182 COMPOSITE. 



IV. SENECIONIDE.E. Style of the perfect flowers cylindrical ; its 

 branches linear, fringed at the point, generally truncate, but sometimes 

 extended beyond the fringe into a short cone or appendage. 



24. SILPHIUM. Linn. Silphium. 



(From Silpki, the name of a medicinal plant of Africa, transferred to this genus 

 by Linnaeus.) 



Heads many-flowered ; ray flowers numerous, ligulate, pis- 

 tillate ; the ligules in one series, elongated, the fruit in several 

 series ; those of the disk with a very short tube, hairy above, 

 sterile. Receptacle somewhat convex, chaffy. Involucre cam- 

 panulate, imbricate ; the scales loose and leafy at the summit. 

 Achenia of the ray obcompressed, surrounded with a wing 

 which is notched or toothed at the top ; those of the disk abor- 

 tive, with an obsolete crown-like pappus. 



1. <S. trifoliatumLinn.: stem terete, slightly angled, smooth; leaves 3 4 

 in a whorl, ovate-lanceolate, unequally toothed and serrate, scabrous on 

 the upper surface ; lower petioled, upper nearly sessile and sometimes oppo- 

 site ; heads loose, corymbose or paniculate. & trifoliatum and S. terna- 

 tum Pursh. 



Dry woods. Near the Falls of Niagara. Dr. Eddy. Md. to Car. W. to Ohio. 

 Aug. Oct. 1].. Stem 4 6 feet high, slightly angled, purplish. Heads rather 

 f-mall, in a loose terminal corymb ; rays 15 18, bright yellow, long. 



Three-leaved Sylphium. 



2. S. perfoliatum Linn. : stem square, smooth, the branches sometimes 

 terete ; leaves opposite ; lower deltoid-ovate, coarsely serrate, on winged 

 petioles 5 upper connate-perfoliate, nearly entire ; heads trichotomously 

 corymbose, the central one on a long peduncle. /S. connatum Mich. 



Banks of streams. Penn. ? to Car. W. to Miss. Aug. 1|~ Stem 5 6 feet 

 high. Leaves very large, the lower somewhat cordate. Heads large; rays 

 1530, yellow. Perfoliate Silphium. 



25. POLYMNIA. Linn. Polymnia. 

 (Said to be named after TloXu/jj/ta, one of the Muses.) 

 Heads many-flowered ; the ray flowers pistillate, ligulate, in 

 one series ; those of the disk tubular, sterile. Receptacle flat, 

 chaffy. Involucre double ; the outer scales 4 5, large and 

 leafy ; the inner ones numerous, shorter, surrounding the smooth 

 achenia. Pappus none. 



* Rays shorter than the involucre. 



1. P. Canadensis Linn.: viscid-pubescent; leaves angulate and hastate- 

 lobed, denticulate, acuminate, the lower deeply pinnatifid or lyrate ; scales 

 of the involucre ovate, acuminate, ciliate, the outer ones a little larger. 



