GRAMINEAE (GRASS FAMILY) 



155 



ikiiniials. 

 Florets not webby at the base ; leramas distinctly 5-nerved . 

 Florets webby at the base ; intermediate pair of nerves obscure 

 Perennials. 

 Culms from extensively creeping rootstocks, not tufted. 

 Culms flattened ; spikelets 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 ; culma scarcely exceeding the basal leaves 

 No creeping rootstocks, but culms sometimes decumbent at base. 



Jiemma 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 decu 

 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 



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

 Intermediate nerves of lemma prominent ; florets obtuse 

 or acntisn. 

 Branches of panicle spikelet-bearing from the middle 

 8pikeletsS-4mm. long _...._ 

 Branches of panicle elongated, spikelet-bearing only at 

 the ends ; spikelets 5-6 mm. long 



1. P. annua. 



2. P. Chapmaniana. 



8, P. eomprenBn, 

 4. P. aminens. 



10. P. praiendis. 

 17. P. brachyphylla. 



18. P. debilis. 

 5. P. alpina. 



6. P. laaso: 



7. P. glauca. 



16. P. autumnaUs. 



11. P. 



14. P. alsodea 



8. P. nemoralia^ 

 ■ 9. P. trijlora. 



12. P.i 



15. P. WolJSd. 



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



i/ 1. p. Annua L. (Low Spear Grass.) Culms flattened, decumbent at base, 

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

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

 i mm. long; lemma distinctly h-nerved^ the nerves hairy below. — Cultivated and 

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



2. P. Chapmani£na Scribn. Similar to the preceding but more strict in 

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

 oblong; florets webbed 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 southw, Apr., May. 



* * Perennials. 



-»- Culms from extensively creeping rootstocks^ not tufted. 



3. P. coMPKissA 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, subsessiie, .3-6(rarely 9)-flowered, 

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

 at the summit, — Dry mostly sterile soil, Nfd. to S. C, and 

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

 from Eu.) Fio. 163. 



4. P. eminens J. S. Presl, Glaucous., glabrous, 8-9 dm. 

 high ; culms stout, erect, terete ; sheaths overlapping, clus- les. p. compressa. 

 tered on the sterile shoots; blades thick., 3-8 mm. wide; panicle x V4. 

 panicle heavy., 8-16 cm. long, contracted ; spikelets 3-5-flow- spikelet and floret x 2. 

 ered, 8-12 mm. long; lemmas 4-6 mm. long^ distinctly Lemma x 3. 



