220 co.MrosiT/E. (compositk 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, iml)ricated in several rows ; the innermost smallest, chaff-like. Receptaclo 

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

 flat, broadly winged, 2-toothed or cmarginatc 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 jjaniclcs. 



* Stems tenle, nearly naked: leaves alternate; the lowest large, seirate or variouslij 

 lohecl, 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 tootlied ; heads large, spicate or racemose; scales of the invo- 

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

 ohovate, cmarginate. — Varies with the more numerous sessile and clasping 

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

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

 Heads li'-2' in diameter. 



y^ 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, emarginatc 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. Padical leaves 2° long. Heads 1' 

 wide. 



3. S. COmpositum, IMichx. Smooth; leaves cordate-ovate or rcniform, 

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

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

 deeply cmarginatc; rays 6- 10. (S. tercbintliinaceum, £■//., leaves rcniform, an- 

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

 pinnatifid or ternately divided; the divisions lobed or toothed. — Var ovatifo- 

 mi:m. Ton'. & Gray. Leaves ovate, angularly toothed. — Sandy open woo<ls, 

 Florida to North Carolina. July - Sept. — Stem 3° - 6° high. Leaves 6' - 1 2' 

 long. Heads ^' in diameter. 



* * Stems leafg : leaves undivided, alternate, opposite, or whorled. 

 -t- Stems terete. 



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

 serrate, on short bri<tly petioles ; the upper ones alterinite or opposite ; the lower 

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

 oval, fringed on the mapjins; achenia oltlong-ohovate, 2-toothed. (S. ternatuni 

 and S. utro|)urpun 11(11, UVW.) — Open woods along the mountains of Georgia, 

 and northward. July - Scjit. — Stem 4° - 6° high. Leaves 4' - 0' long. 



5. S. AsteriscUS, !>• Stem smooth or hirsute ; leaves rouirh, opposite or 

 alternate, or I In; !(nver ones somctiines 3 iu a whorl, lanceolate or oblong, tootlied. 



