CARDUACEAE 1481. 
124. CIRSIUM Filion Hil. Annual, biennial or perennial, large 
or coarse herbs. Leaves alternate: blades toothed, lobed, or pinnatifid, usually 
spiny. Heads erect, often showy. Involucre with the outer bracts, at least, 
eae tipped or spiny margined. Flowers violet, purple, lilac, or yellowish, or 
white. “Filan no mostly pubescent. Pappus of elongate capillary, 
cl bristles in several series.—More than 200 species, iniu distributed 
in the Northern D —Sum.fall or all year S.—THISTLES. BULL 
THISTLES. 
Heads not involucrate, but sometimes approximate to 1 or few bract-like leaves. 
Bracts of the involucre not spine-tipped. 
Heads solitary or few, large, the involucre over 2 cm. 
in diameter. I. MUTICA. 
x n small, the involucre less than 2 em. 
n diam II. ARVENSIA. 
Bad: “of the ene at least the outer spine-tipped. 
Spines of the involucral bracts appressed or erect. III. REPANDA. 
Sp. of the involucral bracts spreading. 
ner bracts of the involucre narrow, with soft 
“dattened tips. IV. ALTISSIMA. 
Inner bracts of the involucre, as well as outer spine- 
ippe V. LANCEOLATA. 
m jnvolucrate, surrounded by a whorl of spinescent 
VI. HORRIDULA. 
I. Mu 
Rather tall plant with woolly involucral pam and deeply 
pinnatifid leaf-blades. 1. C. muticum. 
! II. ARVE 
Very spiny erect or diffuse plant T pue of numerous 
small, lilac-colored, heads of flow 2. C. arvense. 
III. REPANDA 
Body of the involucre 2 cm. thick or less 
Leaf-margins Eel y Spiny: glutinous line of the involu- 
eral bracts n 3. C. repandum. 
Leaf-margins nor "de oseio spiny: glutinous line of the in- 
volueral bracts broad. 4. C. LeContei. 
Body of the involucre 3 cm. thick or more. 5. C. odoratum. 
IV. ALTISSIMA 
Involuere less than 1.5 cm. thick. 
Le i? 2 Bees apio lanate-tomentose beneath. 
lades merely spiny toothed: spines of the involu- 
x DR slender, over 2 mm. lon 6. C. virginianum. 
Leaf-blades pinnatifid: or sin nuate- pinnatifid : Bel ee of 
e involucral bracts stout, less than 2 mm. long. T. C. revolutum. 
Leaf-blades thinly lanate-tomentose beneath. 
eaf-blades with weak, rather few, marginal spines: 
pores of the involücral bracts over 2 mm. lon 8. C. flaccidum. 
a with long and stout, very numerous mar- 
nal E spines of the involucral braets less than 
2n . lon 9. C. Nuttallii. 
Involucre ov er l 
WX ene thick. 
Leaf-blades, exe cept those near the heads, merely toothed. 10. C. altissimum. 
Leaf-blades 1-2- -pinnatifid. 11. C. discolor. 
V. LANCEOLAT 
Very spiny plant with decurrent leaves: m e flowers bril- 
liant-violet. 12. C. lanceolatum. 
VI. HORRIDULA 
Involueral bracts all serrulate-ciliate 
twice as long as the filaments. 9. C. vittatum. 
Basal leaves with broad pinnatifid blades: anthers about l 
as long as the filaments. 14. C. Smallii. 
Involucral bracts puberulent or pubescent, but not ciliate. 15. C. horridulum. 
1. C. m Miehx. Stem 8-25 dm. tall, angled, sors id or glabrate: 
leaf blades aa to elliptic-ovate, 1—2-pinnatifid, mainly 17-40 em. long, 
