POACEAE 153 



Midnerve of the flowering scale pubescent the whole length, or 



nearly so. 



Flowering scales about 2.5 mm. long, obtuse. 7. P. nytvestrie. 



Flowering scales about 4 mm. long, acute. 8. P. Woljii. 



** Panicle contracted, its branches erect or nearly so : spikelets crowded. 

 Flowering scales strongly pubescent at the base with very long 



crimped hairs, the midnerve and lateral nerves pubescent. 9. P. arachnifera. 



Flowering scales with fewer crimped hairs at the base, the nerves 



all glabrous. 10. P. glabrescens. 



b. Flowering scales with no crimped hairs at the base. 



Panicle loose and open, its branches long and widely spreading and spike- 

 let-bearing only above the middle. 11. P. autumnalis. 

 Panicle contracted, its branches short and erect or nearly so, spikelet- 



bearing to the base or nearly so. 12. P. pratericola. 



B. Plants dull bluish green, with long stout often branching rootstocks : stems 



much compressed. 13. P. compressa. 



1. Poa annua L. Stems 5-30 cm. tall, erect, or decumbent at the base : leaf-sheaths 

 loose, usually overlapping ; blades 1-10 cm. long, 1.5-3 mm. wide : panicle 1-10 cm. long, 

 its branches spreading : spikelets 3-5-flowered, 3-5 mm. long, the flowering scales 2.5-3 

 mm. long. 



In waste and cultivated places nearly throughout North America. Naturalized from Europe. 

 Native also of Asia. Spring to fall. __ 



2. Poa Chapmaniana Scribn. Stems 7-15 cm. tall, erect, rigid': leaf-sheaths tight, 

 mostly at the base of the stem ; blades 1-2.5 cm. long, 2 mm. wide or less : panicle 2.5-5 

 cm. long : spikelets 3-7-flowered, 2. 5-3 mm. long, the flowering scales obtuse, webbed at the 

 base and sometimes with hairs on the more prominent nerves. PP. cristata Chapm., not ^ 

 Walt] 



In dry soil, Kentucky and Tennessee to Georgia, Florida and Alabama. Spring. 



3. Poa trivialis L. Steins 3-9 dm. tall, usually decumbent at the base : leaf-sheaths 

 very rough ; blades 5-18 cm. long, 2-4 mm. wide, rough : panicle 1-1.5 dm. long : spike- 

 lets 2-3-flowered, 3 mm. long, the scales acute, the flowering scales 2-3 mm. long, 5-nerved, 

 the intermediate nerves prominent. 



In meadows and waste places, New Brunswick to Michigan and Georgia. Naturalized from 

 Europe. Summer. 



4 Poa alsodes A. Gray. Stems 2-8 dm. tall : leaf -blades usually rough, 2-4 mm. 

 wide, those on the stem 5-20 cm. long, the basal ones longer : panicle 8-20 cm. long, its t^ 

 branches spikelet-bearing at the ends : spikelets 2-3-flowered, about 5 mm. long, the flow- 

 ering scales acute, about 4 mm. long, the intermediate nerves very faint. 



In woods and thickets, Nova Scotia to Ontario, Minnesota, North Carolina and Tennessee. Spring 

 and summer. 



5. Poa prate" nsis L. Stems 3-12 dm. tall : leaf -blades smooth or rough, 1-6 mm. 

 wide, those on the stem 5-15 cm. long, the basal much longer : panicle 6-20 cm. long, us-' 

 ually pyramidal : spikelets 3-5-flowered, 4-5 mm. long, the scales acute, the flowering 

 scales 3 mm. long, 5-nerved. 



In meadows, fields and woods, almost throughout North America. Widely cultivated for hay. 

 Also in Europe and Asia. Summer. KENTUCKY BLUE GRASS. JUNE GRASS. 



6. Poa brevifoiia Muhl. Stems 3-9 dm. tall, erect : leaf-blades smooth beneath, 

 rough above, 2-4 mm. wide, abruptly acute, those on the stem 1-10 cm. long, the upper- 

 most sometimes almost wanting : panicle 6-13 cm. long, its branches widely spreading or 

 often reflexed, spikelet-bearing at the ends : spikelets 3-6-flowered, 5-7 mm. long, the 

 flowering scales 4-5 mm. long, obtuse, the intermediate nerves prominent. 



In rocky woods, southeastern New York to Illinois, North Carolina and Tennessee. Spring and 

 summer. 



7. Poa sylvestris A. Gray. Stems 3-9 dm. tall, slender : leaf -blades smooth beneath, 

 rough above, 2-6 mm. wide, those on the stem 4-15 cm. long, the basal much longer : 

 panicle 7-18 cm. long, the branches spreading or ascending, sometimes reflexed when old, 

 spikelet-bearing at the ends : spikelets 2-4-flowered, 2-4 mm. long, the flowering scales 

 about 2.5 mm. long, obtuse. 



In thickets and meadows, New York to Wisconsin, Nebraska, Georgia and Louisiana. Summer. 



8. Poa Wdlfii Scribn. Stems tufted, 3-9 dm. tall : leaf -blades rather lax, flat, 2-3 

 mm. wide, those on the stem 5-10 cm. long, the basal ones longer : panicle 7-15 cm. long, 

 its branches long and lax, drooping, spikelet-bearing toward the end : spikelets 2-4-flow- 

 ered, 5-6 mm. long, the acute flowering scales about 4 mm. long, strongly pubescent on the 

 midnerve and the lateral nerves, the intermediate nerves very prominent. 



In moist soil, Illinois, Tennessee and Kansas. Summer. 



9. Poa arachnifera Torr. Steins tufted, 3-9 dm. tall : leaf-blades erect, usually 

 folded when dry, smooth beneath, rough above, 4-23 cm. long, 3-6 mm. wide, abruptly 

 acute : panicle dense and contracted, sometimes interrupted below, 7-16 cm. long, its 



