POACEAE 143 



6. Tridens Drummdndii (Scribn. & Kearn. ) Nash. Stems 8-12 dm. tall from a 

 scaly rootstock, smooth : basal leaf-sheaths crowded, villous, the upper ones glabrous or 

 nearly so ; blades of the basal leaves elongated, 2-4 dm. long, about 5 mm. wide ; blade 

 of the uppermost stem-leaf 3 cm. long or less : panicle narrow, spike-like, 1.5-2 dm. long, 

 its branches short and appressed : spikelets rather loosely arranged, 3-5-flowered, 8-10 

 mm. long ; empty scales broad, 1-nerved, short-awned at the shortly 2-toothed apex ; 

 flowering scales firm, 5-6 mm. long, elliptic-ovate when spread out, their nerve-hairs about 

 0.8 mm. long, the apex 2-lobed, the nerves excurrent as projections. [ Triodia Drummondii 

 Scribn. & Kearn.] 



In dry soil or in low pine lands, South Carolina to Mississippi and Florida. Fall. 



7. Tridens sti ictus (Nutt.) Nash. Stems 5-15 dm. tall, smooth : leaf-sheaths smooth ; 

 blades erect or ascending, 4 dm. long or less, 2-7 mm. wide, long-acuminate, smooth ex- 

 cept on the margins : panicle narrow, spike-like, 1.5-3 dm. long, 1-1.5 cm. broad, its 

 branches short and appressed : spikelets crowded, 6-10-flowered, 5-6 mm. long ; empty 

 scales narrow, 1-nerved, acuminate, usually exceeding the flowering scales ; flowering 

 scales 3.5-4 mm. long, 1.5 mm. broad. and elliptic when spread out, their nerve-hairs about 

 0.8 mm. long, the lateral nerves usually slightly excurrent, the midnerve extended into a 

 short awn 0.25-0.5 mm. long. [ Triodia stricta (Nutt. ) Vasey.] 



In moist soil and meadows, Kansas to Mississippi and Texas. Summer and fall. 



8. Tridens cong6stus (L. H. Dewey) Nash. Stems tufted, 1-7 dm. tall, smooth : 

 leaf-sheaths shorter than the internodes, smooth ; blades ascending, 5-20 -cm. long, 2-5 

 mm. wide, long-acuminate, smooth beneath, roughish above : panicle dense, 3-8 cm. long, 

 1-1.5 cm. broad, its branches short and erect: spikelets nearly sessile, crowded, turgid, 

 8-15-flowered, 8-12 mm. long, about 4 mm. broad, ovate to oblong ; empty scales broad, 

 1-nerved, acute ; flowering scales about 5 mm. long, orbicular when spread out, their nerve- 

 hairs about 0.8 mm. long, the midnerve and often also the lateral nerves excurrent in short 

 projections; palet-nerves hispid and saccate at the base. [Triodia conyesta L. H. Dewey.] 



In dry soil, Texas. Spring to fall. 



9. Tridens muticus (Torr. ) Nash. Stems tufted, 2-5 dm. tall, roughened: leaf- 

 sheaths glabrous or papillose-hirsute ; blades erect or ascending, 2-12 cm. long, 3 mm. 

 wide or less, often involute when dry, rough : panicle narrow, 6-15 cm. long, its branches 

 appressed : spikelets 6-9-flowered, 10-12 mm. long, lanceolate ; empty scales 1-nerved ; 

 flowering scales 4-5 mm. long, obscurely and irregularly lobed at the obtuse or rounded 

 apex, the hairs on their margins and midnerve about 1.5 mm. long, the lateral nerves 

 vanishing below the apex, the midnerve also, or the latter continued to the apex, or rarely 

 excurrent as a short projection. [Tricuxpis mutica Torr.] 



On.dry hills, Texas to Arizona and northern Mexico. Spring to fall. 



10. Tridens elongatus (Buckl. ) Nash. Stems tufted, 3-9 dm. tall, very rough : leaf- 

 sheaths longer than the internodes, rough ; blades erect or ascending, 4-25 cm. long, 3 mm. 

 broad or less, long-acuminate, rough : panicle narrow, 12-25 cm. long, its branches ap- 

 pressed : spikelets 8-10-flowered, 10-14 mm. long, 3-4 mm. wide, elliptic ; first empty 

 scale 1-nerved, the second 3-5-nerved ; flowering scales 5-6 mm. long, the apex obtuse or 

 minutely 2-toothed, their hairs on the margins and midnerve about 1 mm. long, the lateral 

 nerves vanishing below the apex, the midnerve excurrent as a short projection. 



On plains or prairies, Colorado to Texas and Arizona. Summer and fall. 



11. Tridens Buckleyknus (Vasey) Nash. Stems 6-8 dm. tall, very rough, as are 

 the sheaths: leaf-blades 0.5-2 dm. long, 1-2.5 mm. wide, involute when dry, rough on 

 both surfaces : panicle narrow, slender, 1.5-2.5 dm. long, its main axis and appressed 

 branches rough, the larger ones 3-5 cm. long : spikelets loosely disposed, 3-5-flowered, 5-8 

 mm. long, 1.5-2 mm. wide, narrowly elliptic ; empty scales narrow, acuminate, the first 

 1-nerved, the second 3-nerved ; flowering scales about 5 mm. long, elliptic and about 2 mm. 

 wide when spread out, the apex minutely 2-toothed, the midnerve sometimes excurrent in 

 a short tip between the teeth, the lateral nerves vanishing just below the apex, the hairs on 

 the margins and midnerve scanty, about 0.4 mm. long. [Triodia Buckleyana Vasey.] 



In dry soil, southern Texas. Summer and fall. 



98. ERIONEURON Nash. 



Perennial tufted grasses, with thick linear leaf-blades having thickened white mar- 

 gins, and dense contracted almost capitate panicles. Spikelets several-many-flowered : 

 empty basal scales 2, narrow, acuminate : flowering scales broad, 3-nerved, pubescent on 

 the nerves below, and sometimes also on the body of the scale at the base, with long silky 



