GRAMINEAE (GRASS FAMILY) 



155 



3. 



4. 



10. 

 IT. 



13. 



knnnsils. 

 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 ; 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 ; 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, \\ith lax leaves, the decumbent 

 bases of the culms forming louse 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 gabrous between the nerves below 7, 

 Panicle spreading ; lemma pubescent between the nerves 



below . . ■ 16 



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 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 5-0 mm. long . . . ' . 15. 



P. annua. 



P. Chapmaniana. 



P. compressa. 

 P. eminens. 



P. pratenfsis. 



P. brachyphylla. 



P. debilis. 

 P. alpina. 



6. P. laxa. 



P. glatica. 



P. autumnalia. 



11. 

 14. 



S. 

 9. 



12. 



P. trivia lis. 

 P. alsodes 



P. nemoralis. 

 P. triflora. 



P. sylvet^tris. 

 P. Woljii. 



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



1. P. In'nua 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 

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

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



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

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

 oblong ; florets icebbed at the base, the intermediate nenes of lemmas very 

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

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



* * Perennials. 



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



3. P. coMPRESSA L. (Caxada Blue Grass. "Wire 

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

 asceuding, iciry, 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. 

 4-0 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. ]\Iay-Sept. (Nat. 

 from Eu.^ Fig. 108. 



4. P. eminens 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 hen.vy. 8-10 cm. long, contracted ; spikelets .'>-5-fl(>w- 

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



1G3. p. compressa. 

 Panicle x ^/^. 

 S^'ikelet and floret x 2. 

 Lemma x 3. 



