584 COMPOSITAE (COMPOSITE FAMILY) 



multicapitatus Greenm. ex Rydb. 1. c. 33: 160.) Nebraska and Colorado to 

 Texas and Arizona. 



40. Senecio spartioides T. & G. 1. c. 438. Glabrous throughout; stems 

 suffruticose, 2-4 dm. high, very numerous from the same ligneous taproot, 

 rigid, corymbose at the summit, leafy: leaves fleshy, narrowly linear, per- 

 fectly entire or sparingly pinnately parted, rather obtuse, sessile: heads (large 

 and showy) fastigiate-corymbose, on short minutely bracteolate peduncles: 

 the calyculate bracts subulate, minute; bracts of the cylindrical involucre 

 about 12, lanceolate-linear, acutish: rays mostly 7, oblong-linear, elongated: 

 achenes silky-canescent. This and the two preceding were included in the 

 Manual under S. Douglasii, a Californian species. Wyoming to Arizona and 

 Texas. 



41. Senecio vulgaris L. Sp. PI. 867. 1753. An erect annual, 1-3 dm. or 

 more high; herbage somewhat succulent, glabrous or with a little loose to- 

 mentum: leaves sessile, auricled, pinnatifid, the lobes oblong and with irregu- 

 larly dentate margin: heads in terminal cymose clusters; involucre 6 or 7 mm. 

 high; principal bracts about 20, their tips black and often penicillate; small 

 outer bracts several, black: achenes slightly pubescent. Occasionally found 

 in waste grounds; introduced from Europe; flowering the whole season through; 

 commonly called GROUNDSEL. 



91. CARDUUS L. THISTLE 



Stout herbs, mostly biennial. Leaves mostly sessile or decurrent, and with 

 sharply spinose lobes or teeth. Heads large, ovoid or subglobose; the pluri- 

 serial and imbricated involucral bracts usually prickly tipped. Receptacle 

 densely villous-setose. Flowers all alike, crimson, purple, or white, the seg- 

 ments of the cort>lla long and linear-filiform. Achenes obovate or oblong, 

 compressed, smooth, not striate. Pappus a single series of long and barbellate 

 or plumose slender bristles united at base and deciduous in a ring, often 

 clavellate-dilated at the naked tip. Cnicus. 



Dioecious; heads small; perennial by spreading rootstocks . . 1. C. arvensis. 

 Hermaphrodite; heads larger; biennials or rarely perennials. 



Bracts of the involucre (at least most of them) with notably di- 

 lated fringed tips. 

 Bracts conspicuously arachnoid-pubescent; foliage green and 



becoming glabrate . . . . . . . 2. C. Parryi. 



Bracts not arachnoid-pubescent or only slightly so on the 

 edges; foliage green above, more or less white-lanate be- 

 neath . . ... . . . . . 3. C. americanus. 



Bracts of the involucre (at least some 9f them) with spiny tips. 

 Bracts not with a glandular dorsal ridge. 



Bracts conspicuously arachnoid-pubescent . . . 4. C. Hookerianus. 



Bracts not arachnoid or only moderately so on the edges. 

 Inner bracts innocuous, long-attenuate. 



More or less dilated, crisped, twisted, or laciniate . 5. C. foliosus. 



Usually not at all dilated, crisped or twisted. 

 Erect or only the tips or spines squarrose. 



Stem simple, very strict (or wanting); heads soli- 

 tary, few, glomerate . . . . 6. C. Drummondii. 



Stem more or less branched; heads less crowded . 7. C. bipinnatus. 

 Bracts squarrose or the lower even reflexed . 8. C. neo-mexicanus. 



Inner bracts also spine-tipped . . . . . . 9. C. lanceolatus. 



Bracts with a glandular dorsal ridge. 

 Flowers ochroleucous. 



Spine of involucral bracts short, flat, widely spreading . 10. C. Nelsonii. 

 Spine of involucral bracts long, not flattened, mostly 



erect 11. C. plattensis. 



K lowers rose or purple. 



Leaves permanently tomentose on both sides. 



Involucres usually less than 4 cm. broad . . .12. C. undulatus. 

 Involucres usually 4-6 cm. broad. 



Spines half as long as the bracts . . . . 13. C. megacephalus. 



Spines as long as the bracts 14. C. ochrocentrus. 



Leaves becoming green and glabrate on the upper side . 15. C. filipendulus. 



1. Carduus arvensis (L.) Robs. Brit. Fl. 163. 1777. Stems 3-8 dm. high, 

 from creeping perennial rootstocks, corymbosely branching, usually glabrate 



