220 COMPOSITE. (composite family.) 



32. SILPHIUM, L. 



Heads many-flowered ; the rays numerous, pistillate, fertile, in a single row. 

 Disk-flowers cylindrical, sterile ; the style undivided. Seales of the involucre 

 leafy, imbricated in several Hows; the innermost smallest, chart-like. Receptacle 

 small, with linear acutish chaff. Fertile aclienia in 3-4 rows, round or obovate, 

 flat, broadly winged, 2-toothcd or emarginate at the apex; the sterile ones slcn- 

 di r. Pappus none, or represented by the two teeth of the achenia. — Tall resinous 

 herbs, with alternate opposite or whorkd leaves, and large heads of yellow flow- 

 ers in corymbose panicles. 



* Stems terete, nearly naked: leaves alternate; the lowest large, serrate or variously 

 Imbed, long-petioled ; the others small and scattered. 



1. S. laeiniatum, L. Stem hispid or smooth; leaves very rough or his- 

 pid, on clasping petioles, pinnately parted ; the divisions oblong or lanceolate, 

 acute, lobed or toothed ; heads large, spicate or racemose ; scales of the invo- 

 lucre ovate, tapering into a long and spreading point, ciliate ; achenia round- 

 obovate, emarginate. — Varies with the more numerous sessile and clasping 

 leaves less deeply parted. (S. gummiferum, Ell.) — Prairies of Alabama, and 

 westward. July and August. — Stem C° - 8° high. Lowest leaves 1° - 2° long. 

 Heads l£'-2' in diameter. 



2. S. terebinthinaceum, L. Stem smooth, naked above ; leaves rouprh- 

 bairv, undivided, cordate-oval or oblong, coarsely serrate, on slender petioles ; 

 heads small, loosely panicled ; scales of the involucre oval or obovate, obtuse, 

 smooth; achenia obovate, emarginate or 2-toothed. (S. pinnatitidum, Ell., 

 leaves pinnatifid.) — Open woods in the western districts of Georgia, and west- 

 ward. July -Sept. — Stem 4° -8° high. Radical leaves 2° long. Heads 1' 

 wide. 



3. S. compositum, Michx. Smooth; leaves cordate-ovate or reniform, 

 angularly toothed or variously lobed, long-petioled ; heads small, corymbosery 

 panicled; scales of the involucre obovate or oblong, obtuse ; achenia roundish, 

 deeply emarginate; rays 6- 10. (S. terebinthinaceum, Ell., leaves reniform, an- 

 gularly toothed or lobed.) — Var. Miciiauxii, Torr. & Gray. Leaves deeply 

 pinnatifid or temately divided; the divisions lobed or toothed. — Var <>v aim <>- 

 i.tiM, Torr. & Gray. Leaves ovate, angularly toothed. — Sandy open woods, 

 Florida to North Carolina. July - Sept. — Stem 3° - 6° high. Leaves 6' - 12' 

 long. Heads £' in diameter. 



* * Stems leafy: leaves undivided, alternate, opposite, orwhorled. 

 •*- Stems ten te. 



4. S. trifoliatum, L. Stem smooth; leaves rough, lanceolate, Blightly 

 serrate, on short bristly petioles ; the upper ones alternate or opposite ; the lower 



3-4 in a vrhorl ; heads small, loosely panicled ; Bcales of the involucre oval : 



oval, fringed on the margins; achenia oblong-obovate, 2-toothed. (8 ternatum 

 and S. atropurpureum, WiUd.) — Open woods along the mountains of Georgia, 



and northward. July - Sept, — Stem 4° - C° high. Leaves 4' - 0' long, 



5. S. AstcrisciiB, L. Stem smooth or hirsute ; leaves rough, opposite or 

 alternate, or the lower ones sometimes •'! in a whorl, lanceolate or oblong, toothed, 



