240 COMPOSITE. (COMPOSITE FAMILY.) 



34. POLYMNIA, L. 



Heads radiate, many-flowered ; the rays pistillate, iu a single row ; those of 

 the disk tubular, 5-toothed, sterile. Scales of the involucre in two rows ; the 

 outer leafy, spreading ; the inner smaller, meinhrauaceous, clasping the obo- 

 void fertile acheuia. Receptacle chaffy. Pappus none. Coarse branching 

 perennial herbs, with angular or lobed leaves, and heads of yellow flowers in 

 corymbose panicles. 



1. P. Canadensis, L. Viscid-pubescent; lowest leaves opposite, peti- 

 oled, piuuatifid ; the upper alternate, angled or lobed ; outer scales of the 

 involucre acuminate, hairy and viscid ; rays shorter thau the involucre. 

 Mountains of North Carolina. July - August. Stem 2 - 5 high. Heads 

 small, liays pale yellow. 



2. P. Uvedalia, L. Stem smooth, or rough-pubescent ; leaves broadlv 

 ovate, 3 - 5-lobed, coarsely toothed, rough above, pubescent beneath, abruptly 

 contracted into a sinuate-winged petiole ; outer scales of the involucre ciliate, 

 obtuse ; rays much longer thau the involucre. Rich soil. July - August. 

 Stem 3- 6 high. Rays bright yellow. 



35. ACANTHOSPERMUM, Schrank. 



Heads monoecious, radiate, many-flowered ; the rays pistillate, in a single 

 row; disk flowers stamiuate, tubular, 5-toothed. Involucre of 5 elliptical 

 scales. Receptacle flat. Acheuia compressed, armed on the back with rigid 

 hooked prickles, and enclosed in the outer scales of the chaffy receptacle. 

 Diffusely brandling herbs, with opposite leaves, and solitary heads of yellow 

 flowers. 



1. A. xanthioides, T)C. Prostrate, pubescent ; leaves petioled, oval or 

 obovate, toothed or entire ; chaff of the receptacle which encloses the ache- 

 nmm unarmed. Introduced in wool from South America several years ago, 

 and now a widely disseminated pest. 



2. A. humile, DC., with the chaff of the receptacle armed with 2 spines, 

 occurs as a ballast weed at Pensacola. 



36. CHRYSOGONUM, L. 



Heads many-flowered ; the rays 5, pistillate. Disk flowers tubular, 5-toothed, 

 sterile. Scales of the involucre in 2 rows; the exterior oblong, leafy ; the 

 interior roundish, clasping the oval compressed 4 angled fertile aehenia. 

 Receptacle flat, chaffy. Pappus a slightly lobed cup shaped crown, divided 

 on the inside to the base. A low hairy stokmiferous perennial herb, with 

 oval or spatulate-oblong opposite crenate leaves, and single heads of yellow 

 flowers borne on a long peduncle. 



1. c < Virginianum, L. Dry open woods, Florida to North Carolina. 

 Feb.- April. Plant at first simple, producing from a tuft of radical leaves 

 a single peduncled head, afterward stoloniferous and branching. 



37. SILPHIUM, T, 



Heads many-flowered ; the rays numerous, pistillate, fertile, in a single 

 TOW. Disk flowers cylindrical, sterile; the style undivided Scales of the 



