60 POACEAE 



9. Schizachyrium triaristatum Nash. Stems 6-8 dm. tall, stoloniferous : leaf- 

 sheaths keeled, more or less hirsute on the margins near the summit ; blades 1.5 dm. long 

 or less, 3-5 mm. wide, hirsute above near the base : racemes single, 3-5 cm. long : sessile 

 spikelet 9-10 mm. long, acuminate, more than twice as long as the rachis-internode, the 

 first scale smooth or nearly so, the awn of the fourth scale 12-15 mm. long, geniculate, 

 more or less contorted, spiral at the base, the column not exserted ; pedicellate spikelet of 

 2 scales, 6-8 mm. long, the first scale hispidulous, 3-awned. 



In sand, Florida. Fall. 



10. Schizachyrium gracile (Spreng. ) Nash. Smooth and glabrous. Stems densely 

 tufted, slender, rigid, 3-6 dm. tall ; leaf-blades 2 dm. long or less, very slender, involute, 

 0.5 mm. in diameter or less": racemes long-exserted, single, 3-5 cm. long, silvery white : 

 sessile spikelet 5-6 mm. long, about again as long as the internode, the awn geniculate, 

 13-20 mm. long, tightly spiral to the bend, loosely so above, the column much exserted : 

 pedicellate spikelet consisting of a single scale, 1-2.5 mm. long, short-awned, the pedicel 

 about as long as or a little shorter than the sessile spikelet. [Andropogon gracilis Spreng.] 



In dry pine woods, southern peninsular Florida ; also in the West Indies. Summer. 



9. ANDROPOGON L. 



Perennial grasses, tufted or from elongated rootstocks, with flat or involute leaf -blades, 

 and spike-like racemes, disposed in pairs or sometimes in 3's or more, terminating the stem 

 or its branches, and often protruding from the side of a membranous spathe-like sheath. 

 Spikelets sometimes with a ring of short hairs at the base, in pairs at each node of the 

 articulated and frequently hairy rachis, one sessile, the other pedicellate. Sessile spikelet 

 of 4 scales, the outer 2 indurated, often pubescent, the remainder of the scales usually 

 hyaline, the fourth scale entire or 2-toothed at the apex, bearing a straight contorted or 

 spiral awn, or sometimes awnless ; palet small, hyaline. Pedicellate spikelet usually sterile 

 of 1 or 2 scales, sometimes of four scales and enclosing a staminate or more rarely a perfect 

 flower, or frequently entirely wanting, the first scale rarely short-awned. Stamens 1-3. 

 Styles distinct. Stigmas plumose. BEARD GRASS. BROOM GRASS. SAND GRASS. 



A. Pedicellate spikelet sterile, consisting of 1 or 2 scales, much smaller than the 



sessile one. 

 a. Stamen 1. 



1. Racemes usually equalling or a little shorter than the spathes, rarely 

 somewhat exceeding them (considerably exserted in some forms of 

 no. 2), the common peduncle thus concealed. 



Inflorescence oblong to oval or obovate, the branches many times di- 

 vided, the lower ones elongated, forming 1 or more corymbiform 

 masses ; upper stem-leaves usually equalling or exceeding the in- 

 florescence. 



Spathes smooth ; apex of the common peduncle of the racemes gla- 

 brous. 1. A. glomeratus. 

 Spathes very rough ; apex of the common peduncle of the racemes 



hispidulous. 2. A, corymbosus. 



Inflorescence long and narrow, commonly linear, the branches not 

 much divided nor the lower ones excessively elongated, hence 

 forming no corymbiform masses ; upper stem-leaves usually shorter 

 than the inflorescence. 

 Racemes in pairs (very rarely in 3's or 4's). 

 Sheaths not glabrous. 



Sheaths hirsute on the margins, the upper surface of the leaf- 

 blades also hirsute near the base ; hairs on the summit of 

 the internodes of the racemes rather sparse, and about 

 twice their length, 3. A. Virginicus. 



Sheaths, especially those of the innovations and their blades, 

 densely appressed-hirsute ; hairs on the summit of the 

 internodes of the racemes copious and about three times 

 their length. 4. A. longiberbis. 



Sheaths glabrous. 



Leaf-blades tuberculate-hirsute above toward the base ; hairs 

 of the racemes dense, the spikelets therefore obscurely 

 visible. 5. A. Tracyi. 



Leaf-blades not hirsute above; hairs of the racemes rather 



scant, the spikelets therefore plainly visible. 

 Branches of the inflorescence several times divided : spathes 



2-3 cm. long. 6. A. capillipes. 



Branches of the inflorescence simple : spathes 4-7 cm. long. 

 Stems slender ; basal leaf-blades narrow, 2 mm. wide or 



less, usually long and flexuous. 7. A. perangustatus. 



Stems stout ; basal leaf-blades broad and rigid, 3-6 mm. 



wide. 



Racemes in 4's (rarely in 2's or 3's) ; sheaths, at least the lower ones, 

 densely hirsute. 



