POACEAE. 13 



the awn 7-15 mm. long, geniculate, twisted at the base; pedicellate spikelet as 

 large as the sessile, staminate, awnless. — Common, generally in rather moist 

 soil. — Sum. and fall. 



4. SORGHASTHUM Nash. Usually tall perennial grasses, with flat leaf- 

 blades and terminal panicles with the primary branches usually solitary and 

 branched from the base, hence appearing as if whorled. Sessile spikelets dor- 

 sally compressed, of 4 scales, the outer 2 indurated, often hairy, the third and 

 fourth scales hyaline, the latter long-awned, the awn spiral at the base. Pedi- 

 cellate spikelets wanting, or very rarely present as a minute rudiment, usually 

 only the hairy pedicels present, a single one at the side of each sessile spikelet, 

 or 2, one on each side, at the end of the branches. Stamens 3. 



1. S. nutans (L.) Nash. Stems 1-2.5 m. tall: leaf -blades 6 dm. long or less, 13 

 mm. wide or less, very rough: panicle 2-5 dm. long, loose, the apex usually nod- 

 ding: spikelet 6-8 mm. long, lanceolate, the awn 1-1.5 cm. long. — N. S. Com- 

 mon, in old fields and on roadsides. — Sandstones and shales, schists. — Indian- 

 grass. Wood-grass. 



5. PASPAIjUM L. Usually perennial grasses with flat leaf -blades and an. 

 inflorescence composed of one or more unilateral racemes, arranged singly, in 

 pairs, or in panicles. Spikelets 1 -flowered, obtuse, or rarely short-acuminate, 

 nearly sessile or short-pedicelled, alternately disposed, singly or in pairs, in 2 

 rows on one side of a narrow and usually wiiiged rachis. Scales 3, rarely 4, the 

 2 outer, rarely 3, empty, membranous, usually equal in length, the flowering 

 scales glabrous and shining, more or less convex, with its back turned toward the 

 rachis, at length indurated, enfolding a shorter palet of similar texture and a 

 perfect flower. Stamens 3. 



Plants without raceme-bearing branches from the uppermost sheath. 

 Spikelets oval, % as thick as broad or more, the outer scales firm. 



1. P. laeve. 

 Spikelets circular or nearly so, about ^^ as thick as 



broad, the outer scales very thin. 2. P. circulare. 



Plants with raceme-bearing branches from the uppermost 



sheath. 3. P. Muhleniergii. 



1. P. laeve Michx. Stems tufted, 3-6 dm. tall: leaf -sheaths compressed, 

 glabrous; blades short, those on the stem usually less than 1.5 dm. long, 5-8 mm. 

 wide, pubescent above near the base: racemes 2 or 3, spreading, 4-8 cm. long: 

 spikelets glabrous, oval, 2.5-3 mm. long, 2-2.5 mm. wide. — Common, in pas- 

 tures and fields and on roadsides. 



2. P. circulare Nash. Stems tufted, 4-8 dm. tall: leaf -sheaths hirsute with 

 long hairs, compressed ; blades 2 dm. long or less, 5-8 mm. wide, glabrous beneath 

 or hirsute along the midnerve, the upper surface hirsute with long hairs: 

 racemes 2-4, spreading or ascending, 4-6 cm. long: spikelets glabrous, about 

 2.5 mm. in diameter. — S. Eare, in moist soil. — Schists. 



3. P. Muhlenbergli Nash. Stems tufted, at first erect, finally reclining, 4-8 

 dm. tall, smooth and glabrous: leaf -blades 0.5-2 dm. long, rarely longer, usually 

 7-11 mm. wide, or sometimes narrower, ciliate on the margins with usually long 

 hairs, more or less pubescent on both surfaces with long hairs: racemes 5-10 cm. 

 long: spikelets glabrous, about 2 mm. long and 1.8 mm. wide, oval or broadly 

 obovate. — - Eather common, in fields and thickets. 



6. SYNTHERISMA Walt. Annual grasses, with flat leaf-blades and an 

 inflorescence composed of spike-like racemes which are disposed in whorls, or 

 scattered and approximate, at the summit of the stems. Spikelets narrow, acute, 



