GRAMINEAE. 



Vol. I. 



i. Cynosurus cristatus L. Dog's-tail-grass. 

 Fig. 603. 



Cynosurus cristatus L. Sp. PI. 72. 1753. 



Culms i°-2i° tall, erect, slender, simple, smooth, and 

 glabrous. Sheaths shorter than the internodes; ligule J" 

 long, truncate; blades ii'-s' long, i"-2" wide, smooth, 

 glabrous; spike-like panicle 2-4' in length, 2i"-6" wide, 

 long-exserted ; spikelets arranged in clustens, the terminal 

 fertile, the lower larger and sterile; scales of the former 

 about il" long, pointed or short-awned, the scales of the 

 sterile spikelets very narrow, pointed, strongly scabrous 

 on the keel. 



In fields and waste places, Newfoundland to Ontario, south- 

 ern New York and New Jersey. Adventive from Europe. 

 Hendon Bent, or Crested Dog's-tail-grass. Leghorn-straw- 

 grass. June-Aug. 



92. POA L. Sp. PL 67. 1753. 



Annual or perennial grasses with flat or convolute leaves 

 and contracted or open panicles. Spikelets 2-6-flowered, ■ 

 compressed, 'the rachilla usually glabrous ; flowers perfect, 

 or rarely dioecious. Scales membranous, keeled; the 2 lower empty, 1-3-nerved; the flower- 

 ing scales longer than the empty ones, generally with a tuft of cobwebby hairs at the base, 

 S-nerved, the marginal nerves usually pubescent, often also the dorsal one; palets a little 

 shorter than the scales, 2-nerved or 2-keeled. Stamens 3. Styles short, distinct. Stigmas 

 plumose. Grain free, or sometimes adherent to the palet. [Name Greek, for grass or 

 herbage.] 



A genus of about 150 species, widely distributed in all temperate and cold regions. The Eng- 

 lish name Meadow-grass is often applied to most of the species. Besides the following some 

 50 others occur in the western parts of North America. Type species : Poa pratensis L. 



Annuals. 



Flowering scales distinctly 5-nerved, not webby at the base. 

 Flowering scales 3-nerved, or obscurely s-nerved, webby at base. 

 Perennials. 



Innovations extravaginal, plants often bearing rootstocks or stolons. 

 Culms tufted, usually densely so. 



Rootstock slender ; plants often stoloniferous. 



Culms less than 8' tall ; low arctic or alpine grasses. 

 Flowering scales pubescent all over. 

 Flowering scales glabrous, or slightly pubescent. 

 Culms exceeding 8' tall- 

 Flowering scales not webby at the base. 



Flowering scales glabrous below between the nerves. 

 Flowering scales pubescent below between the nerves. 



Panicle narrow, contracted, its branches short, erect. 22. P. arida. 

 Panicle open, branches long, flexuous, spreading. 13. P. autumnalis. 

 Flowering scales webby at the base. 



Flowering scales glabrous ; culms manifestly compressed. 9. P. debilis. 

 Flowering scales somewhat pubescent ; culms round or little compressed. 

 Lateral nerves of the flowering scale glabrous. 



Plant yellowish green; flowering scales iJ4" long 8. P.trivialis. 

 Plant green; flowering scales i|4" long. 15. P.alsodes. 



Lateral nerves of the flowering scale pubescent. 



Lower half of the flowering scales densely villous between the nerves ; 



arctic grass. 18. P. cenisia. 



Lower half of the flowering scales glabrous between the nerves (some- 

 times somewhat pubescent in No. 14). 

 Spikelets 2" long or less ; panicle-branches dividing and spikelet- 

 bearing at or below the middle. 

 Intermediate nerves of the flowering scale obscure. 



Panicle erect, rarely exceeding 5', branches ascending. 



10. P. crocata. 

 Panicle drooping, up to 1°, or more, branches spreading. 



11. P. tri flora. 

 Intermediate nerves prominent. 



Midnerve of the flowering scales pubescent only below ; spike- 

 lets crowded on the branches. 12. P. pratensis. 

 Midnerve pubescent its whole length ; spikelets scattered on 

 the spreading often reflexed branches. 14. P. sylvestris. 

 Spikelets 2^" long or more; panicle-branches usually dividing and 

 spikelet-bearing only at the end. 

 Flowering scales very webby at the base, nerves strongly pilose ; 



innovation leaves much shorter than culms. 16. P.Wolfii.^ 

 Flowering scales little webby ; nerves sparsely pilose ; innovation 

 leaves equalling or exceeding culms. 17. P. brachyphylla. 



Rootstocks short and stout ; no stolons. 



1 . P. annua. 



2. P. Chapmaniana. 



3. P. abbreviata. 



4. P. laxa. 



6. P. glauca. 



