88 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



1. Poa annua L. 



A common weed in lawns and waste places. Flowering in early spring or even in 

 warm weather during the winter. Common throughout the warmer parts of the 

 U. S., and in the Old World. 



2. Poa chapmaniana Scribn. 



Arlington Farm ( Wheeler). Open ground, southern states. 



3. Poa compressa L. Canada bluegrass. 

 Grassland and waste places, especially in sterile soil; a weed in gardens. June. 



Introduced from Eur. and now distributed throughout theU. S. (Including P. com- 

 pretsa gracilis of Ward's Flora.) 



4. Poa cuspidata Nutt. 



Rocky woods; infrequent; mostly above the fall line. Apr. N. Y. to Ga. and 111. 

 (P. brachyphylla Schult.; P. brerifolia Muhl.) 



Except the introduced P. annua this is the earliest of all our grasses to bloom. 



5. Poa pratensis L. Kentucky bluegrass. 

 Common in grassland. May. Cultivated as a lawn and pasture grass in the cooler 



parts of the U. S. and well established; native of Eur. 



6. Poa autumnalis Muhl. 



Low woods; frequent. May. Southern states, north to Fa. (P.flexuosa Muhl.) 



7. Poa trivialis L. Rough-stalked meadow grass. 

 Moist places, ditches, and river banks; infrequent; along the Potomac above 



Georgetown. June. Introduced from Eur. 



8. Poa palustris L. 



Moist meadows; rare. July. Southern states, north to Pa.; also in Eur. and Asia. 

 (P. triflora Gilib.) 



9. Poa sylvestris A. Gray. 



Rocky woods; frequent. May. Eastern U. S. 



47. PANICULARIA Eabr. 



Spikelets terete, J .5-2 cm. long 1. p. septentrionalis. 



Spikelets ovate or oblong, usually not over 7 mm. long. 



Panicle contracted, oblong 2. P. obtusa. 



Panicle open, lax. 

 Spikelets 3-4 mm. wide; lemmas obscurely nerved. 



Lemmas about 2.5 mm. long; spikelets usually not over 5-riowered; middle 

 nodes of panicle with 3-5 primary branches; panicle 3-5 times branched. 



3. P. laxa. 



Lemmas a little over 3 mm. long; spikelets usually more than 5-fiowered; 



middle nodes of panicle with 1-3 primary branches; panicle 2-3 times 



branched 4. P. canadensis. 



Spikelets not over 2.5 mm. wide; lemmas prominently nerved. 

 Glumes short and rounded, the lower about 1 mm. long; lemmas about 2 mm. 



!ong g. P. nervata. 



Glumes oblong, the lower 1.5-2 mm. long; lemmas about 3 mm. long. 



6. P. pallida. 



1. Panicularia septentrionalis (Hitchc.) Bicknell. 



Marshes and river banks; infrequent; Bladensburg; Broadwater. June. North- 

 ernstates, south to Va. (Glyceria septentrionalis Hitchc. ; G. fluitans of Ward's Flora.) 



2. Panicularia obtusa (Muhl.) Kuntze. 



Swales and river banks; rare; Oxon Run (Steele). Aug. Near the coast, N. Eng. 

 and southward. (Glyceria obtusa Trin.) 



3. Panicularia laxa Scribn. 



Swales; rare; Terra Cotta Swamp (Ward); Suitland. June. Me. to Md. (Glyceria 

 laxa Scribn.; G. aquatica of Ward's Flora.) 



