398 composite. 



heads ; the flowers red, purple, or rose-color, rarely white or yellowish, in summer. 

 Many hybridize ! — L. Gen. ed. 6, 409 (where the char, is pappus plumosus, and 

 in Spec. ed. 2, two years earlier, C. benedictus is referred to Gentaurea) ; Willd. 

 Spec. iii. 1662; Benth. & Hook. Gen. ii. 468. Cirsium, DC. Fl. Fr. ed. 3, iv. 

 110, & Prodr. vi. 634, not Tourn. 



§ 1. Naturalized from Europe : one species with dioecious heads. 



C. arvensis, Hoffm. (Canada Thistle). Perennial and spreading by creeping root- 

 stocks, a foot or two high, corymbosely branching, usually glabrate and green : stem and 

 branches wingless : leaves lanceolate, pinnatifid and toothed, furnished with abundant weak 

 prickles ■ heads loosely cymose,\less than inch high, dioecious; in male plant ovate-globular, 

 and flowers (rose-purple) well exserted ; in female oblong-campanulate and flowers less pro- 

 jecting : bracts of involucre all appressed, short, and with very small weak prickly points : 

 only abortive anthers to the female flowers. — Fl. Germ. iv. 180 ; Pursh, Fl. ii. 506. Serratula 

 arvensis, L. Spec. ii. 820; Fl. Dan. t. 644. Carduus arvensis, Curt. Fl. Lond. t. 57; Engl. 

 Bot. t.~975. Cirsium arvense, Scop. Fl. Cam. ; DC. Prodr. vi. 643; Torr. Fl. N. Y. i. 408, 

 t. 61 ; Eeichenb. Ic. Fl. Germ. t. 842. Breea arvensis, Less. Syn. 9. — Meadows, pastures, 

 and waste grounds, from Newfoundland through the Northern and Middle Atlantic States : 

 too common weed. (Nat. from Eu.) 



C. lanceolatus, Hoffm. 1. c. (Common Thistle of fields.) Biennial, 3 or 4 feet high, with 

 large heads (almost 2 inches high) terminating somewhat leafy branchlets, cottony-tomen- 

 tose when young, becoming green, more or less villous or hirsute : leaves lanceolate, deeply 

 pinnatifid and with lanceolate lobes, rigidly prickly; upper face strigose-setulose ; base 

 decurrent on the stem into interrupted prickly wings : bracts of involucre arachnoid-woolly, 

 lanceolate and mostly attenuate into slender and rigid prickly-pointed spreading tips : flow- 

 ers rose-purple, hermaphrodite. — Willd. Spec. iii. 1666 ; Pursh, 1. c. Carduus lanceolatus, L. ; 

 Engl. Bot. t. 107; Fl. Dan. t 1173. Cirsium lanceolatum. Scop. 1. c. ; DC. 1. c. ; Eeichenb. 

 Ic. Fl. Germ. t. 826. — Pastures and waste grounds, Newfoundland and Canada to Georgia 

 (very common northward) ; also in Oregon. (Nat. from Eu.) 



§ 2. Indigenous species, all but one Alaskan species endemic, all or mostly 

 biennials. 



* Bracts of the ovoid or hemispherical involucre appressed-imbricated and the outer successively 

 shorter, all with loose and dilated fimbriate or lacerate white-scarious tips. — Eckenais, 

 Cass., DC. 



C. Americanus, Gray. A foot or two high, branching above : branches bearing solitary 

 or scattered naked heads : leaves white-tomentose beneath, lanceolate or broader, sinuately 

 pinnatifid , or some merely dentate, others pinnately parted, weakly prickly : heads erect, inch 

 high ; principal bracts of the involucre naked-edged or merely fimbriate-ciliate (not setose- 

 spinuliferous) below, and the dilated scarious apex as broad as long, fimbriate-lacerate, 

 tipped with barely exserted cusp or mucro ; innermost with lanceolate nearly entire scarious 

 tips: flowers ochroleucous : stronger pappus-bristles dilated-clavellate at tip. — Proc. Am. 

 Acad. xix. 56, without char. C. carlinoides, var. Americanus, Gray, Proc. Am. Acad. x. 48, 

 & Bot. Calif, i. 420, excl. syn. Nutt., &c. Echenais carlinoides, var. nutans, Gray, Proc. Acad. 

 Philad. 1863, 69. — Lower mountains of Colorado and New Mexico to the coast of California. 

 ( A hybrid with C. undulatus ? with red-purple flowers and purplish tips to involucral bracts, 

 is from Pinos Altos Mountains, New Mexico, Greene. ) 



* # Bracts of the involucre mostly loose, not appressed-imbricated nor rigid, tapering gradually 

 from a narrow base to a slender-prickly or muticous apex; outer not very much shorter than 

 the inner, wholly destitute of dorsal glandular ridge or spot, 



-f— Some with scarious or fringed tip or margins, at least the innermost, slightly or not at all 



prickly-pointed (except accessory leafy ones): leaves not decurrent on the stem, moderately 



prickly : Rocky Mountain and Western species. 



C. Parryi, Gkat. Green, lightly arachnoid and villous when young, 2 feet or so high : leaves 



lanceolate, sinuate-dentate : heads (inch high) several and spicately glomerate or more race- 



mosely paniculate, more or less bracteose-leafy at base : accessory and outer proper bracts 



or some of them pectinately fimbriate-ciliate down the sides, innermost with more or less 



