66 Karl M. Wiegand and Arthur J. Eames 



e. Flowering glumes acute, thinner; anthers 1-1.2 mm. long; upper ligules 

 0.3-1.5 mm. long. 4. P. saltucnsis 



d. Intermediate nerves obscure ; midrib and lateral nerves hairy ; anthers 

 purple, 0.5-0.8 ( 1 ) mm. long ; branches of the panicle not nodding. 



5. P. paludigena 

 c. Branches of the panicle in (3's) 4's or 5's. 



d. Flowering glume pubescent between the nerves, mostly obtuse, strongly 

 5-nerved; anthers purple, 1.6-1.8 mm. long; panicle silvery green, open, its 

 branches more or less reflexed; ligule 1-1.5 (2.5) mm. long. 



6. P. sylvestris 

 d. Flowering glume glabrous between the nerves, acute ; branches of the 



panicle not reflexed. 

 c. Marginal nerves of the flowering glume glabrous, the keel hairy. 

 /. Intermediate nerves of the flowering glume obscure ; spikelets 4-6 mm. 

 long ; anthers 0.4-0.7 mm. long, pink ; ligule 1 mm. long or less ; sheaths 

 smooth ; inflorescence silvery green, without spikelets close to the 

 rhachis. 7. P. alsodes 



f. Intermediate nerves prominent ; spikelets 3.2-3.6 mm. long ; anthers 

 1.6 mm. long, pale; ligule 5-6 mm. long; sheaths rough; inflorescence 

 yellowish green or purplish, with normal rays and, in addition, many 

 spikelets on short branches closer to the rhachis. 8. P. trivialis 

 e. Marginal nerves, and also the keel, of the flowering glume hairy; spike- 

 lets green or purple. 

 /. Intermediate nerves prominent; glumes 1.4-1.8 mm. wide; ligule 0.5- 



1.5 mm. long; anthers 1.4-1.5 mm. long, purple. 9. P. pratcnsis 



f. Intermediate nerves obscure; glumes 1-1.4 mm. wide; anthers pale; 

 panicle looser and often larger. 

 g. Ligule 0.5 mm. long; spikelets (3.5) 4-4.5 mm. long; anthers 1.2-1.4 

 mm. long ; leaves spreading at right angles. 10. P. nemoralis 



g. Ligule 2-A mm. long ; spikelets 2.5-4.5 mm. long ; anthers 0.8-1 mm. 

 long; leaves erect or ascending. 11. P. palustris 



1. P. annua L. 



Lawns, cultivated grounds, and waste places, in moist, rich soils; common.* April- 

 Oct. 



Nearly throughout N. A. Naturalized from Eu. 



2. P. compressa L. Canada Blue Grass. Wire Grass. 



Dry banks, waste places, and the borders of woods, in rather sterile, mostly 

 gravelly soil, or in cinders ; common. June-Aug. 



Almost throughout N. A. Naturalized from Eurasia. 



Woodland forms have smaller spikelets and a more open inflorescence (var. 

 sylvestris Torr.). This is clearly an ecological variation. 



3. P. debilis Torr. 



Dry open woodlands and scrubby banks, in sandy or gravelly, nearly neutral, 

 soils, under oak, chestnut, or pine, rarely under maple or beech; frequent. May 15- 

 June. 



Thatcher Pinnacles; w. side of Cayuta Lake; hills s. of Mecklenburg; Cascadilla 

 woods; Pleasant Grove Brook; glen between Renwick and McKinneys ; n. of Esty 

 Glen; Ringwood (D. in C. U. Herb.); Salmon Creek, n. of Ludlowville; n. of 

 Genoa village ; Lowery Ponds. 



N. Y. and Ont. to Iowa. 



4. P. saltuensis Fernald & Wiegand. (See Rhodora 20: 122. 1918.) 



In situations similar to the preceding, but possibly in more limy gravels, mostly 

 under maple, beech, or pine; scarce. May 15-June. 



