30 POACEAE 



34. TRISETUM Pers. False Oat. 



Inflorescence lanceolate, open; lower empty glume shorter than and scarcely more than 

 half as broad as the upper; leaf-blades broader than the sheaths and therefore 

 with auricles at the base. 

 Lemma about 7 mm. long; sheaths hairy. 1- T. canescens. 



Lemma about 5 mm. long ; sheaths glabrous. . , ,_ . 



Ovary pubescent at the apex; panicle loose; its branches spikelet-bearmg above 



the middle. 2. T. cernuum. 



Ovary glabrous; panicle denser; its branches spikelet-bearlng to the base. 



3. T. montanum. 

 Inflorescence dense,- oblong or oblong-lanceolate; lower empty glume nearly as broad as 



the upper; leaf-blades not broader than the sheaths, not aurlcled. 

 Leaf-sheaths and blades long-hairy ; upper part of the stem densely pubescent. 



4. T. subspicatum. 

 Leaf-sheaths and blades glabrous or the lowest sheath short-pubescent,, with reflexed 



hairs ; stem glabrous or slightly scabrous in the inflorescence. 5. T. majus. 



35. GRAPHEPHORUM Desv. 



Empty glumes nearly equal ; inflorescence narrow. 



Sheaths and upper surface of the leaves pubescent; spikelets 3-flowered. 



1. G. muticum. 

 Sheaths and leaves scabrous. 



Empty glumes barely equalling the lemma; spikelets 2-flowered; rudiment long- 

 hairy. 2. G. Wolfii. 

 Empty glumes longer than the lemma; spikelets 3-4-flowered; rudiment short- 

 hairy. 3. G. Brandegei. 

 Empty glumes unequal; inflorescence open. 4. G. Shearii. 



36. AVENA (Tourn.) L. Oats. 



Perennials, with rootstocks; empty glumes 5-12 mm. long; lemma hairy at the base. 

 Empty glumes shorter thaJi the flowers; panicle lax, narrow, and somewhat nodding; 



plant not tufted. 1. A. striata. 



Empty glumes longer than the flowers; panicle narrow and spike-like, strict; plant 

 tufted. 

 Plant 1-1.5 dm. high; leaves strongly involute; callus of the lemma and prolonga- 

 tion of the rachilla long-hairy. 2. A. Mortoniana. 

 Pleint 2-4 dm. high; leaves mostly flat; callus and rachilla short-hairy. 



3. A. Hookeri. 

 Annuals; panicle open; empty glumes over 2 cm. long; spikelets 2-4-flowered. 

 Lemma hairy, at least at the base; awn strongly twisted. 4. A. faiua. 



Lemma glabrous; awn scarcely twisted. 5. A: saliva. 



37. ARRHENATHERUM Beauv. Oat-grass. l. A. elatius. 



38. DANTHONIA DC. Wild Oat-grass. 



Lemma hairy on the back; inflorescence spike-like, with short, erect branches. 



Empty glumes 15-20 mm. long, long-acuminate. 1. D. Parryi. 



Empty glumes 8-13 mm. long, acute. 



Empty glumes 11-13 mm. long, conspicuously nerved, broad; teeth of the lemma 



subulate, 1-2 mm. long. 2. D. thermalis. 



Empty glumes 8-10 mm. long, narrow; teeth of the lemma ovate, often only 0.5 

 mm. long. 3. D. spicata. 



Lemma glabrous on the back. 



Empty glumes acute; inflorescence spike-like, with erect branches; stem-leaves erect. 



4. n. intermedia. 

 Empty glumes long-acuminate; inflorescence racemlform or spikelet solitary; stem- 

 leaves spreading or ascending. 



Lemma abruptly acuminate; spikelets usually 2-10, on spreading peduncles. 



5. D. californica. 

 Lemma not abruptly acuminate; spikelet usually solitary, if more than one, the 



peduncles erect. 6. 13. unispicata. 



39. SPARTINA Schreb. Mabsh-grass. 



First glume awn-pointed, equalling the lemma; second glume long-awned. 1. S. pectinata 

 First glume acute, shorter thaji the lemma; second glume acute. 2. S. gracilis. 



40. BECKMANNIA Host. Slough Grass. i. b. erucaeformis. 



41. SCHEDONNARDUS Steud. l. s. paniculatus. 



42. CHLORIS Sw. l. c. brevispica. 



43. BOUTELOUA Lag. Grama, Grama Grass, Mesquitb Grass, 



Buffalo Grass 

 Spikes 1-4. rarely more; spikelets 25 oi more. 

 Spikes usually more than one. 



Awns manifestly arising from between the lobes of the lemma; annual. 



1. B. polystachya. 

 Awns terminating the lobes of the lemma; cespitose tufted perennials. 



Stem densely villous below. 2. B. eriopoda. 



