3(1). Heads solitary; mature achenes stipitate 42. Cotula, p. 1686 



3. Heads in spikes, racemes or panicles; achenes not noticeably stipitate 



43. Artemisia, p. 1689 



VUl. Key to Genera of Senecioneae 



1. Leaves opposite 44. Arnica, p. 1689 



1. Leaves alternate (2) 



2(1). Rays present 45. Senecio, p. 1689 



2. Rays in the usual sense absent (3) 



3(2). Marginal pistillate flowers present, their corollas filiform with slight funnel- 

 form throat and 3- to 5-lobed summit; annuals 



47. Erechtites, p. 1693 



3. Marginal pistillate flowers absent; perennials 46. Cacalia, p. 1693 



IX. Key to Genera of Cynareae 



Pappus bristles plumose, at least in the lower part 48. Cirsium, p. 1694 



X. Key to Genera of Cichorieae 



1. Achenes more or less strongly flattened; large coarse plants usually more than 

 4 dm. tall 49. Lactuca, p. 1698 



1. Achenes terete or prismatic, scarcely flattened; relatively small delicate plants 



rarely to 3 dm. tall (2) 



2(1). Achenes spinulose or with some short processes near the summit of the 

 body, tipped by a slender beak 51. Taraxacum, p. 1703 



2. Achenes smooth or nearly so, not evidently spinulose or muricate (3) 



3(2). Plants with at least a few cauline leaves, these sometimes much-reduced; 

 heads several or numerous to rarely solitary 50. Crepis, p. 1703 



3. Plants strictly soapose, with solitary heads 52. Agoseris, p. 1704 



1. Vernonia Schreb. Ironweed 



Perennial herbs; leaves alternate, pinnately veined, mostly narrow and willow- 

 like; heads in terminal corymbiform aggregation, usually 5-14 mm. broad; re- 

 ceptacle flat or convex, essentially naked; involucre usually campanulate-cylindric; 

 phyllaries in several series, strongly imbricated; ray flowers absent; disk flowers 

 numerous, perfect, fertile, the corolla mauve or purple or rose-colored, rarely 

 white but never yellow; anthers not caudate; style branches elongate, filiform- 

 subulate (not thickened upward), hispidulous throughout, with stigmatic lines 

 only near the base; achenes 6- to 10-ribbed, commonly resin-dotted between the 

 ribs; pappus fuscous-white or rusty-white, persistent, double, of numerous coarse 

 bristles. 



About 1,000 species in America, Africa, Asia and Australia. Our species show 

 considerable evidence of genetic intercontamination; the determination of some 

 specimens is thus difficult if not impossible. 



I. Phyllaries long-acuminate or prolonged into long filiform tips 



1. V. crinita. 



1. Phyllaries obtuse, acute or acuminate (2) 



2(1). Principal cauline leaves ovate to lanceolate, mostly hairy or tomentose 

 beneath (5) 



2. Principal cauline leaves linear-lanceolate to narrowly linear, mostly glabrous 



and pitted beneath (3) 



1592 



