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. CALAMAGBOSTIS. 



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. AGROSTIS. " 



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 Muhleribergia rcpcns) 17 



17a. Rachilla prolonged behind the palea; floret stipitate. 



73. BBACHYELYTETJM. 



17b. Rachilla not prolonged ; floret not stipitate 68. MUHLENBERGIA. 



16b. Lemma awnless or awned from the back 'i, 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. BLEPHARONEURON. 



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. SPOROBOLUS. 



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. 



TRIBE 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 



