Tall perennial grasses, with flat leaf-blades and contracted or open panicles. Spikelets 2-flowered; lower flower staminate, upper perfect; rachilla extended beyond the flowers. Scales 4, the 2 lower empty, thin-membranous, keeled, very acute or awn-pointed, unequal, persistent, flowering scales rigid, 5-7-nerved, deciduous, the first bearing a long bent and twisted dorsal awn, inserted below the middle, the second unawned; palet hyaline, 2-keeled. Stamens 3. Styles short, distinct. Stigmas plumose. Grain ovoid, free. [Greek, referring to the awn of the staminate scale.]

Six species, natives of the Old World. Type species: Avena elatior L.

54 Arrhenatherum Beauv Agrost 55 P1 11 F 5 1812 531

1. Arrhenatherum Elatius (L.) Beauv. Oat-Grass

Fig. 531

Avena elatior L. Sp. PI. 79. 1753.

A. avenaceum Beauv. Agrost. 152. Name only. 1812.

A. elatius Beauv.; M. & K. Deutsch. Fl. 1: 546. 1823.

Glabrous, culms 2°-4° tall, erect, simple. Lower sheaths longer than the internodes; ligule 1" long; blades 2 1/2'-12' long, 1"-4" wide, scabrous; panicle 4'-12' in length, contracted, the branches erect, the lower l'-2' long; empty scales finely roughened, the second 4" long, the first shorter; flowering scales about.4" long.

In fields and waste places, Newfoundland to Ontario and Minnesota, south to Georgia and Tennessee and Nebraska. Also on the Pacific Coast. Naturalized from Europe. Tall, or False Oat-grass; Pearl-, Hever-, Evergreen-, Button- or Onion-grass; Button-, Butter- or Onion-twitch; Grass of the Andes. June-Aug.