74 COMPOSITAE 



* * Receptacle naked, sometimes hairy. 

 Chrysanthemum. Heads large, many- rayed; pappus none. 



Tanacetum. Heads small, corymbed, ray less; flowers yellow; pappus a short crown. 

 Artemisia. Heads small, racemose, spicate or panicled, rayless; pappus none. 

 Tribe Senecioneae. Heads radiate or discoid; involucral scales little if 

 any imbricated, not scarious; receptacle naked; pappus of soft capillary 

 bristles. 



Senecio. Flowers yellow ; heads usually radiate 



Cacalia. Flowers white or cream-colored, all perfect; heads discoid; sap often milky. 

 Erechtites. Flowers whitish, the marginal pistillate, the central perfect; heads dis- 

 coid. 

 Tribe Cynareae. Heads large, discoid; flowers tubular, perfect; involu- 

 cral scales much imbricated; anthers long-tailed at the base, elongated-ap- 

 pendaged at the tip; style-branches short or united, smooth, often with a 

 pubescent ring below. 



Arctium. Leaves not prickly ; involucral scales hooked; pappus of rough bristles. 

 Cnicls. Leaves prickly ; pappus-bristles plumose. 



VERNONIA Sehreb. Iron-weed. Perennials, with leafy stems, and corym- 

 bose cymes. Leaves alternate, acuminate Heads discoid, 15-40-flowered: 

 flowers purple, tubular, perfect. Involucre shorter than the flowers, of many 

 imbricated scales, the inner longest. Pappus double, outer scale-like, inner 

 copious, capillary. Receptacle naked. Achenes cylindrical, ribbed. Species 

 are with difficulty determined. 



V. fasciculata Mx. Stem 3-7 feet high, glabrous; leaves narrowly lanceo- 

 late to linear, sharply denticulate; heads many, cyme close, involucre bell- 

 shaped, half as long as the showy flowers; scales obtuse, closely appressed. 

 Low grounds; August-September; common. 



V. noveboracensis (L.) Willd. Stem 3-6 feet high, pubescent or glabrate, 

 leaves lanceolate, serrulate; iuvolucre purplish, scales ovate or lance-ovate, 

 with filiform or subulate spreading tips. Moist soil; July-September; re- 

 ported from Scott, Union, Pottawattamie, and Harrison counties. Specimens 

 from Des Moines, Lee, and Cass counties referred to this species. 



V. glauco (L.) Britton. Stem 2-5 feet high, glabrous, or finely pubescent; 

 leaves thin, the lower oval or obovate, the upper ovate-lanoeolate, acute or 

 acuminate, pale beneath, sharply serrate; inflorescence loosely branched; 

 heads few, slender-peduncled, 10-20-flowered; involucral scales acute or acu- 

 minate, appressed. Woods, August-September; reported, but questionable. 

 (V. noveboracensis Intlfolla Gray.) 



V. baldwinii Torr. Stout, 2-5 feet high, densely tomentose-pubescent; 

 leaves lanceolate or oblong-lanceolate, acute or acuminate, sharply serrate, 

 scabrous above, tomentulose beneath; heads stout-peduneled; involucral 

 scales acute or acuminate, squarrose. Dry soil; July-September. Forms 

 from Van Buren, Appanoose, Decatur, and Ringgold counties referred to this 

 species. 



EUPATORlUM L. Perennials. Flowers in corymbose heads, white, blue, 

 or red, never yellow, all tubular, 5-cleft. Involucre imbricate. Receptacle 

 flat, naked. Pappus a single row of capillary scabrous bristles. Style ex- 

 serted, deeply cleft. Achenes 5-angled. 



E. purpureum L. Jue-Pye Weed. Stem simple, 3-8 feet high, often pur- 

 plish, pubescent above, mostly glabrous below; leaves 3-8 in a whorl, short- 

 petioled, large, ovate-lanceolate to lanceolate, coarsely serrate, pointed; flow- 

 ers flesh-color; involucral scales numerous, imbricated ia several rows. Low 

 gounds; August-September; common. 



