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 sShinince =e eee a ee 65. GASTRIDIUM. 
14b. Giumes not saceate at base; lemma awned or awnless; 
DANCES OPEN OI CONTA CEC Cee ee 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. CALAMAGROSTIS. 
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 
SU AIBN TT le ca 56. AGROSTIS. 
1ib. Glumes not longer than the lemma, usually shorter (the awn tips 
LOREM MULE OCTOLULTGAECENLOS W)) == ae eee ee 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. BRACHYELYTRUM. 
17b. Rachilla not prolonged; floret not stipitate___ 68. MUHLENBERGIA. 
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. 
Popes OFetsuwithOubt HainsTat ASCs a es es eae 20 
20a. Nerves of lemma densely silky________ 70. BLEPHARONEURON. 
20b: Nerves of Jemma not silkys2202 5.) tos ea 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 
DPEACES 22 Se lieth | eth Re eee aT 71. CrYpsis. 
22b. Inflorescence an open or contracted panicle. 
69. SPOROBOLUS. 
21b. Caryopsis not falling from the lemma and palea, 
remaining permanently inclosed in them; seed 
adnate’ toy the pericarpees ss. se ae ee 23 
23a. Panicles few-flowered, slender, rather loose; 
glumes minute, unequal, the first often want- 
ing; a low arctic alpine perennial__ 57. PHIPPsrA. 
23b. Panicle many-flowered, spikelike; glumes well 
developed, about-equalo--—==-- er ee 24 
24a. Panicle short, partly inclosed in the sheath ; 
low? aniniadl] 3° See ee eee 72. HELEOCHLOA, 
24b. Panicle elongate; perennial_____ 67. EXPICAMPES. 
Tribe 6, NAZTBAR. 
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 
