1306 CARDUACEAE 



Heads not involucrate, but sometimes approximate to one or few leaves. 



Bracts of the involucre not spine-tipped, the outer ones often cuspidate. 1. C. muticus. 



Bracts of the involucre, at least the outer ones, spine-tipped. 

 Spines of the involucral bracts appressed or erect. 

 Body of the involucre 2 cm. thick or less. 



Leaf-margins densely spiny : glutinous line of the involucral bracts 



narrow. 2. C. repandus. 



Leaf-margins not densely spiny : glutinous line of the involucral bracts 



broad. 3. C. LeContci. 



Body of the involucre 3 cm. thick or more. 4. C. odoratus. 



Spines of the involucral bracts spreading. 



Inner bracts of the involucre narrow, with flattened soft tips. 

 Involucre less than 1.5 cm. thick. 



Leaf-blades merely spiny-toothed. 5. C. Virginianus. 



Leaf-blades pinnatifid or sinuate-pinnatifld. 



Tips of the outer involucral bracts 2 mm. long or more. 

 Leaves woolly on both sides. 



Leaf-blades thin, repand or repand-pinnatifid, with weakly 



spiny margins. 6. C. HeUeri. 



Leaf-blades thick, deeply pinnatifid, with rigidly spiny 



margins. 7. C. austrinus. 



Leaves glabrous above, tomentose or woolly beneath. 



Leaf-blades thick, revolute, with rigidly spiny margins. 8. C. revolutns. 



Leaf-blades thin, flat, with weakly spiny margins. 9. C. flaccidus. 



Tips of the outer involucral bracts 1 mm. long or less. 10. C. Nuttallii. 



Involucre over 1.5 cm. thick. 



Leaf-blades, except those near the heads, merely toothed. 11. C. altissimus. 



Leaf-blades 1-2-pinnatifid. 12. C. discolor. 



Inner bracts of the involucre, as well as the outer, spine-tipped. 13. C. lanceolatus. 



Heads involucrate, completely surrounded by a whorl of copiously spine-armed 



bracts. 



Bracts subtending the head much shorter than the inner involucral bracts. 14. C. pinetorum. 

 Bracts subtending the heads, at least the longer, surpassing the involucre. 15. C. spinosissimus. 



1. Carduus muticus (Michz.) Pers. Stem 1-2.5 m. tall, branching, ridged, lanu- 

 ginous or glabrate : leaves numerous ; blades oblong or oblong-ovate in outline, deeply 1-2- 

 pinnatifid, 2-4 dm. long or shorter on the upper part of the stem, glabrate above or 

 sparingly pubescent, thinly woolly-lanuginose beneath, all the divisions spine-tipped : 

 heads often numerous : involucres campanulate, woolly at the base ; bracts various, the 

 outer rather obtuse and cuspidate, the inner more elongated, with slender, slightly recurved 

 tips : disk purple : achenes 4-4.5 mm. long, shining : pappus-bristles plumose. 



In woods and thickets, Newfoundland to Saskatchewan, Florida and Texas. Summer and fall. 



2. Carduus repandus (Michx. ) Pers. Stem 1.5-5 dm. tall, simple or sparingly 

 branched, copiously leafy, more or less densely webby-lanate : leaves spreading ; blades 

 spatulate to narrowly oblong or broadly linear in outline, 5-12 cm. long, pinnately many 

 lobed, and copiously spiny along the edge, pubescent beneath like the stem, somewhat 

 floccose above : involucre 3-3.5 cm. high, the outer bracts 3-4 mm. wide, the tips of the 

 inner ones curled. 



In dry pine lands, North Carolina to Florida. Spring to fall. 



3. Carduus LeCdntei (T. & G.) Pollard. Stem 6-11 dm. tall, simple, more or less 

 floccose-woolly : leaves rather approximate, erect or ascending ; blades lanceolate in outline, 

 or those at the base of the stem oblanceolate, 8-12 cm. long on the lower part of the stem, 

 gradually reduced and generally very small and remote above, pinnatifid and with rela- 

 tively few spines on the margins : involucre 3.5-4 cm. high, the outer bracts 3-4 mm. wide, 

 the inner with erect tips. 



In low pine lands, Georgia and Florida to Louisiana. Spring to fall. 



4. Carduus odoratus Muhl. Stem 3-10 dm. tall, webby tomentulose, equally leafy, 

 sparingly, if at all branched : leaves usually quite numerous, the basal spreading ; blades 

 oblanceolate in outline, 1-2-pinnatifid, 1-2.5 dm. long, the divisions and teeth spine-tipped, 

 cauline leaves essentially similar to the basal but gradually smaller, partly clasping the 

 stem : heads solitary or few, conspicuous: involucre 3-4.5 cm. high, the outer bracts 4-5 

 mm. broad : achenes 4-4.5 mm. long. 



In fields and on hillsides, Maine to Pennsylvania and North Carolina. Summer. 



5. Carduus Virginianus L. Stem 0.5-1 mm. tall, often sparingly branched, some- 

 what arachnoid : leaves relatively few ; blades rather membranous, linear to linear- 

 oblong, or those of the lower cauline and basal leaves spatulate, 1-2.5 dm. long or shorter 

 above, acute, merely spinulose-toothed, otherwise entire, glabrous or nearly so above, closely 

 white pubescent or tomentose beneath : heads few, relatively small : involucres 10-15 mm. 

 high, slightly arachnoid, the outer bracts 1.5-2 mm. broad, tipped with slender rather 

 weak spines : achenes 3-3.5 mm. long. 



In open woods and thickets, Virginia and Kentucky to Florida and Alabama. Spring and summer. 



