GRAMINEAE (GRASS FAMILY) 



155 



Annuals. 

 Florets not webby at the base ; lemmas distinctly 5-nerved 

 Florets webby at the base ; intermediate pair of nerves obscure 

 Perennials. 

 Culms from extensively creeping rootstocks, not tufted. 



Culms flattened ; spikeiets not over 6 mm. long 



Culms terete; spikelets 8 mm. or more long 



Culms tufted. 



Creeping rootstocks present. 

 Panicle crowded ; culms much exceeding the leaves .... 

 Panicle diffuse ; culms scarcely exceeding the basal leaves 

 No creeping rootstocks, but culms sometimes decumbent at base. 



Lemma glabrous 



Lemma pubescent at least on the keel. 

 Culms upright from a stout crown or caudex ; leaves short and flat 

 Culms from a more slender base forming loose tufts, often decum- 

 bent. 

 Culms rarely over 3 dm. high, with lax leaves, the decumbent 

 bases of the culms forming loose tufts ; lemma pubescent 

 but very sparsely webbed ; alpine or northern plants . 

 Culms taller, or if low, stiff and with scarcely decumbent bases. 

 Lemma not webbed at base. 



Panicle narrow ; lemma glabrous between the nerves below 

 Panicle spreading : lemma pubescent between the nerves 

 below ..... 

 Lemma webbed at base. 

 Marginal nerves glabrous. 



Lemma prominently nerved ; sheaths scabrous . 

 Lemma obscurely nerved ; sheaths smooth 

 Marginal nerves pubescent. 



Intermediate nerves of lemma obscure ; florets acute. 

 Panicle erect, 0.4-1 dm. long (rarely longer), branches 

 ascending 



1. P. annua. 



2. P. Chapmaniana. 



".. P. cornpreisaa. 

 4. /'. f.niineiis. 



10. P. prutennis. 

 IT. /'. hrachyphylla. 



13. P. dehilis. 

 5. P. alpina. 



6. P. laxa. 



7. P. glauca. 



16. P. antumnalis. 



11. P. trimalis. 

 14. P. (tlHodes. 



Panicle drooping, 1-3 dm. long, branches spreading 

 Intermediate nerves of lemma prominent ; florets obtuse 

 or acutish. 

 Branches of panicle spikelet-bearing from the middle ; 



spikelets 3-4 mm. long 



Branches of panicle elongated, spikelet-bearing only at 

 the ends ; spikelets 5-6 mm. long .... 



8. P. nemoralia. 



9. /'. triflora. 



12. P. sylvestris. 

 15. P. Woljii. 



* Annuals., rarely over 2.5 dm. high., tufted. 



1. P. Annua L. (Low Spear Grass.) Culms flattened, decumbent at base, 

 sometimes rooting at tlie lower nodes ; sheaths loose; leaves very soft; panicle 

 pyramidal, 3-8 cm. long, rarely longer; spikelets crowded, 3-6-flowered, about 

 4 mm. long ; lemma distinctly d-nerved, the nerves hairy helow. — Cultivated and 

 waste grounds, everywhere. Apr.-Oct. (Nat. from Eu.) 



2. P. Chapmaniana Scribn. Similar to the preceding but more strict in 

 habit; culms terete, erect; sheaths close, mostly at the base; panicle more 

 oblong; florets ivehbed at the base, the intermediate nerves of lemmas very 

 obscure, the middle and marginal nerves sometimes hairy below. — Dry soil, 

 Va. to s. 111., and south w. Apr., May. 



* * Perennials. 



H- Culms from extensively creeping rootstocks, not inftod. 



3. P. coMPRESSA L. (Canada Blue Grass. Wire 

 Grass.) Bluish-green, 2-6 dm. high; culms geniculate- 

 ascending, wiry, 'flattened; panicles 2-8 cm. long, narrow, 

 the usually short branches in pairs, spikelet-bearing to the 

 base ; spikelets crowded, subsessile, 3-6 (rarely 9) -flowered, 

 4-6 mm. long ; lemmas obscurely nerved, more or less bronzed 

 at the summit. — T>Yy mostly sterile soil, Nfd. to S.C, and 

 westw. ; also cultivated as a pasture grass. May-Sept. (Nat. 

 fromEu.) Fig. 163. 



4. P. §minens J. S. PresL Glaucous, glabrous, 3-9 dm. 

 high ; culms stout, erect, terete ; sheaths overlapping, clus- 

 tered on the sterile shoots ; blades thick, 3-8 mm. wide ; 

 panicle heavy, 8-16 cm. long, contracted ; spikelets 3-5-flow- 

 ered, 8-12 mm. long; lemmas 4-5 mm. long, distinctly 



compressa. 



Si)ikelet and floret x 2. 

 Lemma x 3. 



