1306 CAEDUACEAE 



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. muticuf. 



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. LeContn. 



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-pinnatifid. 



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. Helkri. 



Leaf-blades thick, deeply pinnatifid, with rigidly spiny 



margins. 7. C. austriniis. 



Leaves glabrous above, tomentose or woolly beneath. 



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



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. $pinosissimus. 



1. Carduus muticus (Michx. ) 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 wooUy-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 plumo.se. 



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 

 wliite 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. 



