106 Bulletin VII. 1. 



(d) Taller (12 to 24 inches) panicle-branches spreading, 

 spikelet less crowded, flowering glumes with a 

 conspicuous web at the base and silky villous 

 along the dorsal and marginal nerves below 

 var. b. /axa. 



4. Culms not strongly flattened, panicle open, flowering glume 



compressed, keeled and plainly 5-nerved (at least when 

 dry) 5 



5. Pedicels for the most part (in each panicle) shorter than 



the spikelets 6 



5. Pedicels for the most part (in each panicle) equalling or 



much exceeding the spikelets 7 



6. Sheaths and leaves smoot'h, ligule % to i line long, broadly 



truncate 4. P. pratensis. 



(a) Radical leaves flat, nearly as broad as those of the 



culm var. a. pratensis. 



{b) Radical leaves very narrow, involute or filiform, 



often glaucescent .... var. b. afigustifolia. 



6. Sheaths and leaves rough, ligule 2 to 3 lines long, acute . . 



. .5. P. TRIVIALIS. 



7, Flowering glume with a broad, rounded-obtuse or retuse 



white scarious apex, not webbed at the base .... 



6. P. AUTUMNALIS. 



7. Flowering glume not rounded at the apex, webbed at the 



base 8 



8. Florets nearly or barely exceeding a line in length, rather 



blunt-pointed, minutely pubescent on the keel for its 

 whole length, and on the margins and over the whole 

 back below 7- P- sylvestris. 



8. Florets i)^ to 2 lines long, acute 9 



9. Flowering glumes narrow, lanceolate, acuminate, faintly 



nerved, minutely pubescent on the keel for one-half its 

 length, marginal nerves smooth .... 8. P. alsodes. 

 9. Flowering glumes broadly lanceolate, with rather broad, 

 scarious margins, acute, distinctly nerved (at least when 

 dry) silky-villous along the keel for ^ its length and on 

 the marginal nerves below; empty glumes broadly lanceo- 

 late, subequal, 3-nerved 9. P. Wolfii. 



10. Upper culm-leaf short (^ to i inch) abruptly sharp-pointed, 

 panicle branches capillary, widely spreading and few- 

 flowered above 10. P. brevifolia. 



10. Upper culm-leaf 2 to 6 inches long, panicle-branches rather 

 short, erect, or slightly spreading, densely many-flow- 

 ered II. P. ARACHNIFERA. 



I. Poa annua L. Low Spear-grass. Six- weeks grass. 



Plate XXXVI. Figure 141. 



A low, spreading annual, the erect or ascending, somewhat flat- 

 tened stems two to twelve inches high. Sheaths smooth, lax; leaf- 



