1244 CAEDUACEAE 



dentate-serrate : heads corymbose : involucres about 1 cm. high ; bracts ovate-lanceolate to 

 suborbicular, oblong or oblong-cuneate, merely ciliate, the outer ones acute, the inner ob- 

 tuse : ray-flowers several ; ligules yellow, 2-3 cm. long : acbenes obovate to oval, 6-8 mm. 

 long, winged, the teeth rounded, or the sinus nearly obsolete. 

 In sandy soil, South Carolina to Florida and Alabama. 



18. Silphium Simpsonii Greene. Stems 9-12 dm. tall, less densely pubescent above 

 than below, often sparingly branched above. Leaves whorled or opposite, or alternate above ; 

 blades various, those of the basal leaves oblong to lanceolate-oblong, 10-15 cm. long, on 

 short-margined petioles, those of the upper part of the stem ovate or broadly ovate, 3-10 

 cm. long, sessile and half-clasping by broad bases, all coarsely crenate-serrate or slightly 

 repand : heads few : involucres 2-2.5 cm. broad ; bracts suborbicular to ovate, merely cilio- 

 late : ray-flowers 12-16; ligules yellow, 2.5-3 cm. long: achenes obovate or orbicular-ob- 

 ovate, 10-13 mm. long. 



In sandy pine lands, southern peninsular Florida. Summer. 



19. Silphium Asteriscus L. Stems 6-15 dm. tall, corymbose above, scabrous-pu- 

 bescent. Leaves opposite or sometimes alternate on the upper part of the stem ; blades 

 oblong to oblong-lanceolate or ovate-lanceolate, more or less distinctly serrate, those of 

 the lower leaves petioled : heads showy : involucres campauulate, about 1 cm. high : bracts 

 oblong-lanceolate to oval and oblong, obtuse, or the outer ones acutish, merely ciliate : ray- 

 flowers 11-15 ; ligules 1.5-2 cm. long : achenes oval or obovate-oval, 7-9 mm. long, sur- 

 mounted by acute teeth. 



In dry soil, Virginia to Ohio, Florida and Mississippi. Summer and faU. 



20. Silphium angustum (A. Gray) Small. Stems 6-12 dm. tall, simple or sparingly 

 branched above, scabrous-pubescent. Leaves mostly alternate, few on the upper part of 

 the stem ; blades narrowly oblong or narrowly oblong-lanceolate, 2-10 cm. long, repand- 

 serrate or nearly entire, the upper ones sessile or partly clasping : heads solitary or few, 

 showy : involucres campauulate, barely 1 cm. high ; bracts ovate to orbicular or broadly 

 spatulate, ciliate, the outer acute, the inner obtuse : ray-flowers several ; ligules yellow, 

 2-2.5 cm. long: achenes broader than high, 9-19 mm. broad, surmounted by short teeth. 



In sandy soil, western Florida. Summer. 



21. Silphinm Gat^sii Mohr. Stems 6-15 dm. tall, hispid, simple or sparingly 

 branched above. Leaves alternate ; blades broadly linear to oblong-lanceolate or lanceo- 

 late, 5-14 cm. long, acute, remotely serrate, scabrous-pubescent, the lower ones short- 

 petioled : heads showy : involucres campanulate, barely 1 cm. high ; bracts lanceolate to 

 ovate and oblong , hispid, the outer acute and short-acuminate, the inner obtuse: ray- 

 flowers several ; ligules yellow, 12-20 mm. long]: achenes suborbicular or broader than 

 high, the teeth forming a broad sinus. 



In dry soil, Missouri to Tennessee and Alabama. Spring and summer. 



22. Silphium scab6rrimum Ell. Stems 9-15 dm. tall, glabrous, or sparingly pubes- 

 cent above. Leaves opposite or the upper ones sometimes alternate : blades oblong-lance- 

 olate, ovate-lanceolate or narrowly ovate, 10-20 cm. long, or rather shorter high up on the 

 stem, acute or somewhat acuminate, sharply serrate, scabrous on both sides ; petioles about 

 J as long as the blades near the base of the stem, gradually shorter above : heads usually 

 few, showy : involucres campanulate, about 1 cm. high ; bracts oblong-lanceolate to ovate or 

 oblong, not conspicuously pubescent, but ciliate, obtuse or the outer ones acutish, the inner 

 with recurved tips : ray-flowers several ; ligules about 1.5 cm. long, yellow : achenes sub- 

 orbicular, 5-7 mm. broad, broadly winged, with a deep notch at the apex. 



In open woods and fields, Virginia and Tennessee to Georgia and Mississippi. Summer. 



23. Silphium integrifolium Michx. Stems 8-15 dm. tall, rough-pubescent, 4-angled 

 or striate-ridged. Leaves opposite or mainly so ; blades ovate to broadly lanceolate, quite 

 uniform in size, 7-12 cm. long, scabrous on both sides, acute, often shallowly toothed on 

 the lower part of the stem, mostly entire above : heads in rather open corymbs : involucres 

 1-1.5 cm. high ; bracts more or less pubescent, the outer triangular-ovate to lanceolate, 

 acute, the inner broader, obtuse : ray-flowers 15-23 ; ligules bright yellow, 2-3 cm. long : 

 achenes narrowly obovate, about 1 cm. long, broadly winged only near the top, the broad 

 teeth forming a V-sliaped sinus. 



On plains and prairies, Wisconsin to Illinois, Mississippi and Texas. Summer and fall. 



24. Silphium asp6rrimum Hook. Stems 7-14 dm. tall, closely scabrous-pubescent, 

 branching above. Leaves pubescent like the stem, the lower opposite, the upper alternate ; 

 blades ovate to lanceolate, 5-10 cm. long, acute, entire or undulate, sessile and often partly 

 clasping: heads showy, on densely white-bristly peduncles: involucres 1-1.5 cm. high; 



