COMPOSITE. 183 



Shady hills and in ravines. Can. to Car. W. to Miss. June, July. %. Stem 

 2 5 feet high, roughly pubescent and somewhat viscid, branching. Leaves op- 

 posite or alternate, very thin, mostly 3 5-lobed at the apex. Heads small, 

 loosely paniculate ; rays white, or very pale yellow, small, obtusely 3-lobed at 

 the apex ; disk yellow. Small-flowered Polymnia. 



** Rays longer than the involucre. 



2. P. U'vedalia Linn. : stem sulcate, somewhat pubescent above ; leaves 

 sinuate-lobed, broad-ovate or deltoid, roughish ; lower subpalmate, decur- 

 rent into a winged petiole ; outer scales of the involucre oblong-ovate, ob- 

 tuse, much larger than the inner. 



Dry rich grounds. Western N. Y. and Penn. to Geor. W. to Miss. July, 

 Aug. QJ-. Stem 3 8 feet high, terete. Leaves opposite or alternate, the lower 

 very large. Heads few, large, arranged in loose panicles; rays about 10, 3- 

 toothed at the apex, bright yellow ; disk dull yellow. 



Large-flowered Polymnia. 



26. PARTHENIUM. Linn. Parthenium. 



(From the Greek napQevos ; on account of its supposed efficacy in certain 

 diseases.) 



Heads many-flowered ; ray flowers 5, pistillate, ligulate, fer- 

 tile ; those of the disk tubular, abortive. Receptacle conic or 

 cylindric, covered with membranaceous chaff. Involucre hemi- 

 spheric, in 2 series ; outer scales ovate, inner nearly orbicular. 

 Achenia obcompressed, smooth. Pappus of 2 aristate or 

 nearly orbicular scale-like processes. 



P. integrifolium Linn. : stem hirsute-pubescent ; leaves oval, rough, 

 unequally crenate-toothed, or sometimes incised; lower decurvent into a 

 petiole, upper sessile or somewhat clasping ; outer scales of the involucre 

 somewhat acute. 



Dry soil. Md. to Geor. and Ala. W. to Texas. July Sept. 1\.. Stem 

 1 2 feet high. Heads numerous, corymbed ; rays small, whitish. 



Simple-leaved Partlienium. 



27. XANTHIUM. Tmirn. Clot-weed. 



(From the Greek t<tvBos, yellow ; a color said to be produced by this plant.) 



Heads in glomerate spikes, sterile at the summit, pistillate 

 below. STERILE FL. Involucre subglobose, many-flowered, 

 with the scales in one series. Receptacle cylindric, chaffy. 

 Corolla short, 5-lobed, somewhat hairy. FERTILE FL. Involucre 

 with hooked prickles, surmounted by 1 2 beaks. Corolla 

 filiform. Stamens none. Achenia compressed, one in each 

 cell of the involucre. 



1. X. strumarium Linn.: fruit-bearing involucre oval, somewhat pubes- 

 cent ; beaks straight ; leaves cordate at base, 3 5-lobed, coarsely toothed. 



Road sides and waste places. Can. to Flor. W. to the Rocky Mountains. 

 Aug., Sept. (I)- Stem 1 3 feet high, angular, scabrous-pubescent. Leaves' 



