130 POACEAE 
long, its branches ascending or erect, somewhat flexuous, naked below : spikelets 3—4- 
flowered, the first empty scale about 4 as long as the second which is about 5 mm. long, the 
flowering scales 5-6 mm. long, hispidulous, each bearing a long, bent and twisted awn. 
In waste places and fields, Missouri, Kansas and Mississippi. Naturalized from Europe or Asia. 
Summer. 
3. Trisetum Hállii Scribn. Stems tufted, 1.5-5 dm. tall, slender: leaf-blades 3-13 
em. long, 2-3 mm. wide, rough, flat, or somewhat involute: panicle contracted, 3-15 em. 
long, its branches erect or nearly so: spikelets 4—5 mm. long, exclusive of the awns, the 
first scale much narrower and almost as long as the second. 
On prairies, Texas. Spring. 
4. Trisetum interrüáptum Buckl. Stems tufted, 5 dm. tall or less, slender: leaf- 
sheaths glabrous or pubescent ; blades flat or involute, rough, 8 em. long or less, 1-2 mm. 
wide: panicle 4-13 em. long, its branches erect or nearly so: spikelets 4-5 mm. long, ex- 
clusive of the awns, the first scale narrower than the second but about as long. 
In dry soil, Texas. Spring. 
5. Trisetum aristàtum (Scribn. & Mer.) Nash. Stems 4-6 dm. tall, erect, slen- 
der: leaf-blades 1.5 dm. long or less, 1-2 mm. wide, roughish : panicle slender, 1.5-2.5 
dm. long, its branches erect or nearly so, the larger ones 6-8 em. long : spikelets of 4 or 5 
scales, 4.5-5 mm. long, exclusive of the awns, the first scale linear, several times narrower 
than the broad second scale. 
In moist or dry soil, North Carolina. Summer. 
6. Trisetum Pennsylvánicum (L.) B.S.P. Stems 3-9 dm. tall, erect, slender and 
often weak: leaf-sheaths sometimes rough; blades 1 dm. long or less, 1-4 mm. wide, 
rough : panicle 6-15 em. long, its branches erect or ascending: spikelets of four scales, 
the empty ones about equal, the first a little shorter than the second, the flowering scales 
4-5 mm. long, the second one hispidulous or nearly glabrous. [7 palustre Torr. ] 
In swamps and wet meadows, New York to Virginia, Tennessee and Florida. Spring and summer: 
7. Trisetum Ludoviciànum Vasey. Stems 6-9 dm. long, weak : leaf-blades flat, the 
larger ones 1.5-2 dm. long, 4-6 mm. wide, rough : panicle 1.5-2.5 dm. long, its branches 
erect or nearly so: spikelets usually of 4 scales, the first a little shorter than the second, 
the second flowering scale strongly hispidulous. 
In wet places, Louisiana. Spring. 
72. AVENA L. 
Annual or perennial grasses, varying in habit, with usually flat leat-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, the upper ones often staminate or wanting. Scales 4-several, rarely 
3, the 2 outer empty, membranous, exceeding or shorter than the flowering scales, persist- 
ent; the flowering scales 5-9-nerved, rounded on the back, the apex frequently shortly 2- 
toothed, the scales enclosing perfect flowers and bearing a dorsal twisted geniculate awn, 
the upper empty ones or those infolding staminate flowers awnless; palet 2-cleft or 2- 
toothed, narrow. Stamens3. Styles distinct. Grain deeply furrowed, usually pubescent. 
1. Avena sativa L. Annual. Stems 8-15 dm. tall: leaf-blades flat, 2.5 dm. long 
or less, 5-10 mm. wide or more : panicle usually 1.5—4 dm. long, its branches erect or ascend- 
ing: empty scales of the spikelet 2-3 em. long, acuminate, the flowering ones shorter, 
awned or awnless. 
In fields and waste places, escaped from cultivation nearly every where in civilized North America 
Summer. OAT. 
73. ARRHENATHERUM Beauv. 
Tall perennial grasses, with flat leaf-blades and terminal open or contracted panicles. 
Spikelets 2-flowered, the lower flowerstaminate, the upper one perfect or pistillate, the rachilla 
articulated above the empty scales and prolonged beyond the flowers. Scales 4, the 2 outer 
empty, persistent, thin-membranous, keeled, the flowering scales more rigid, somewhat 
toothed at the apex, the lower one bearing near the base a long dorsal twisted and genicu- 
late awn, the upper scale awnless, or short-awned below the apex ; palet 2-keeled, hyaline, 
narrow. Stamens 3. Styles short, distinct. Stigmas plumose. Grain hardly sulcate. 
1. Arrhenatherum elatius (L.) Beauv. Stems 6-12 dm. tall, erect: leaf-blades 
6-30 cm. long, 2-8 mm. wide, rough: panicle 1-3 dm. long, its branches erect: empty 
