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GRASS FAMILY. 201 
as POA L.. DP e678 i753: 
Annual or perennial grasses with flat or convolute leaves and contracted or open pan- 
icles. Spikelets 2-6-flowered, compressed, the rachilla usually glabrous; flowers perfect, or 
rarely dioecious. Scales membranous, keeled; the 2 lower empty, I-3-nerved; the flower- 
ing scales longer than the empty ones, generally with a tuft of cobwebby hairs at the base, 5- 
nerved, the marginal nerves usually pubescent, often also the dorsal one; palets a little shorter 
than the scales, 2-nerved or 2-keeled. Stamens3. Stylesshort, distinct. Stigmas plumose. 
Grain free, or sometimes adherent to the palet. [Name Greek, for grass or herbage. ] 
A genus of about 100 species, widely distributed in all temperate and cold regions. The Eng- 
lish name J/eadow-grass is often applied to most of the species. Besides the following some 
50 others occur in the western parts of North America, 
Low annual or biennial grasses, the culms 12’ tall or less. 
Flowering scales distinctly 5-nerved, not webby at the base. 1. P. annua. 
Flowering scales 3-nerved, or obscurely 5-nerved, webby at the base. 2. P. Chapmaniana, 
Perennials, mostly with tall culms (Nos. 4-7 low). 
Grasses of far northern or high mountain regions, generally low. 
Leaves short; panicle-branches short, generally widely spreading. 6. P. alpina. 
Leaves longer, gradually narrowed to the apex. 
Spikelets less than 3’’ long. 
Branches of the panicle erect, smooth, slender, lax. 
Flowering scales glabrous or slightly pubescent. 5. £. laxva. 
Flowering scales strongly pubescent all over. 4. P. abbreviata. 
Branches widely spreading, flexuous, smooth, 7. P. centsta. 
Branches of the panicle rough, erect or ascending. 
Lower flowering scale 1'’-14"' long. 12. P. nemoralis. 
Lower flowering scale 2’’ long. 11. P. glauca. 
Spikelets exceeding 3/’ in length. 22. P. glumaris. 
Grasses not exclusively of far northern or high mountain regions; culms generally tall. 
Culms strongly flattened. 3. P. compressa. 
Culms terete or but slightly flattened. 
Panicle lax; branches long, slender, naked half their length, usually widely spreading. 
Basal leaves much shorter than the culm. 
Pedicels commonly shorter than the spikelets. 
Flowering scales obscurely nerved; spikelets 114'’-2'’ long. 13. P. flava. 
Flowering scales prominently nerved. 
Lateral nerves silky-pubescent. 
Spikelets 2'’-2's"’ long; flowering scales not pubescent between the 
nerves; ligule truncate. 8. P. pratensis. 
Spikelets 3/’-4’’ long; flowering scales minutely pubescent below 
between the nerves; ligule acute. 9. P. pseudopratensts, 
Lateral nerves naked; spikelets 134'’ long. 10. P. trivialis. 
Pedicels commonly equalling or much exceeding the spikelets. 
Flowering scales rounded or retuse at the apex: 
Not webbed at the base, pubescent below. 15. P. autumnalis. 
Webbed at the base, glabrous. 14. P. debilis. 
Flowering scales obtuse or acute, webbed at the base. 
Flowering scales about 14%’’ long, often pubescent between the nerves 
toward the base. 16. P. sylvestris. 
Flowering scales 1%4'/-2'' long, glabrous between the nerves: 
Obscurely nerved, very acute, midnerve pubescent toward the base. 
17. P. alsodes. 
Plainly nerved; nerves pilose. 18. P. Wolfit. 
Basal leaves about equalling the culm; culm leaves short. 19. P. brevifolia. 
Panicle contracted; the branches short, erect or ascending, mostly spikelet-bearing 
nearly to the base; western species. 
Flowering scales erose-truncate, very pubescent below between the silky-pubescent 
nerves. 20. P. arida. 
Flowering scales acutish, nearly or quite glabrous. 21. P. Buckleyana. 
1. Poa annua I, Annual Meadow Grass. 
Low Spear-grass. (Fig. 459. ) 
Poa annua I,. Sp. Pl. 68. 1753. 
Culms 2/—1° tall, from an annual root, erect or 
decumbent at the base, somewhat flattened, smooth. 
Sheaths loose, usually overlapping; ligule about 
1’ long; leaves %/-4’ long, 34’’-1%’’ wide, 
smooth; panicle '4/-4’ in length, open, branches 
spreading, \4’-114’ long, naked at the base; spike- 
lets 3-5-flowered, 114’’-2%’’ long; lower scales 
smooth, the first narrow, acute, I-nerved, about 
two thirds as long as the broad and obtuse 3- 
nerved second one; flowering scales 114//-114// 
long, distinctly 5-nerved, the nerves pilose below. 
In waste and cultivated places nearly throughout 
North America. Naturalized from Europe. Native 
also of Asia. May-Oct. 
