Mostly perennial tufted grasses, with flat leaf-blades and spike-like or open panicles. Spikelets 2-4-flowered, the flowers all perfect, or the uppermost staminate; rachilla glabrous or pilose, extended beyond the flowers. Scales 4-6, membranous, the 2 lower empty, unequal, acute, persistent; flowering scales usually shorter than the empty ones, deciduous, 2-toothed, bearing a dorsal awn below the apex, or the lower one sometimes awnless. Palet narrow, hyaline, 2-toothed. Stamens 3. Styles distinct. Stigmas plumose. Grain free, enclosed in the scale. [Latin, referring to the three bristles (one awn and two sharp teeth) of the flowering scales in some species.]

About 60 species, widely distributed in temperate or mountainous regions. Besides the following, about 8 others occur in the western parts of North America. Type species: Avena striata Lam.

Flowering scales all bearing long dorsal awns.

Panicle contracted, dense; flowering scales 2 1/2" long or less.

1.

T. spicatum.

Panicle open, loose; flowering scales 2 l/2" long or more.

2.

T. flavesccns.

Lower flowering scale not bearing a long dorsal awn, a rudiment sometimes present.

3.

T. pennsylvamcum.

1. Trisetum Spicatum (L.) Richter. Narrow False Oat

Fig. 523

Aira spicata L. Sp. PI. 64. I753. Aira subspicata L. Syst. Veg. Ed. 10, 673. 1759-Avena mollis Michx. Fl. Bor. Am. 1: 72. 1803. Trisetum subspicatum Beauv. Agrost. 180. 1812. T. spicatum Richter, PI. Europ. 1: 59. 1890.

Softly pubescent or glabrous, culms 6'-2° tall, erect, simple. Sheaths usually shorter than the internodes; ligule1/2"-1" long; blades 1'-4' long, '-2" wide; panicle spike-like, 1'-5' in length, often interrupted below, its branches 1 1/2' or less long, erect; spikelets 2-3-flowered, the empty scales hispid on the keel, shining, the second about 2 1/2" long, the first shorter; flowering scales 2"-2 1/2" long, acuminate, scabrous, each bearing a long bent and somewhat twisted awn.

In rocky places, Labrador to Alaska, south on the mountains to North Carolina, New Mexico and California. Also in Europe and Asia. Downy Oat-grass. Aug.-Sept.

1 Trisetum Spicatum L Richter Narrow False Oat 523

2. Trisetum Flavescens (L.) Beauv. Yellow False Oat

Fig. 524

Avena flavescens L. Sp. PI. 809. 1753. Trisetum pratense Pers. Syn. 1: 97. 1805. T. flavescens Beauv. Agrost. 88. 1812.

Culms 1 1/2°-2 1/2° tall, erect, simple, smooth and glabrous. Sheaths shorter than the internodes, more or less pubescent; ligule 1/2" long; blades 1 1/2-5' long, 1"-3" wide, scabrous, sometimes sparingly hairy; panicle open, 2'-5' in length, the branches ascending or erect, somewhat flexuous, naked below, the lower 1'-2' long; spikelets 3-4-flowered; empty scales smooth and glabrous, the second acute, 2 1/2" long, the first about half as long, narrower, acuminate; flowering scales 2 1/2"-3" long, scabrous, bearing a long bent and twisted awn.

Introduced into Missouri and Kansas. Native of Europe and Asia. Panicle yellow, turning dull brown. Golden, Tall or Yellow Oat-grass. July-Aug.

2 Trisetum Flavescens L Beauv Yellow False Oat 524

3. Trisetum Pennsylvanicum (L.) Beauv. Marsh False Oat Or Oat-Grass

Fig. 525

Avena pennsylvanica L. Sp. PI. 79. 1753.

Avena palustris Michx. Fl. Bor. Am. 1: 72. 1803.

Trisetum peunsylvanicum Beauv.; R. & S. Syst. 2: 658. 1817.

Trisetum palustre Torr. Fl. U. S. 1: 126. 1824.

Culms 1°-3° tall, erect, simple, slender and often weak, smooth and glabrous. Sheaths shorter than the internodes, sometimes scabrous; ligule 1/2" long; blades 1'-6' long, 1"-3" wide, rough; panicle 2'-8' in length, yellowish, narrow, the branches ascending, the lower 1'-2' long; spikelets 2-flowered; outer scales smooth, shining, subequal, the second 2"-2 1/2" long; flowering scales 2"-2i" long, scabrous, the lower not long-awned, but a rudimentary awn sometimes present, the upper with a long bent and twisted awn.

In swamps and wet meadows, Massachusetts to Illinois, south to Florida and Louisiana. Ascends to 3500 ft. in Virginia. Panicle sometimes loose and nodding. June-July.

3 Trisetum Pennsylvanicum L Beauv Marsh False Oat  525