L 



36 POACEAE 



on both sides; racemes 3-10, linear, 5-18 cm. long; spikelets elliptic-lanceolate, 

 acute; first glume minute, triangular; lemma apiculate, elliptic-lanceolate. P. 

 sanguinale L. Crab-grass. Cultivated ground and waste places: Mass. — 

 Fla. — Calif. — Wash.; Mex.; naturahzed from the Old World. Je-S. 



4. S. marginatum (Link) Nash. Stem 5-8 dm. long, prostrate at the base 

 and rooting at the nodes; sheaths densely papillose-hirsute; blades 5-8 cm. long, 

 3-10 mm. wide, flat, glabrous or pubescent; racemes 2-9, variously disposed, 

 2-12 cm. long; spikelets 3-4 mm. long, lance-oblong; first glume minute, triangu- 

 lar, glabrous; second and third glumes long-pubescent; lemma elliptic. Waste 

 places: Md. — Fla. — Max.— Utah; W, Ind., C.Am., and S. Am. 



9. VALLOTA Chase. 



Perennial grasses, with usually tufted stems, panicles usually densely hairy, 

 narrow or contracted. Spikelets numerous, articulated below the empty glumes, 

 1-flowered, lanceolate, acute or acuminate. Glumes 3, membranous, the second 

 and usually also the much shorter first densely silky-pilose or long ciliate on the 

 margins, often acuminate, and sometimes with a short bristle at the apex: the 

 lemma shorter, chartaceous, glabrous and shining, finally indurated, enclosing a 

 shorter palet. Styles distinct; stigmas plumose. 



1. V. saccharata (Buckl.) Chase. Erect perennial; stem 3-9 dm. high, 

 usually much-branched below; sheaths mostly exceeding the internodcs, glabrous 

 or papillose-hirsute; leaf-blades 5-15 cm. long, flat, 5 mm. wide or less, more or 

 less pubescent; panicle 1-2 dm. long; si)ikelets 3-3.5 mm. long, acute; first glume 

 minute, second and third glumes densely silvery-villous. Panicum saccharatum 

 Buckl. P. lachnaniMirn Torr. Trichacne saccaratum Nash. Dry hillsides: Tex. 

 — Colo. — Ariz. ; Mex. Son. — Suhmont. M v — S. 



10. pAnICXTM L. Panic-guass, Wttch-guass. 



Annuals or perennials. Spikelets in open or contraced panicles, 1-2-floworcd, 

 lanceolate, oblong, ovate to obovate or globose, obtuse to acute or acuminate. 

 Glumes 3, membranous, the first and second empty, the first tisually much 

 shorter than the spikelet, som.etimes minute, the third one empty or enclosing a 

 shorter hyahne palet and often also a staminate flower; lemma shorter and usually 

 more obtuse than the glumes, chartaceous, glabrous and shining, at lengtli in- 

 durated, enclosmg a palet. Styles distinct; stigmas plumose. 



Inflorescence truly paniculate. 



Basal leaf-blades long and narrow; spikelets lanceolate or ovate, acute or acuminate 

 Annuals. 



Branches of the panicle widely spreading, the weU developed pulvinus in their 

 axils long-hairy; spikelets lanceolate, acuminate. 1. P. barhipuhinatum. 

 Branches of the panicle ascending, rarely spreading, the pulvinus glabrous or 

 sparmgly hairy; spikelets ovate to ellipsoid, acute. 2. P. capillare. 

 Perennials with long scaly rootstocks and stolons. 3. P. zirqatum " 



Basal leaf-blades ovate to lanceolate, obtuse. 

 Spikelets less than 2 mm. long. 



Stem and sheaths sparingly pubescent, with spreading papillate hairs. 

 V ernal leaves glabrous or nearly so on the upper side. 



Autumnal stems branching from the lower nodes, forming a spreading 



bunch 1-1.5 dm. high. 4. P. occidentale. 



Autumnal stems branching from the middle nodes, forming widely 

 spreading mats. 5 p tennessecnse 



Vernal leaves pubescent on the upper side, especially 'towards the base. 

 bpiKelets 1.8-2 mm. long; autumnal form decumbent- spreading. 



Q., , . ^ tf ^ ^ , 6. P. pacificum, 



apikeiets 1.&-1.8 mm. long; autumnal form not decumbent-spreading. 



Stem and sheaths densely soft -pubescent; hairs scarcely papiUate. 



bpikelets more than 2 mm. long. 



Blades of stem-leaves elongated, narrowlv linear 



Spikelets glabrous or with a few scattered hairs: stem branching only 



Spikelets densely pubescent; stem branching above. 



TJto.1^^ ^r *- I . . 1^- ^- Wilcoiianujn. 



olades of stem-leaves lanceolate. 11. P. Scribneriamun 



Inflorescence with racemiform branche=i. 12. P. ^^n'sl^m 



