GENUS SI. THISTLE FAMILY. 461 
3. Silphium trifoliatum L. Whorled 
Rosin-weed. Fig. 4423. 
Silphium trifoliatum L. Sp. Pl. 920. 1753. 
Stem glabrous, sometimes glaucous, corym- 
bosely branched at the summit, 4°-7° high. 
Leaves lanceolate or oblong-lanceolate, the 
middle ones almost always whorled in 3’s or 
4’s, acuminate at the apex, narrowed at the 
base and usually somewhat petioled, rough 
or roughish above, pubescent or nearly gla- 
brous beneath, entire or denticulate, 3-7’ long, 
3-14’ wide;. heads several or numerous, 13’-2’ 
broad; involucre hemispheric, its outer bracts 
ovate or oval, acute or obtuse, glabrous or 
slightly pubescent, ciliolate; rays 15-20; achenes 
oval-or obovate, narrowly winged, emarginate, 
sharply 2-toothed. 
In woods, Pennsylvania to Ohio, Ontario, Vir- 
ginia and Alabama. July—Oct. 
4. Silphium Asteriscus L. Starry Rosin- 
weed. Fig. 4424. 
Silphium Asteriscus L. Sp. Pl. 920. 1753. 
Stem hispid-pubescent, simple or branched above, 
2°-4° high, usually purple. Leaves nearly all 
alternate, ovate, ovate-oblong, or lanceolate, acute 
or obtusish, sessile, somewhat clasping, or the 
lower narrowed into short petioles, dentate, or 
the upper entire, 2’-5’ long, 4’-1’ wide; heads 
commonly few, 1’-2’ broad; rays 12-15; invo- 
lucre hemispheric, its bracts mostly hispid, ovate 
to oblong, acute or obtuse, squarrose; achenes 
oval or obovate, narrowly winged, 2-toothed. 
In dry soil, Maryland to Tennessee and Missouri, 
south to Florida and Louisiana. June-Sept. 
5. Silphium laciniatum L. Compass- 
plant. Pilot-weed. Fig. 4425. 
Silphium laciniatum L. Sp. Pl. 919. 1753. 
Rough or hispid, very resinous; stem 6°-12° 
high; basal leaves pinnatifid or bipinnatifid, 
long-petioled, 1° long or more, the lobes ob- 
long or lanceolate; stem leaves alternate, ver- 
tical, their edges tending to point north and 
south, sessile, or the lower short-petioled, the 
upper cordate-clasping at the base, gradually 
smaller and less divided; heads several or 
numerous, sessile or short-peduncled, 2’—5’ 
broad, the peduncles bracted at the base; rays 
20-30, 1’-2’ long; involucre nearly hemispheric, 
its bracts large, rigid, lanceolate or ovate, very 
squarrose; achenes oval, about 6” long, the 
wing broader above than below, notched at 
the apex, awnless. 
On prairies, Ohio to South Dakota, south to 
Alabama, Louisianaand Texas. Turpentine-weed, 
polar-plant, rosin-weed. July—Sept. 
