



Glumes abruptly awn-pointed ; inflorescence a 



dense cylindrical panicle 3. Phleum . 



Glumes acute; inflorescence not in dense cylin- 

 drical panicles S. Agrostis. 



Lemmas much exceeding the minute flumes 5. Phippsia. 



Tribe III. AVENEAE. 



Lemmas awned from below the middle II. Deschampsia. 



Lemmas awned from above the middle. 



Rachilla prolonged as a sterile pedicel, lemma bearing a 



dorsal, twisted awn 12. Trisetum. 



Rachilla not prolonged, lemma bearing a straight awn just 

 below the apex 13. Avena. 



Tribe IV. CHLOEIDEAE. 



Spikelets sessile, closely imbricated in two rows along the short 

 branches of the panicle, the glumes equal, inflated, and 

 rounded on the back 14. Beckmannia. 



Tribe V. FESTTJCEAE. 



Lemmas 1 to 3-nerved or nerveless. 



Callus or base of the lemma hairy or barbate; glumes gla- 

 brous, acute 19. Colpodium. 



Callus and base of the lemma glabrous; glumes obtuse, 



scarious 15. Catabrosa. 



