COMPOSITAE. 1033 



long, 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 

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



13. Carduus spinosissimus Walt. YELLOW THISTLE. (I. F. f. 4069.) Bien- 

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

 branched, leafy, 6-iodm. 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. 5m. 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 miiticus 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. 



1 6. 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 ttridnerve 

 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 lobed, toothed segments, the teeth prickle- 

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



