MANUAL OF THE GRASSES OF THE UNITED STATES 209 



Lateral nerves not excurrent. 



Spikelets not more than 5 mm long; lemmas 2 mm long. 



8. T. ERAGROSTOIDES. 



Spikelets 6 to 8 mm long; lemmas 4 to 5 mm long__5. T. btjckleyana. 

 Lateral nerves excurrent as short points. 



Rhizomes present, scaly and creeping 6. T. drummondii. 



Rhizomes wanting. 



Panicle 5 to 15 cm long; blades 1 to 3 mm wide 10. T. texana. 



Panicle 15 to 30 cm long, the branches viscid; blades 3 to 10 mm 



wide 9. T. flava. 



2b. Panicle narrow, contracted or spikelike, the branches appressed (see also 

 T. drummondii). 

 Panicle dense, oval or oblong, mostly less than 10 cm long. 



Lemmas deeply 2-lobed 2. T. grandiflora. 



Lemmas minutely notched, not lobed. 



Panicle 1 to 2 cm long; lemma margins densely long-ciliate; palea half 



as long as the lemma 3. T. pilosa. 



Panicle 4 to 10 cm long; lemma margins short-pilose near base; palea 



about as long as the lemma 4. T. congesta. 



Panicle slender, spikelike (long and dense in T. stricta). 



Lemmas glabrous. Panicle whitish 12. T. albescens. 



Lemmas pilose on the margins. 



Lemmas mucronate; panicle dense 11. T. stricta. 



Lemmas not mucronate (rarely lowest lemma obscurely so) ; panicle not 

 dense. 

 Glumes acuminate, longer than the lowest floret; blades mostly flat, 



some of them 2 to 4 mm wide 14. T. elongata. 



Glumes obtuse, short; blades mostly folded or involute, mostly about 

 1 mm wide 13. T. mutica. 



1. Triodia pulchella H.B.K. Fluffgrass. (Fig. 403.) Low, 

 tufted, usually not more than 15 cm high; culms slender, scabrous or 

 puberulent, consisting of 1 long internode, bearing at the top a 

 fascicle of narrow leaves, the fascicle finally bending over to the 

 ground, taking root and producing other culms, the fascicles also 

 producing the inflorescence; sheaths striate, papery-margined, pilose 

 at base; blades involute, short, scabrous, sharp-pointed; panicle 

 capitate, usually not exceeding the blades of the fascicle, consisting 

 of 1 to 5 nearly sessile relatively large white woolly spikelets; glumes 

 glabrous, subequal, broad, acuminate, awn-pointed, 6 to 8 mm long, 

 nearly as long as the spikelet; lemmas 4 mm long, conspicuously long- 

 pilose below, cleft about halfway, the awn scarcely exceeding the 

 obtuse lobes, divergent at maturity. % (Dasyochloa pulchella 

 Willd.; Tridens pulchellus Hitchc.) — Mesas and rocky hills, especially 

 in arid or semiarid regions, Texas to Nevada and southern California 

 to southern Mexico (fig. 404). 



2. Triodia grandiflora Vasey. Shortleaf triodia. (Fig. 405.) 

 Culms densely tufted, erect or geniculate below, 10 to 50 cm tall, 

 often pubescent at the nodes; blades flat or folded, rather firm, white- 

 margined, appressed-pubescent, 1 to 2 mm wide, those of the culm 

 less than 10 cm long; panicle dense, oblong, pale or sometimes pur- 

 plish, 2 to 6 cm long, cleistogamous spikelets borne in the lower 

 sheaths; spikelets 4- to 8-flowered, 5 to 12 mm long; glumes acuminate, 

 about as long as the first floret; lemmas 4 to 6 mm long, conspicuously 

 long-pilose on the margins, densely pilose on the back below, deeply 

 lobed, the awn as long as the lobes, or exceeding them. % — Rocky 

 slopes, western Texas to southern Arizona and northern Mexico. 

 This has been referred to T. avenacea H.B.K. , a Mexican species with 

 stolons and shorter purple panicles. 



