CARDUACEAE 1243 



the segments entire or incised, or rarely some of them merely undulate ; petioles shorter 

 than the blades : heads showy : involucres hemispheric, about 1 cm. high ; bracts various, 

 the outer suborbicular, the inner oblong, about twice as long as the outer, all obtuse : ray- 

 flowers 12-20 ; ligules yellow, 1.5-2 cm. long : achenes cuneate to oblong-cuneate, 9-10 

 mm. long, without teeth at the top. 



In open grounds, Ohio to Georgia and Alabama. Summer. 



11. Silphium brachi&tum Gattinger. Stems 1-2 m. tall, square, smooth and glau- 

 cous, dichotomous above : leaf-blades scabrous above, 8-15 cm. long, the lower ones trian- 

 gular-hastate, truncate or subcordate at the base, repand-toothed, acute, with petioles $ as 

 long as the blades, conspicuously ciliate, the upper ovate-lanceolate to lanceolate, entire or 

 nearly so : involucres campanulate, about 1 cm. high ; bracts ovate to oblong, obtuse, 

 ciliate, the tips often somewhat spreading: ray-flowers several ; ligules yellow, 1-1.5 cm. 

 long : achenes suborbicular, 6.5-7.5 mm. broad, narrowly winged and notched at the apex. 



On hillsides, Cumberland Mountains, Tennessee. Summer. 



12. Silphium trifoliatum L. Stems 1-2 m. tall, smooth, glabrous and glaucous, often 

 widely branched above. Leaves in whorls of 3, or rarely opposite or alternate above ; 

 blades lanceolate to linear-lanceolate, 8-10 cm. long, remotely serrate or nearly entire, 

 acute or slightly acuminate, scabrous on both sides : heads often numerous, rather showy : 

 involucres campanulate, about 1 cm. high ; bracts oblong-lanceolate to ovate and oblong, 

 ciliate, the outer acutish, the inner obtuse: ray-flowers few; ligules yellow, 2-2.5 cm. 

 long: achenes 5 obovate or oblong-obovate, 8-10 mm. long, narrowly winged, with 2 acute 

 teeth. 



On hillsides, Pennsylvania and Ohio to Alabama. Summer. 



13. Silphium glabnun Eggert. Stems 9-15 dm. tall, smooth, regularly leafy to the 

 top, simple or 'sparingly branched above. Leaves opposite or the upper ones sometimes 

 alternate ; blades ovate-lanceolate -to lanceolate, 8-20 cm. long, acute or short-acuminate, 

 remotely dentate, smooth and glabrous except along the margins : heads few : involucres 

 campanulate, about 1 cm. high ; bracts oblong-lanceolate to ovate or oblong, obtuse, ciliate : 

 ray -flowers several ; ligules yellow, 2-2.5 cm. long : achenes obovate, 7 mm. long, with 

 narrow wings and short acute teeth. 



In dry soil, North Carolina and Tennessee to Alabama and Georgia. Summer and fall. 



14. Silphium confertifolium Small. Stems 1-6 dm. tall, smooth and glabrous, 

 simple or with few ascending branches above. Leaves mainly on the lower part of the 

 stem, and there'approximated or crowded ; blades firm, oblong to ovate-lanceolate, 6-12 

 cm. long, acute or cuspidate, ciliate, nearly entire or shallowly toothed, slightly scabrous 

 except near the center : involucres campanulate, 7-10 mm. high ; bracts broadly oblong, or 

 oblong-obovate, obtuse, merely ciliate, with spreading or recurving tips at maturity : ray- 

 flowers several ; ligules yellow, 1.5-2 cm. long : achenes orbicular-cuneate, 6-7 mm. long, 

 margined, with 2 ascending teeth. 



In dry soil, Alabama. Summer and fall. 



15. Silphium speciosum Nutt. Stems 6-12 dm. tall, smooth, glabrous, glaucous, 

 rather corymbosely branched above, the branches sometimes pubescent. Leaves mostly op- 

 posite ; blades broadly lanceolate to oblong- or ovate-lanceolate or sometimes ovate, 6-16 

 cm. long, acute or slightly acuminate, usually shallowly toothed, partly clasping by a 

 rounded or somewhat cordate base, scabrous above, smooth beneath : heads rather crowded 

 or approximate : involucres 12-15 mm. high ; bracts more or less pubescent, the outer 

 broadly lanceolate to triangular, the inner broadly ovate or nearly reniform : ray-flowers 

 14-26 ; ligules bright yellow, 2-2.5 cm. long : achenes oval, 11-13 mm. long, rather nar- 

 rowly winged, each with a broad sinus at the top. 



On plains and prairies, Missouri and Kansas to Texas. Summer and fall. 



16. Silphium Elliottii Small. Stems 8-13 dm. tall, scabrous or nearly smooth in age, 

 corymbosely branched above. Leaves alternate, or few sometimes opposite ; blades lanceo- 

 late to broadly oblong-lanceolate or rarely oval, 6-12 cm. long, entire, or occasionally with 

 few indistinct teeth, conspicuously ciliate ; petioles of the lower leaves more conspicuously 

 ciliate than the blades : heads showy, often in terminal clusters : involucres 10-12 mm. 

 high ; bracts oblong to suborbicular and obovate, merely ciliate, obtuse, or the outer acutish : 

 ray -flowers several ; ligules 1.5-2 cm. long, yellow : achenes obovate or oblong-obovate, 6-8 

 mm. long, narrowly winged, each with a U-shaped sinus. 



In dry soil, North Carolina to Alabama. Summer. 



17. Silphium dentatum Ell. Stems 6-15 dm. tall, glabrous or sparingly pubescent 

 near the top. Leaves opposite or the upper rarely alternate, or in whorls of 3 ; blades ob- 

 long to lanceolate or ovate-lanceolate, 5-15 cm. long, acute, commonly coarsely dentate or 



