1242 CARDUACEAE 



oval, suborbicular or rhombic ciliate bodies and involute curved or recurved acuminations : 

 ray-flowers numerous ; ligules white, 2-2.5 cm. long : achenes oblong-oval, 15-18 mm. long, 

 the wings prolonged above, the sinus U-shaped. 

 In limestone soil, Texas. Summer. 



3. Silphium lacin&tum L. Stems stout, 1-3.5 m. tall, coarsely hispid. Leaves 

 mainly basal ; blades 1-4 dm. long, the segments lanceolate to linear, entire or pinnatifid, 

 the dilated bases of the petioles often pinnatifid : heads showy : involucres 2-2.5 cm. high ; 

 bracts broadly lanceolate or ovate-lanceolate, 2. 5-4 cm. long : ray -flowers numerous ; ligules 

 yellow, 3-5. 5 cm. long : achenes oval to suborbicular, about 10 mm. long, narrowly winged, 

 each with a shallow notch at the top. 



On prairies, Ohio to South Dakota, Alabama and Texas. Summer. COMPASS-PLANT. 



4. Silphium venosum Small. Stems scape-like, 8-12 dm. tall, glabrous or nearly so, 

 glaucous. Leaves mainly basal ; blades ovate to oblong, 1-3 dm. long, conspicuously red- 

 veined, pinnately parted, the segments linear to linear-oblong, coarsely and irregularly 

 toothed or incised ; petioles about as long as the blades, dilated at the base: heads- few, 

 showy, corymbose : involucres campanulate, about 1 cm. high ; bracts broadly oblong to 

 orbicular-oval, rounded at the apex, ciliolate : ray-flowers several ; ligules yellow, 1-1.5 cm. 

 long : achenes suborbicular, about 1 cm. long, the wings produced above, thus forming a 

 narrow U-shaped sinus. 



In sand, southeastern Georgia. Spring and summer. 



5. Silphium compdsitum Michx. Stems 1-2 m. tall, scape-like, more or less 

 branched above. Leaves mainly basal and on the lower part of the stem ; blades mostly 

 pedately parted, 1-3 dm. long, not conspicuously veined ; petioles longer than the mid- 

 nerves : heads often numerous : involucres campanulate, about 1 cm. high ; bracts ovate 

 to broadly oblong, obtuse, ciliolate, dull without, lustrous within : ray-flowers several ; 

 ligules bright yellow, 14-20 mm. long : achenes cuneate-obovate, 5-6 mm. broad. 



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



6. Silphium ovatlfolium (T. & G.) Small. Stems 0.5-2 m. tall, glabrous or 

 nearly so, branching above, rather scape-like. Leaves mainly basal ; blades ovate to ob- 

 long-ovate, 1-3 dm. long, mainly pinnately parted or pinnatifid, or irregularly and coarsely 

 toothed and incised on the upper part of the stem ; petioles longer than the midnerves on 

 the lower part of the stem : involucres campanulate, about 1 cm. high : bracts oblong, oval 

 or oblong-ovate, rounded at the apex : ray -flowers several ; ligules yellow, 1-1.5 cm. long: 

 achenes suborbicular, about 10 mm. broad. 



In sandy soil, southern Georgia and Florida. Spring and summer. 



7. Silphium renifdrme Kaf. Stems scape-like, 1-2 m. tall, glabrous or nearly so, 

 corymbosely branched above. Leaves mostly basal ; blades ovate to reniform, 1-3.5 dm. 

 long, obtuse, coarsely dentate, deeply cordate at the base ; petioles longer than the blades 

 on the lower part of the stem : involucres campanulate, 5-7 mm. high ; bracts ovate or 

 broadly oblong to narrowly oblong or oblong-spatulate, obtuse : ray-flowers several ; ligules 

 yellow, 1-1.5 cm. long : achenes suborbicular or orbicular-obovate, 7 mm. long; wings pro- 

 longed enough to form a shallow sinus. 



In dry or stony soil, mountains of North Carolina. Summer. 



8. Silphium nimicifolium Small. Stems 4-8 dm. tall, reddish purple, scape-like, 

 corymbose above. Leaves mainly basal ; blades leathery, oblong to oblong-ovate, 1-1. 5 

 long, rounded at the apex, repand-undulate, smooth, red-veined above, rather cuneate 

 at the base ; petioles shorter than the blades, dilated and sheathing at the base : involucres 

 hemispheric, fully 2 cm. broad ; bracts varions, the outer suborbicular, broader than long, 

 the inner oblong, rounded at apex: ray-flowers several; ligules yellow, 1.5-2 cm. long: 

 achenes oblong-obovoid, 9-10 mm. long, narrowly winged and notched at the apex. 



In dry sterile soil, near Knoxville, Tennessee. Summer and fall. 



9. Silphium terebinthinaceum Jacq. Stems scape-like, 1-3 m. tall, branching near 

 the top. Leaves mainly basal ; blades ovate, oblong-ovate or oblong, 1-6 dm. long, den- 

 tate, with more or less prolonged teeth, cordate at the base : heads showy, relatively few : 

 involucres broadly campanulate, 1-1.5 cm. high ; bracts various, the outer ovate or oval, 

 the inner oblong, much broader than the outer, all obtuse and longer than broad : ray- 

 flowers 15-25 ; ligules yellow, 2-3 cm. long : achenes cuneate, 8-9 mm. long, with sharp 

 teeth at the top. 



In open grounds, Michigan to Iowa, Ohio, Georgia and Louisiana. Summer and fall. 



10. Silphium pinnatifidum Ell. Stems 0.5-3 m. tall, scape-like, often widely 

 branched above, pubescent. Leaves mainly basal ; blades pinnatifid or pinnately parted, 





