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. Scales of the involucre 

 leafy, imbricated in several rows ; the innermost smallest, chaff-like. Keceptacle 

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

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

 der. Pappus none, or represented by the two teeth of the achenia. Tall resinous 

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

 ers in corymbose panicles. 



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

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



1. S. laciniatum, 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. gummifcrum, Ell.) Prairies of Alabama, and 

 westward. July and August. Stem 6 - 8 high. Lowest leaves 1 - 2 long. 

 Heads l^'-2' in diameter. 



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

 hairy, 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. pinnatifidum, Ell., 

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

 ward. July -Sept. Stem 4 -8 high. Eadical 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, corymbosely 

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

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

 gularly toothed or lobed.) Var. MICHAUXII, Ton-. & Gray. Leaves deeply 

 pinnatifid or tern ately divided; the divisions lobed or toothed. Var. OVATIFO- 

 LIUM, 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, or whorled. 

 - Stems terete. 



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

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

 3 -4 in a whorl ; heads small, loosely panicled ; scales of the involucre ovate or 

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

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

 and northward. July - Sept. Stem 4 - 6 high. Leaves 4' - 6' long. 



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

 alternate, or the lower ones sometimes 3 in a whorl, lanceolate or oblong, toothed, 



