COMPOSITAE. 981 



1. Silphium perfoliatum L. Cup-plant. Indian-cup. (I. F. f. 3865.) 

 Stem square, glabrous, or rarely somewhat hispid, branched above, or some- 

 times simple, 1-2.4 m « high. Leaves ovate or deltoid-ovate, opposite, the lower 

 abruptly contracted into margined petioles, all thin, usually scabrous on both sides, 

 or pubescent beneath, coarsely angulate-dentate, or the upper entire, the larger 12- 

 25 mm. long, 8-16 mm. wide ; heads commonly numerous, 5-7 cm. broad; rays 

 20-30, about 25 mm. long and 4 mm. wide; involucre depressed-hemispheric, its 

 outer bracts broad, ovate, ciliolate, spreading or erect; achenes obovate, emargin- 

 ate, sometimes 2-toothed. In moist soil, southern Ont. to S. Dak., south to Ga., 

 Neb. and La. Naturalized near N. Y. City. July-Sept. 



2. Silphium integrifdlium Michx. Lnti re-leaved Rosin-weed. (I. F. 

 f. 3866.) Stem glabrous, rough or sometimes hirsute, corymbosely branched above, 

 o. 6-1.5 m * hi&h- Leaves ovate to ovate-lanceolate, acute or acuminate, entire, den- 

 ticulate or remotely dentate, rough above, pubescent or glabrous beneath, 7-12 cm. 

 long, 3-5 cm. wide ; heads usually numerous, 2-5 cm. broad; involucre nearly 

 hemispheric, its outer bracts ovate or ovate-lanceolate, acute, spreading, ciliolate 

 or pubescent; rays 15-25; achenes oval or obovate, 8-10 mm. long, deeply emar- 

 ginate. On prairies, Ohio to Minn., La., Neb., Ark. and Tex. Aug. -Sept. 



3. Silphium trifoliatum L. Whorled Rosin-weed. (I. F. f. 3867.) Stem 

 glabrous, sometimes glaucous, corymbosely branched at the summit, 1-2 m. high. 

 Leaves lanceolate or oblong-lanceolate, acuminate at the apex, narrowed at the 

 base, rough or roughish above, pubescent or nearly glabrous beneath, entire or den- 

 ticulate, 7-17 cm. long, 1-4 cm. wide; heads several or numerous, 4-5 cm. 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, Penn. to Ohio, Va. and Ala. July- 

 Oct. 



4. Silphium Asteriscus L. Starry Rosin-weed. (I. F. f. 3868.) Stem 

 0.6-1.2 m. high, usually purple. Leaves ovate, ovate-oblong, or lanceolate, acute 

 or obtusish, sessile, somewhat clasping, or the lower narrowed into short petioles, 

 dentate, or the upper entire, 5-12 cm. long, 1-2.5 cm. wide; heads commonly few, 

 3-5 cm. broad; rays 12-15; involucre hemispheric, its bracts mostly hispid, orbic- 

 ular, ovate or oblong, obtuse; achenes oval or obovate, narrowly winged, 2-toothed. 

 In dry soil, Md. to Tenn. and Mo., south to Fla. and La. June-Sept. 



5. Silphium Gatesii Mohr. Gates' Rosin-weed. Stems 0.6-1.5 m - tall, 

 hispid, simple or sparingly branched above. Leaves alternate, broadly linear to 

 oblong-lanceolate or lanceolate, 5-14 cm. long, acute, remotely serrate, rough- 

 pubescent, the lower ones short-petioled; heads showy; involucre campanulate, 

 barely I cm. high, the bracts mainly triangular to lanceolate, hirsute or pubescent, 

 the outer acute or short-acuminate; ray-flowers several, the ligules yellow, 12-20 

 mm. long; achenes suborbicular or broader than high, the teeth when present 

 separated by a broad sinus. In dry soil, Mo. to Tenn. and Ala. May-Aug. 



6. Silphium laciniatum L. Compass-plant. Pilot-weed. (I. F. f. 3869.) 

 Rough or hispid, very resinous; stem 2-5 m. high; basal leaves pinnatifid or 

 bipinnatifid, long-petioled, 3 dm. long or more, the lobes oblong or lanceolate ; stem- 

 leaves alternate, vertical, their edges tending to point north and south, sessile, or the 

 lower short-petioled, the upper cordate-clasping at the base; heads 5-12 cm. broad, 

 the peduncles bracted at the base ; rays 20-30, 25-35 mm. long ; involucre nearly 

 hemispheric, its bracts large, rigid, lanceolate or ovate, very squarrose ; achenes 

 oval, about 12 mm. long, the wing broader above than below, notched at the apex, 

 awnless. On prairies, Ohio to S. Dak., Ala., La., Kans. and Tex. July-Sept. 



7. Silphium terebinthinaceumjacq. PrairieDock. (I. F. f. 3870.) Stem 

 glabrous or nearly so, branched and scaly above, 1-3 m. high. Leaves coriaceous, 

 ovate, mostly long-petioled, acute at the apex, cordate at the base, rough on both 

 sides, often 3 dm. long and 15 cm. wide, sharply dentate ; heads numerous, 

 4-7 cm. broad; involucre hemispheric, its bracts obovate-oblong, erect, glabrous 

 or minutely pubescent ; rays 12-20 ; achenes obovate, narrowly winged, slightly 

 2-toothed and emarginate at the apex. On prairies and in dry woods, southern 

 Ont. and Ohio to Minn., Iowa and La. July-Sept. 



Silphium terebinthiniceum pinnatifidnm (Ell.) A. Gray. Leaves laciniate or pin- 

 natifid. Ohio to Tenn. and Ga. 



