336 LXXV. COMPOSITE. PARTHENIUM. 



2-toothed pappus. % Stout, coarse, resinous herbs. Hds. large. Fls. 

 yellow. 



1. S. LACINIATUM. Rosin-weed. Polar Plant. 



Very rough, with white, hispid hairs; Ivs. alternate, pinnately parted, 

 lower petiolate, segments sinuate-lobed or entire ; hds. spicate, distant ; scales 

 of involucre ovate, appendaged and squarrose at apex. Western States ! to 

 Tex., producing columns of smoke in the burning prairies by its copious resin. 

 Stem 3 lOf high. Lower leaves 1 2f long, much divided, resembling those 

 of some thistles. Heads 4 8, very large, with large, yellow rays. Jl. Sept. 



2. S. TEREBINTHINACEUM. Prairie Burdock. 



St. andped. glabrous; Ivs. mostly radical, ovate and ovate-oblong, cor- 

 date, dentate-serrate, obtuse, scabrous, on long petioles ; hds. few, paniculate ; 

 scales roundish and oval, glabrous. Prairies, Western ! and Southern States. 

 Plant exuding resin. Stem 4 8f high, nearly naked and simple. Leaves 

 erect, scabrous, rigid, 1 2f long, 7 16' wide. Involucre globose. Rays 15 

 25, 1' long. Achenia narrowly 2-winged. July Sept. 



/?. pinnatifidum. T. & G. (S. pinnatifidum. Ell.} Las. more or less deeply 

 lobed or pinnatifid. 



3. S. TRIFOLIATUM. Ternate-leaved Silphium. 



St. glabrous and often glaucous, terete or 6-sided ; cauline Ivs. lanceolate, 

 acute, scabrous above, smooth below, remotely dentate, on very short petioles, 

 verticillate in 3s or 4s ; upper ones opposite ; hds. loosely cyinose, on rather 

 long peduncles ; scales broadly ovate, rather obtuse, smooth ; ach. oval, with 2 

 short teeth. Dry woods and prairies, Ohio, Sullivant ! and Southern States. 

 Stem 4 6f high. Leaves 4 6' by 12". Rays 1216, expanding about 2J'. 



4. S. INTEGRIFOLIUM. Michx. 



Scabrous ; st. quadrangular, striate, simple ; Ivs. opposite, sessile, ovate- 

 lanceolate, entire or slightly dentate ; hds. in a close corymb ; scales squarrose ; 

 ach. roundish, broadly winged, with 2 long teeth. Western States ! S. to Ga. 

 Stem very rigid, 3 7f high. Leaves rigid, broad and clasping at base, 36' 

 long, | as wide, rather variable in form. Heads middle-size. Rays 1220, 1' 

 in length. Achenia twice as large as in the preceding species. July, Aug. 



/5. ternatum. Wood. St. 6-sided; Ivs. ternately verticillate. Prairies! with 

 the common form ; apparently connecting this with S. trifoliatum, from which 

 it is nevertheless quite distinct in habit. 



5. S. PERFOLIATUM (and S. connatum. Linn.} Cup-plant. 



St. square ; Ivs. large, thin, opposite, connate-perfoliate, ovate, coarsely 

 toothed, narrowed towards the base ; hds. in a trichotomous cyme, the central 

 on a long peduncle ; scales ovate, obtuse, squarrose ; ach. broadly obovate, winged, 

 emarginate. Along streams, &c., Mich. ! to Tenn. A coarse, unattractive 

 plant, quite distinct, although variable. Stem 4 7f high. Leaves 8 14' by 

 47', the upper pairs forming a cup with their connate bases. Heads large, 

 with 1525 ravs. 



28. PARTHENIUM. 



Gr. TrapSsvos, a virgin ; from its medicinal efficacy. 



Heads many-flowered ; ray-flowers 5, somewhat ligulate, fertile ; 

 disk-flowers tubular, sterile : involucre hemispherical ; scales in 2 

 series, outer ovate, inner orbicular ; receptacle conical, chaffy ; ache- 

 nia 5, compressed, cohering with 2 contiguous paleaB. American herbs 

 with alternate leaves. 



P. INTEGRIFOLIUM. 



St. pubescent, striate, erect; Ivs. hispid-scabrous, lance-ovate, coarsely 

 dentate- crenate, coriaceous, lower petiolate, upper sessile; hds. many, tomen- 

 tose, corymbed TJ. Dry soils, Middle and Western States ! Stem rigid, 3 5f 

 high. Radical petioles If long. Leaves 4 12' long, as wide. Heads white, 

 with 5 very short, cucullate, white rays. July Sept. 



