462 



COMPOSITAE. 



6. Silphium terebinthinaceum Jacq. 



Prairie Dock. Prairie Burdock. 



Fig. 4426. 



Silphium terebinthinaceum Jacq. Hort. Vind. 

 i: pi. 43- 1770. 



S. pinnatifidum Ell. Bot. S. C. & Ga. 2 : 462. 

 1824. 



Silphium terebinthinaceum pinnatifidum A. 

 Gray, Man. 220. 1848. 



Stem glabrous or nearly so, branched 

 and scaly above, 4-io high. Leaves all 

 basal or nearly so, coriaceous, ovate, mostly 

 long-petioled, acute at the apex, cordate 

 at the base, rough on both sides, often 12' 

 long and 6' wide, sharply dentate, laciniate 

 or pinnatifid ; heads numerous, i~3' broad, 

 borne on glabrous peduncles ; involucre 

 hemispheric, its bracts ovate-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 On- 

 tario and Ohio to Minnesota, south to Georgia, 

 Iowa and Louisiana. Rosin-plant. July-Sept. 



7. Silphium reniforme Raf. Kidney- 

 leaved Silphium. Fig. 4427. 



Silphium reniforme Raf. ; Nutt. Trans. Am: 

 Phil. Soc. (II) 7 : 342. 1840. 



S. compositum reniforme T. & G. Fl. N. A. 2 : 

 276. 1842. 



Stem scape-like, 3-6 tall, glabrous or 

 nearly so, corymbosely branched above. 

 Leaves mostly basal, broadly ovate to reni- 

 form, 4'-! 5' long, obtuse or abruptly point- 

 ed, coarsely dentate, deeply cordate at the 

 base, long-petioled ; heads numerous, about 

 i' broad, the peduncles glabrous; involucre 

 campanulate, the bracts ovate or broadly 

 oblong to narrowly oblong or oblong-spatu- 

 late, obtuse ; rays several, yellow ; achenes 

 suborbicular or orbicular-obovate, 3$" long, 

 the wings prolonged enough to form a shal- 

 low apical sinus. 



In dry or stony soil, mountains of Virginia 

 and North Carolina. July-Aug. 



Silphium compositum Michx., a related 

 southern species with pedately parted leaves, 

 is reported as observed in southern Virginia. 



52. CHRYSOGONUM L. Sp. PI. 920. 1753. 



Pubescent perennial herbs, with opposite and basal petioled leaves, and slender-peduncled- 

 axillary and terminal, rather large heads of both tubular and radiate, yellow flowers. Invo- 

 lucre hemispheric, its bracts in 2 series of 5, the outer large, obovate or spatulate, foliaceous, 

 the inner oval, firm, each subtending a pistillate ray-flower. Receptacle chaffy, each scale 

 subtending and partly enclosing a perfect but sterile tubular flower with a 5-tooth,ed corolla. 

 Anthers nearly entire at the base. Achenes obovate, compressed, their margins acute, not 

 winged, i-nerved on the back, i-2-ribbed on the inner side. Pappus a short half-cup-shaped 

 crown. [Greek, golden-knee.] 



A monotypic genus of eastern North America. 



