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 em. thick or iess. 
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. LeContet. 
Body of the involucre 3 em. 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 braets 2 mm. long or more. 
Leaves woolly on both sides. 
Leaf-blades thin, repand or repand-pinnatifid, with weakly i 
spiny margins. i 6. C. Helleri. 
Leaf-blades thick, deeply pinnatifid, with rigidly spiny f 
margins. 7. C. austrinus. 
Leaves glabrous above, tomentose or woolly beneath. i 
9 
Leaf-blades thick, revolute, with rigidly spiny margins. . C. revolutus. 
Leaf-blades thin, flat, with weakly spiny margins. . C. flaccidus. 
Tips of the outer involucral bracts 1 mm. long or less. 10. C. Nuttallii. 
Involucre over 1.5 em. thick. ae 
Leaf-blades, except those near the heads, merely toothed. 1l. C. altissimus. 
Leaf-blades 1-2-pinnatifid. 12. C. discolor. 
Inner bracts of the involucre, as well as the outer, spine-tipped. 18. C. lanceolatus. 
Hor involucrate, completely surrounded by a whorl of copiously spine-armed 
racts. 
Bracts subtending the head much shorter than the inner involucral bracts. 14. C. pinetorum. 
Braets subtending the heads, at least the longer, surpassing the involucre. 15. C. spínosissimus. 
1. Carduus miticus (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 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 repándus (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 Le Cóntei (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 odoràtus Muhl. Stem 3-10 dm. tall, webby tomentulose, equally leafy, 
A vadit if at all branched : leaves usually quite numerous, the basal spreading ; eere 
oblanceolate in outline, 1-2-pinnatifid, 1-2.5 dm. long, the divisions and teeth Ape E 
cauline leaves essentially similar to the basal but gradually smaller, partly clasping cs 
stem : heads solitary or few, conspicuous: involucre 3-4.5 cm. high, the outer bracts 
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 morn 
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 ns 
high, slightly arachnoid, the outer bracts 1.5-2 mm. broad, tipped with slender rathe 
weak spines: achenes 3-3.5 mm. long. 
In open woods and thickets, Virginia and Kentucky to Florida and Alabama. Spring and summer. 
