POACEAE 81 



versely rugose, and enclosing a similar palet and a perfect flower, its opening turned toward 

 the rachis. Stamens 3. Styles distinct. Stigmas plumose. 



1. Brachiaiia platyphylla (Munro) Nash. Stems at first erect, finally prostrate and 

 rooting at the lower nodes, 4-6 dm. long : leaf -sheaths pubescent, commonly overlapping ; 

 blades flat, 5-10 cm. long, 7-12 mm. wide, lanceolate : spikes 2-5, rather distant, 3-6 cm. 

 long, the rachis broadly winged : spikelets ovate, glabrous, about 4 mm. long. 



In wet woods, Louisiana and Texas. Summer and fall. . 



27. SYNTHERISMA Walt. 



Annual grasses, with flat leaf-blades and an inflorescence composed of spike-like racemes 

 which are disposed in whorls, or scattered and approximate, at the summit of the stems. 

 Spikelets narrow, acute, in 2's or 3's on one side of the flat and winged or triangular rachis, 

 one of the spikelets generally longer pedicelled than the rest. Scales 3 or 4, the 3 outer 

 membranous, the first small or wanting, the fourth scale chartaceous, glabrous and shining,, 

 at length indurated, enclosing a palet of similar texture and a perfect flower. Stamens 3-. 

 Styles distinct. Stigmas plumose. [Digitaria Scop., not Heist.] CRAB GRASS. 



Rachis of the racemes with the angles naked, not winged : first scale wanting or 



sometimes present as an inconspicuous rudiment. 

 Second and third scales pubescent with appressed glandular tipped hairs : stems 



simple or sparingly branched at the base ; nodes 5 or fewer. 



Racemes usually short, 2-10 cm. long : spikelets less than 2 mm. l9ng. 1. S. flliforme. 



Racemes usually exceeding 10 cm. in length, rarely shorter : spikelets 2.25 



mm. long or more. 



Pubescence on the sheaths spreading : racemes commonly more than 5. 2. S. vittosum. 

 Pubescence on the sheaths appressed or nearly so : racemes commonly 



less than 4. 3. S. leucocomum. 



Second and third scales glabrous. 



Hairs on the sheaths appressed or nearly so : nodes 5 or fewer. 



Second scale % as long as the spikelet or less, rounded or truncate at the 



apex. 4. S. gracittimum. 



Second scale more than % as long as the spikelet, sparingly pilose at the 



acute apex. 5. S. Bakeri. 



Hairs on the sheaths widely spreading : nodes numerous. 6. S. Simpsonii. 



Rachis of the racemes with the lateral angles broadly winged, thus making it 



appear flat : first scale usually present, or generally wanting in nos. 7 and 8. 

 Pedicels terete or sometimes obscurely angled, sparingly if at all hispidulous. 

 Sheaths and leaf-blades strongly papillose-hirsute: rachis of the racemes 



0.8 mm. wide or less ; second scale % as long as the spikelets or less. 7. S. serotinum. 



Sheaths and leaf-blades glabrous: rachis of the racemes 1 mm. wide or 



more ; second scale nearly as long as the spikelet. 8. S. humifusum* 



Pedicels sharply 3-angled, the angles strongly hispidulous. 



Sheaths strongly papillose-hirsute : racemes commonly more than 3. 



Racemes very slender, the rachis usually less than 0.5 mm. wide : spike- 

 lets i/ 5 as wide as long, acuminate : fourth scale greenish when ma- 

 ture. 9. S. setosum. 

 Racemes stouter, the rachis usually exceeding 0.7 mm. wide : spikelets % 

 as wide as long or more, acute : fourth scale yellowish white when 

 mature. 



Spikelets usually less than 3 mm. long, the second scale % as long as 

 the spikelet or less, the third scale with the first and second nerves 

 on each side hispid above the middle. 10. S. sanguinale. 



Spikelets commonly more than 3 mm. long, the second scale more 

 than % as long as the gpikelet, the third scale with the nerves 

 smooth. 11. S. flmbriatum. 



Sheaths glabrous or nearly so : spikelets about 4 mm. long : racemes 2. 12. 'S. barbatum. 



1. Syntherisma filifdrme (L. ) Nash. Stems 1.5-7 dm. tall : leaf -sheaths papillose-hir- 

 sute, or the uppermost one glabrous ; blades 3-20 cm. -long, 1-4 mm. wide, erect, usually 

 glabrous below, papillose-hirsute above toward the base : axis of the inflorescence 1-3 cm. 

 long : racemes 2-5, 2-10 cm. long, erect or ascending, alternate : spikelets about 1.8 mm. 

 long, 0.75 mm. wide, elliptic, acute, in pairs ; first scale wanting, the second and third 

 scales appressed-pubescent with long glandular-tipped 'hairs, the former 3-nerved and about 

 | as long as the 7 -nerved third scale, the fourth scale slightly exceeding the third, deep 

 chestnut brown when mature, striate. [Panicum filiforme L.] 



In dry sandy soil, Massachusetts to Michigan, North Carolina and the Indian Territory. Summer. 



2. Syntherisma villosum Walt. Stems densely tufted, 6-14 dm. tall : lower leaf- 

 sheaths papillose-hirsute, the uppermost one sometimes glabrous ; blades 7-25 cm. long, 

 3-6 mm. wide, erect or nearly so, smooth beneath, rough above, the lower surface more or 

 less papillose-hirsute, the upper leaves glabrous : axis of the inflorescence 3-9 cm. long ; 

 racemes 2-8, usually more than 5, generally 12-15 cm. long, erect or ascending, alternate : 

 spikelets 2.5 mm. long, about 0.8 mm. wide, elliptic, acute, usually in 3's, the first scale 

 wanting, the second and third scales appressed-pubescent with long glandular-tipped hairs, 



