POACEAE. 27 



1. N. lanatus (L.) Nash. Softly and densely pubescent. Stems 4-9 dm. tall: 

 leaf -blades 2.5-15 cm. long, 4-12 mm. wide: spikelets 4 mm. long; the upper one 

 awn-pointed, the flowering scales 2 mm. long, glabrous, shining, the upper one 

 2-toothed and bearing a finally hooked awn just below the apex. — Common, 

 in moist fields and meadows. Nat. of Eu. — Sum. — Velvet-grass. 



28. DESCHAMPSIA Beauv. Perennial grasses, with narrow convolute 

 or flat leaf-blades and terminal contracted or open panicles. Spikelets 2- 

 flowered, the rachilla articulated above the empty scales and prolonged beyond 

 the flowers. Scales 4, the 2 outer empty, persistent, keeled, acute, membranous, 

 usually somewhat shining, the flowering scales thin-membranous, almost hyaline, 

 entire or toothed, acute, obtuse, or truncate and denticulate at the apex, each 

 bearing a slender dorsal straight or geniculate awn which is twisted at the 

 base; palet narrow, 2-nerved. Stamens 3. Styles distinct. Stigmas plumose. 

 — • Hair-grass. 



Flowering scales about 2.5 mm. long, erose-truncate : leaf-blades flat. 



1. D. caespitosa. 

 Flowering scales about 4 mm. long, acute or obtuse : leaf-blades 



involute. 2. D. flexuosa. 



1. D. caespitosa (L.) Beauv. Stems 6-12 dm. tall: leaf-blades 2-3 mm. wide, 

 the basal ones numerous, those on the stem 5-15 cm. long: panicle open, 7-23 

 cm. long, naked at the base: spikelets 3.5-4 mm. long, the flowering scales 

 about 2.5 mm. long, erose-truncate at the apex, the awns somewhat shorter or 

 a little longer than the scale. — M. S, Eare, in swamps. — Limestones, 

 schists. — • Sum. 



2. D. flexuosa (L.) Trin. Stems 3-8 dm. tall: leaf -blades involute-setaceous, 

 the basal very numerous: panicle open, 5-20 cm. long, flexuous: spikelets 4.5-5 

 mm. long, the flowering scales about 4 mm. long, acutely toothed at the apex, 

 the awns bent and twisted, much exceeding the scale. — Susquehanna valley. 

 Common, on dry or rocky hills. — Limestones, schists. — Sum. 



29. TRISETUM Pers. Annual or perennial tufted grasses, with flat leaf- 

 blades and terminal spike-like contracted or open panicles. Spikelets usually 

 2-flowered, rarely 3-6-flowered, the flowers perfect, or the upper one staminate, 

 the rachilla glabrous or pilose, articulated between the flowering scales and 

 prolonged beyond them. Scales 4, rarely 5-8, keeled, the 2 outer empty, membra- 

 nous, unequal, acute, entire at the apex, awnless, persistent, the flowering scales 

 usually shorter, sometimes longer, 2-toothed at the apex, the teeth acuminate 

 and often terminating in a bristle or slender awn, awned, or the lower flower- 

 ing scale rarely awnless, the awn often twisted, inserted below the apex and 

 arising between the teeth; palet hyaline, 2-toothed. Stamens 3. Styles distinct. 

 Stigmas plumose. 



1. T. pennsylvanicum (L.) B.S.P. Stems 3-9 dm. tall: leaf-blades 1 dm. long 

 or less, 1-4 mm. wide: panicle 6-15 cm. long, its branches erect or ascending: 

 spikelets of four scales, the empty ones about equal, the flowering scales 4-5 

 mm. long, the second one hispidulous or nearly glabrous. — M. S. Rather rare, 

 in swamps and wet places. — Limestones, schists. — Sum. 



30. AVENA [Tourn.] L. Annual or perennial grasses, varying in habit, 

 with usually flat leaf -blades and terminal contracted or open panicles. Spikelets 

 generally large, erect or pendulous, usually 2-several-flowered, rarely 1-flowered, 

 the rachilla articulated between the fertile flowers, the lower flowers perfect, 



