POACEAE 129 



70. 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 pro- 

 longed beyond the flowers. Scales 4, the 2 outer empty, persistent, keeled, acute, mem- 

 branous, 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. caespitoxa. 



Flowering scales about 4 mm. long, acute or obtuse : leaf-blades involute. 2. D. flexuosa. 



1. Deschampsia caespitosa (L. ) Beauv. Stems tufted, 6-12 dm. tall, erect: leaf- 

 blades flat, 2-3 mm. wide, rough above, the basal ones numerous, J-J as long as the stem, 

 those on the stem 5-15 cm. long : panicle open, 7-23 cm. long, its branches spreading or 

 ascending, 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. 



In wet soil, Newfoundland to Alaska, New Jersey, Illinois, Minnesota and in the mountains to 

 North Carolina, New Mexico and California. Also in Europe and Asia. Summer. 



2. Deschampsia flexuosa ( L. ) Trin. Stems tufted, 3-8 dm. tall, erect, slender : 

 leaf-blades involute-setaceous, rough above, the basal very numerous, | as long as the stem 

 or less, those on the stem 2-8 cm. long : panicle open, 5-20 cm. long, the branches spread- 

 ing to nearly erect, naked at the base, 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 ex- 

 ceeding the scale. 



In dry soil, Greenland and Newfoundland to Ontario, Michigan, North Carolina and Tennessee. 

 Also in Europe. Summer. 



71. TRISETUM Pers. 



Annual or perennial tufted grasses, with flat leaf-blades and terminal spike-like con- 

 tracted 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, membranous, 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 flowering 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. FALSE OAT. 



Flowering scales each bearing a long awn. 



Empty scales shining, 1-nerved, or the second one 3-nerved. 



Panicle spike-like, dense, its branches short and appressed. 1. T. subspicatum. 



Panicle loose and open, its branches long and slender, erect or ascending. 2. T. flavcscens. 

 Empty scales not shining, very strongly nerved, the first 3-nerved, the second 



5-nerved. 

 Awn of the flowering scales inserted about % way below the apex : teeth 



of the flowering scales cuneate. 3. T. Hallii. 



Awn of the flowering scales inserted about the middle : teeth of the flower- 

 ing scales subulate. 4. T. interruptum. 

 Lower flowering scale not bearing a long awn, a remnant sometimes'present. 

 Second empty scale less than 3 mm. long : awn of the flowering scales 1-2 mm. 



long. 5. T. aristatum. 



Second empty scale 4-5 mm. long : awn of the flowering scales exceeding 3 



mm. in length. 

 Empty scales dissimilar, the first much narrower than the second, 1-nerved, 



or sometimes 3-nerved at the base : leaf-blades 1 dm. long or less. 6. T. Pennsylvaniciim. 



Empty scales similar, the first about as broad as the second, strongly 3- 



nerved : leaf-blades 1.5-2 dm. long. 7. T. Ludovicianum. 



1. Trisetum subspicatum (L. ) Beauv. Softly pubescent or glabrous in some or all 

 of its parts. Stems 1-6 dm. tall, erect : leaf-blades 2-10 cm. long, 1-4 mm. wide : pan- 

 icle spike-like, 2-13 cm. long, oval to oblong, sometimes interrupted below : spikelets 2-3- 

 flowered, the empty scales hispidulous on the keel, the second one about 5 mm. long, the 

 flowering scales 4-5 mm. long, acuminate, hispidulous, each bearing a long bent and some- 

 what twisted awn. [ T. molle Kunth. ] 



In dry or rocky places, Labrador to Alaska, and in the mountains to North Carolina, New Mexico 

 and California. Also in Europe and Asia. Summer and fall. 



2. Trisetum flavescens ( L. ) K. & S. - Stems 4-8 dm. tall, erect, glabrous : leaf- 

 sheaths pubescent ; blades 4-13 cm. long, 2-6 mm. wide, rough : panicle open, 5-13 cm. 



