52 American Midland Naturalist Monograph No. 2 



2. Spikelets 1.5-2 cm. long, subsessile; in shallow water or wet soil. May- 



Aug. [G. fluitans of auth., not R. Br.} G. septentrionalis Hitchc. 



1. Spikelets ovate, more or less compressed, not more than 6 mm. long; panicles 

 usually nodding. 



3. Lemmas broadly ovate, obscurely nerved; spikelets 3-4 mm. wide; wet 



ground in the n. part of the state. June-July 



G. canadensis (Michx.) Trin. 



3. Lemmas elliptical, the nerves prominent; spikelets 1-2.5 mm. wide. 



4. Spikelets 4-6 mm. long; wet ground, rare. Jo Daviess Co 



G. grandis S. Wats. 



4. Spikelets 2-3 mm. long; wet ground, common, June- July. [G. nervata 

 (Willd.) Trin.] G. striata (Lam.) Hitchc. 



5. PoA L. — Blue Grass. Meadow Grass 



1. Perennials; stems (20-) 30-140 cm. tall. 

 2. Plants with conspicuous horizontal rhizom'es. 



3. Stems terete, 30-120 cm. tall; leaves bright green; panicle open, 5-20 

 cm. long, the ascending or spreadina branches in whorls of 3-5; lem- 

 mas 3 mm. long, copiously webbed at base; roadsides, lawns, fields 



and woods, very common. May-June. Kentucky Blue Grass 



P. pratensis L. 



3. Stems compressed above, 20-40 cm. tall; leaves bluish green; panicle 



narrow, 3-8 cm. long; lemmas 2-2.5 mm. long, scarcely webbed; road- 

 sides, cultivated ground, waste places, common; nat. from Eurasia. 



June-July. Canada Blue Grass P. compressa L. 



2. Plants without horizontal rhizomes. 



4. Lemmas glabrous, except the webbed base; damp woods, rare, n. 111. 



June-Aug. [P. debilis Torr., not Thuill.} P. langiiida Hitchc. 



4. Lemmas puberulent or pubescent, at least on the keel. 

 5. Lemmas webbed, i.e., with a tuft of soft hairs at base. 



6. Marginal nerves of the lemmas glabrous; woods and thickets, rare. 

 May-June P. alsodcs Gray 



6. Marginal nerves of the lemmas pubescent. 

 7. Intermediate nerves of the lemmas obscure. 



8. Panicle 5-10 cm. long, the lower branches mostly in pairs; wet 

 ground, rare P. paludigena Fern. & Wieg. 



8. Panicle 10-30 cm. long, the lower branches mostly fascicled; 



damp meadows. July-Aug. [P. triflora Gilib.} 



P. palustris L. 



7. Intermediate nerves of the lemmas prominent. 



9. Branches of the panicle spikelet-bearing from the middle; 



spikelets 3-4 mm. long; woods and thickets. May-July 



P. sylvestris Gray 



9. Branches of the panicle spikelet-bearing only near the ends; 

 spikelets 5-6 mm. long; meadows, rare, w. III. Discovered 

 at Canton by J. Wolf in 1882 ....P. nolfii Scribn. 



