COMPOSITAE. IO33 



l° n g< 3-5 cm - wide, pinnatifid into triangular acute dentate prickly lobes; basal 

 leaves petioled; heads solitary, terminal, 5-7 cm. broad, about 5 cm. high, often 

 involucrate by the upper leaves; outer bracts lanceolate or ovate lanceolate, with a 

 slight glutinous strip on the back, glabrous or sparingly tomentose, tipped with 

 slender prickles, the inner narrow, long-acuminate; flowers purple, rarely white, 

 fragrant In fields. Me. to Penn. and Del. July-Sept. 



12. Carduus Hillii (Canby) Porter. Hill's Thistle. (I. F. f. 4068.) Bien- 

 nial (?). low, villous-pubescent or somewhat woolly; stem leafy, simple or branched, 

 3-6 dm. high. Root perpendicular, fusiform, slender and hollow above, enlarged 

 below, 2.3 dm. long; leaf- lobes dentate, spinulose or with some rather stout prickles, 

 upper leaves oblong, sessile and clasping, the lower spatulate-oblong, narrowed at 

 the base or the lower petioled and 5 cm. long; heads 1.5-2 dm. broad, 5-7 cm. 

 high ; outer bracts of the involucre ovate-lanceolate, tipped with short bristles, 

 the inner narrowly lanceolate, long-acuminate; flowers purple. In fields, western 

 Out. to Minn., south to Penn., 111. and Iowa. June-July. 



13. Carduus spinosissimus Walt. Yellow Thistle. (I. P. f. 4069.) Bien- 

 nial or perennial, somewhat woolly when young, but becoming glabrate; stem 

 branched, leafy, 6-10 dm. high. Leaves green both sides, lanceolate or oblong in 

 outline, sessile and clasping or the basal ones short-petioled and somewhat spatu- 

 late, pinnatifid into triangular or broader spinulose-margined and prickle-tipped, 

 entire or dentate lobes; heads 5-10 cm. broad, 4-6 cm. high; bracts of the invo- 

 lucre narrowly lanceolate, roughish and ciliate. long-acuminate; flowers yellowish, 

 or occasionally purple. In moist or dry sandy soil, Me. to Penn., Fla. and Tex. 

 May-Aug., or earlier in the South. 



14. Carduus muticus (Michx.) Pers. Swamp Thistle. (I. F. f. 4070.) 

 Biennial; stem woolly or villous when young, becoming glabrate, slender, striate, 

 leafy, paniculately branched above, 1-2.5 m. high. Leaves densely white-tomen- 

 tose beneath when young, sometimes becoming glabrous on both sides, deeply pin- 

 natifid into lanceolate or oblong, entire, lobed or dentate, spiny segments usually 

 tipped with slender prickles; basal leaves petioled, 1-2 dm. long, those of the stem 

 sessile and smaller; heads about 4 cm. broad and high; outer bracts viscid, ap- 

 pressed, more or less cottony, ovate or ovate-lanceolate, the inner linear- lanceolate, 

 acute, all unarmed. In swamps and moist soil, Newf. to Fla., N. W. Terr, and 

 Tex. July-Oct. 



Carduus muticus subpinnatifidus Britton. Leaves lobed, not deeply pinnatifid, 

 green, and nearly glabrous on both sides. N. J. to W. Va. 



15. Carduus arvensis (L.) Robs. Canada Thistle. Creeping Thistle. 

 (I. F. f. 4071.) Perennial by horizontal rootstocks, forming patches, nearly gla- 

 brous; stems striate, 3-10 dm. high, branched above. Leaves sessile and slightly 

 clasping, lanceolate or oblong-lanceolate deeply pinnatifid into very prickly, lobed 

 or dentate segments; basal leaves sometimes petioled, 12-20 cm. long; heads nu- 

 merous, corymbose, purple or white; staminate heads globose, corollas projecting; 

 pistillate heads oblong-campanulate, corollas shorter, the long pappus conspicuous; 

 outer bracts ovate or ovate-lanceolate, appressed, tipped with short prickly points; 

 inner bracts of the pistillate heads linear, elongated. In fields and waste places, 

 Newf. to Va., S. Dak., Mont, and Kans. In many places a pernicious weed. 

 Nat. from Europe. June-Sep. 



16. Carduus nutans L. Musk Thistle. Plumeless Thistle. (I. F. 

 f. 4072.) Biennial, branched, sparingly tomentose, 6-9 dm. high. Leaves lanceo- 

 late in outline, deeply pinnatifid, acuminate, 7-15 dm. long, the lobes triangular, 

 very prickly; heads long-peduncled, 4-6cm. broad, purple, rarely white, fragrant; 

 bracts of the involucre in many series, long-acuminate, the prominent midnerve 

 prolonged into a prickle, or the inner nerveless and awned; pappus-bristles 20-25 

 mm. long. In waste places, Penn. and N. J. to N. B., and in ballast about the 

 seaports. Nat. or adventive from Europe. Native also of Asia. July-Oct. 



17. Carduus crispus L. Curled Thistle. Welted Thistle. (I. F. 

 f. 4073.) Biennial, somewhat tomentose; stem much branched, densely prickly. 

 6-12 dm. high. Leaves lanceolate in outline, with undulate and ciliate-spiny mar- 

 gins, all sinuate-pinnatifid into broad. 3 lol>ed. toothed segments, the teeth prickle- 

 pointed; heads several, usually crowded at the ends of the winged branches, 25 mm. 



