104 



CONTEIBUTIONS FROM THE NATIONAL HEEBAEIUM. 



69. PUCCINELLIA Pari. ]\Ieadow grass. 



Cespitose perennial with flat leaves and naiTow terminal panicles; spikelets as in 

 Panicularia but with usually smaller lemmas, the nerves less distinct or obscure. 



1. Puccinellia airoides (Nutt.) Wats. & Coult. in A. Gray, Man. ed. 6. 668. 1890. 



Poa airoides Nutt. Gen. PI. 1: 68. 1818. 



Panicularia distans airoides Scribn. Mem. Torrey Club 5: 54. 1894. 



Type locality: "In depressed situations around the Mandan village, on the 

 Missouri." 



Range: British America to Nevada and New Mexico. 



New Mexico: Shiprock; Farmiagton; Arroyo Pecos near Las Vegab. Wet ground, 

 in the Upper Sonoran Zone. 



70. AGROPYRON Gaertn. Wheat grass. 



Tall perennials with erect simple culms and often bearded terminal spikes; spike- 

 lets 3 to many-flowered, closely sessile and single at each notch of the axis; rachilla 

 articulated above the glumes under each lemma; glumes 2, narrower and usually 

 shorter than the lemmas, acute or awned; lemmas rounded on the back or slightly 

 keeled above, 5 to 7-nerved, acute or awned from the apex, rarely obtuse; palea 2- 

 keeled, bristly-ciliate on the keels; grain pubescent at the apex, usually adherent to 

 the palea. 



KEY TO THE SPECIES. 



Rachis of the spike breaking up at maturity, the joints falling 



with the spikelets 1. A. scribneri. 



Rachis of the spike continuous, not breaking up at maturity. 

 Awns of the lemmas conspicuous. 

 Awns erect. 



Awns short, not exceeding the body of the lemma; 



spikes usually tinged with purple 2. A. violaceum. 



Awns long, usually exceeding the body of the 

 lemma; spikes not purplish tinged. 

 Stems stout; spikes 7 to 10 mm. wide, usually 

 unilateral; spikelets (excluding the awns) 



12 to 15 mm. long 3. A. richardsoni. 



Stems slender; spikes about 5 mm. wide, seldom 

 unilateral ; spikelets (excluding the awns) 



about 10 mm. long 4. A. caninum. 



Awns divergent. 



Spikelets sub terete, more or less crowded 5. A. bakeri. 



Spikelets flattened, distant. 



• Leaves scabrous above 6. A. arizonicum. 



Leaves glabrous 7. A. spicatum. 



Awns of the lemmas not conspicuous. 

 Plants bright green, not glaucous. 



Plants cespitose; spikelets small, few-flowered 8. A. tenerum. 



Plants stoloniferous; spikelets large, many-flowered. 9. A. pseudorepens. 

 Plants conspicuously glaucous. 



Sheaths pubescent 10. A. palmeri. 



Sheaths glabrous. 



Lemmas scabrous or glabrous 11. A. smithii. 



Lemmas pubescent 12. A. violle. 



