GRASS FAMILY. 



201 



77- POA L. Sp. PL 67. 1753. 



Annual or perennial grasses with flat or convolute leave* and contracted or open pan- 

 icles. Spikelets 2-6-flowered, compressed, the rachilla usually glabrous; flower* perfcct/or 

 rarely dioecious. Scales membranous, keeled; the 2 lower empty, i-3-neryed; the flower* 

 ing scales longer than the empty ones, generally with a tuft of cobwebby bain at the baa*. 5. 

 nerved, the marginal nerves usually pubescent, often also the dorsal one; paletsa littk shorter 

 than the scales, 2-nerved or 2-keeled. Stamens 3. Styles short, distinct Stigma* plumos*. 

 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 region* The BMW 

 lish name Meadow-grass is often applied to most of the species. Beside* the following MM 

 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. i. p. 



Flowering scales 3-nerved, or obscurely 5-nerved, webby at the base. t. P. 

 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. alf-ina 

 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. P. lara. 



Flowering scales strongly pubescent all < 4. / at>f>rr*.-iaia 



Branches widely spreading, flexuous, smooth. 7 /' 



Branches of the panicle rough, erect or ascending. 



Lower flowering scale i"-Uf" long. ia. P. mfmora 



Lower flowering scale 2" long. n. P. gl>r 



Spikelets exceeding 3" in length. 23. P. glitmarit. 



Grasses not exclusively of far northern or high mountain regions; culms generally tall. 

 Culms strongly flattened. 3. P. comf>reu*. 



Culms terete or but slightly flattened. 



Panicle lax; branches long, slender, naked half their length, usually widely preading 

 Basal leaves much shorter than the culm. 



Pedicels commonly shorter than the spikelets. 



Flowering scales obscurely nerved; spikeleta I J<"-4" long. 13. P. Jtait. 

 Flowering scales prominently nerved. 

 Lateral nerves silky-pubescent. 



Spikelets a"-2^" long; flowering scales not pubescent between the 



nerves; ligule truncate. 8. P. f>rat< 



Spikelets 3-4" long; flowering scales minutt-ly pubencent below 

 between the nerves; ligule acute. 9. P. f>ttudo(>raU*tit. 



lateral nerves naked ; spikelets iV long. Jo. /'. tm-ialit. 

 Pedicels commonly equalling or much exceeding the spikelets. 

 Flowering scales rounded or retuse at the apex: 



Not webbed at the base, pubescent below. P. atHummalii. 



Webbed at the base, glabrous. 14 /' dftnln. 



Flowering scales obtuse or acute, webbed at the base. 



Flowering scales about i%" long, often pubescent between the nerve* 



toward the base. 16. P. syl: 



Flowering scales i X"-2" long, glabrous between the nerve*: 



Obscurely nerved, very acute, midnerve pubescent toward the bs*e. 



17. P. alsodft. 



Plainly nerved; nerves pilose. 



Basal leaves about equalling the culm; culm leaves short. 19. / 

 Panicle contracted; the branches short, erect or ascending, mostly *pikelet-beanna; 



nearly to the base; western species. 

 Flowering scales erose-truncate, very pubescent below between the- -i 



nerves. 

 Flowering scales acutish, nearly or quite glabrous. 



i. Poa annua I,. Annual Meadow Grass. 

 Lx>w Spear-grass. (Fig. 459.) 



Poa annua L. Sp. PI. 68. 1753- 



Culms 2 x -i tall, from an annual root, erect or 

 decumbent at the base, somewhat flattened, smooth. 

 Sheaths loose, usually overlapping; ligule about 

 i" long; leaves ^'-4' long, %"-iW wide, 

 smooth; panicle Y^'-Af in length, open, branches 

 spreading, ^'-i,^' long, naked at the base; spike- 

 lets 3-5 -flowered, T.Yz"--iW 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 \W-*W 

 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. 



