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 ; Ms. 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—21' 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. and ped. 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. 



/3. pinnatifiduvi. T. & G. (S. pinnatifidum. Ell.) Lvs. more or less deeply 

 lobed or pinnatifid. 



3. S. TRiFOLiATUM. Temate-leavcd Silphium. 



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

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

 verticillate in 3s or 4s ; vpper ones opposite ; hds. loosely cymose, 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 1—2": Rays 12—16, expanding about 2i', 



4. S. INTEGRIFOLIUM. Michx. 



Scabrous; st. quadrangular, striate, simple; lvs. 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, 3 — 6' 

 long, i as wide, rather variable in form. Heads middle-size. Rays 12 — 20, 1' 

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



i3. tcrnatiim. Wood. St. 6-sicied; lvs. 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 ; lvs. large, thin, opposite, connate-perfoliate, ovate, coarsely 

 toothed, narrowed towards the base ; hds. in a trichotomous C)Tne, the central 

 on a long peduncle ; scales ovate, obtuse, squarro.se ; 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 

 4 — 7', the upper pairs forming a cup with their connate bases. Heads large, 

 with 15 — 25 ravs. 



28. PARTHENIUM. 



Gr. Tap^cvos, 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, chafiy ; ache- 

 nia 5, compressed, cohering with 2 contiguous palese. — American herbs 

 with alternate leaves. 



P. INTEGRIFOLIUM. 



Sf. pubescent, striate, erect; lvs. hispid-scabrous, lance-ovate, coarsely 

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

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

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

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



