GENERA OF GRASSES OF THE UNITED STATES. 
15 
Key to the genera of Agrostideae — Continued. 
14a. Glumes saccate at base ; lemma long-awned ; inflorescence 
contracted, shining 65. Gasteidium. 
14b. Glumes not saccate at base ; lemma awned or awnless ; 
panicles open or contracted 15 
15a. Florets bearing a tuft of hairs at the base from the 
short callus, the hairs at least half as long as the 
lemma ; palea present 53. Calamageostis. 
15b. Florets without hairs at the base or with short 
hairs rarely as much as half the length of the 
lemma (Agrostis hallii) ; palea usually small or 
wanting 56. Ageostis. 
lib. Glumes not longer than the lemma, usually shorter (the awn tips 
longer in Muhlenbergia racemosa) 16 
16a. Lemma awned from the tip or mucronate, 3 to 5 nerved (lateral 
nerves obsolete in Muhlenbergia repens) 17 
17a. Rachilla prolonged behind the palea; floret stipitate. 
73. Beachyelytetjm. 
17b. Rachilla not prolonged ; floret not stipitate 68. Muhlenbeegia. 
16b. Lemma awnless or awned from the back 18 
18a. Florets bearing a tuft of hairs at the base from the short 
callus; lemma and palea chartaceous, awnless 19 
19a. Panicles spikelike ; rachilla prolonged 54. Ammophila. 
19b. Panicles open ; rachilla not prolonged 55. Calamovilfa. 
18b. Florets without hairs at base 20 
20a. Nerves of lemma densely silky 70. Blephaeoneueon. 
20b. Nerves of lemma not silky 21 
21a. Caryopsis at maturity falling from the lemma and 
palea ; seed loose in the pericarp, this usually 
opening when ripe; lemma 1-nerved 22 
22a. Inflorescence capitate in the axils of broad 
bracts 71. Crypsis. 
22b. Inflorescence an open or contracted panicle. 
69. Spoeobolxjs. 
21b. Caryopsis not falling from the lemma and palea, 
remaining permanently inclosed in them; seed 
adnate to the pericarp 23 
23a. Panicles few-flowered, slender, rather loose; 
glumes minute, unequal, the first often want- 
ing; a low arctic alpine perennial— 57. Phippsia. 
23b. Panicle many-flowered, spikelike; glumes well 
developed, about equal 24 
24a. Panicle short, partly inclosed in the sheath ; 
low annual 72. Heleochloa. 
24b. Panicle elongate; perennial 67. Epicampes. 
Teibe 6, Nazieae. 
Spikelets subsessile in short spikes of 2 to 5 (single in Oster- 
damia), each spike falling entire from the continuous axis, usually 
1-flowered, all perfect, or perfect and staminate together in the same 
spike; glumes usually firmer than the lemma and palea, sometimes 
awned, the lemma awnless. 
This small and unimportant tribe is known also as Zoysieae. In 
Osterdamia the spikelets are single and have only one glume, this 
