disk flowers numerous, perfect, fertile; corolla equally 5-toothed, yellow; achenes 

 columnar, nearly terete, several-nerved, alike in ray and disk; pappus of numerous 

 capillary bristles. 



An enormous world-wide genus of between 2,000 and 3,000 species, reputed 

 to be among the several largest seed-plant genera. 



1. Woody, moderately branched shrub; old bark gray, new bark reddish, youngest 

 twigs green and finely striate; ray flowers 2 to 8, ligules about 6 

 mm. long, pale yellow; southern Arizona 7. S. salignus. 



1. Annual or perennial herbs (2) 



2(1). Annual; terminal lobes of leaves in lower half of stem usually 1-3 cm. 

 wide 1. S. glabellus. 



2. Perennial (3) 



3(2). Plants of eastern Oklahoma; phyllaries purple tipped; achenes glabrous.... 

 2. S. aureus. 



3. Plants of New Mexico (4) 



4(3). Cauline leaves well-developed, only gradually reduced upwards; no well- 

 developed tuft of basal leaves present (5) 



4. Cauline leaves generally strongly and progressively reduced; basal or lower 



cauline leaves well-developed (6) 



5(4). Cauline leaves (at least in part) sessile, with broad more or less clasping 

 base; phyllaries with a blackish tip 3. S. crassulus. 



5. Cauline leaves (except sometimes the reduced upper ones) petiolate or tapering 



to a narrow base, the lower leaves triangular with deltoid to cordate 

 base 4. S. triangularis. 



6(4). Basal leaves (or some of them) cordate or subcordate, sharply toothed; 



cauline leaves laciniate-pinnatifid at least toward their bases 



5. S. pseudaureus. 



6. Basal leaves not cordate nor subcordate but rather elliptic or oblanceolate, 



crenate or serrate to subentire 6. S. pauperculus. 



1. Senecio glabellus Poir. Butterweed. 



Annual 1-4 (-10) dm. tall; leaves pinnately lobed, lateral lobes oblong, undu- 

 late-margined, basally (toward the axis) not or only slightly constricted, the 

 terminal lobe irregularly undulate. 



Rare in sandy soil and moist or wet shady places in Okla. {Waterfall) and e. 

 Tex. (Gregg and San Augustine cos.), spring; s.e. U.S., n. to N.C., 111. and Mo., w. 

 to Kan., Okla. and Tex. 



2. Senecio aureus L. 



Perennial from a branched rhizomatous caudex or creeping rhizome, sometimes 

 with coarse and leafy offshoots; herbage lightly floccose-tomentose when young, 

 glabrescent; stem 2-12 dm. high; basal leaves long-petioled, cordate, suborbicular 

 to ovate, crenate or serrate; cauline leaves variously pinnatifid, usually reduced 

 and becoming sessile upward; heads few to many, with golden-yellow ligules 6-13 

 mm. long (rarely ray flowers absent), the disk 5-12 mm. wide; involucre 5-10 

 mm. high, the phyllaries often purple-tipped; achenes glabrous. 



Swamps and wet or moist woodlands in Okla. (Delaware Co.), Apr.-Aug.; Lab. 

 to Ga. and Ala., w. to Minn, and e. Okla. 



3. Senecio crassulus Gray. 



Perennial plant; stem 2-5 dm. high, rarely less, mostly leafy to the apex; leaves 

 8-15 cm. long, oblong-lanceolate to linear-oblanceolate or obovate, denticulate, 

 glabrous or essentially so, lower leaves cuneate to a winged petiole, the upper 

 sessile and partly clasping, sometimes strongly reduced; heads 10-15 mm. high, 



1690 



