GRAMINEAE. 137 



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 English 

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

 some 75 others occur in the western parts of N. Am. : 



Annuals or biennials; culms low and densely tufted, commonly less than 2 dm. long. 

 Flowering scale distinctly 5-nerved, not webby at the base. i. P. annua. 

 Flowering scale 3-nerved, or obscurely 5-nerved, webby at the base. 



2. P. Chapmaniana. 



Perennials; culms tall, usually exceeding 2 dm. long (shorter in Nos. 3 and 4). 

 A. Culms tufted, usually densely so. 

 a. Panicle open, loose. 



i. Rootstocks slender; often stoloniferous. 



Culms less than 2 dm. tall; low arctic or alpine grasses. 



Flowering scales pubescent all over. 3. P. abbreviata* 



Flowering scales glabrous or slightly pubescent. 



4. P. laxa. 

 Culms exceeding 2 dm. in height. 



Basal leaves much shorter than the culms. 

 Flowering scales not webby at the base. 



Panicle with short stiff branches; flowering scales glabrous 



below between the nerves. 8. P.glauca. 



Panicle with long slender flexuous branches; flowering 

 scales pubescent below between the nerves. 



12. P. antumnalis. 

 Flowering scales webby at the base. 



Flowering scales glabrous; culms manifestly compressed. 



10. P. debilis. 

 Flowering scales pubescent on one or more of the nerves; 



culms round or but little compressed. 

 Lateral nerves of the flowering scale glabrous. 



Plant yellowish green ; flowering scales 2.5 mm. 



long. 9. P. trivialis. 



Plant green; flowering scales 3.5 mm. long. 



13. P. alsodes. 

 Lateral nerves of the flowering scales pubescent. 



Lower half of the flowering scale densely villous 

 between the nerves; arctic grass. 



16. P. cenisia. 



Lower half of the flowering scale glabrous be- 

 tween the nerves; sometimes somewhat pu- 

 bescent in No. ii. 



Panicle-branches dividing and spikelet-bearing 

 usually at and above the middle; spike- 

 lets 4 mm. long or less. 

 Intermediate nerves of the flowering scale 



obscure. 



Culms usually rigid and 4 dm. or less 

 tall, the panicle generally less 

 than 1.5 dm. long. 



5. P. nemoralis. 



Culms usually 6-iodm. tall, the pani- 

 cle commonly 2-4 dm. long. 



6. P.flava. 

 Intermediate nerves prominent. 



Spikelets crowded on the spreading 

 or ascending branches ; midnerve 

 of the flowering scale pubescent 

 only below. 7. P. praten sis. 



Spikelets scattered on the spreading 

 often reflexed branches ; midnerve 

 pubescent its whole length. 



11. P. sylvestris. 

 Panicle-branches very long, dividing and 



spikelet-bearing only at the end; spikelets 5 

 mm. long. 14. P. Wolfii. 



