382 COMPOSIT4 CARDUUS 
oblong, more or less compressed, attached by their very base. 
Pappus of copious and rather rigid, long and plumous bristles in 
a single series, connected at the very base into a ring, so that they 
remain united after detaching. 
§ Perennials with camparatively small divecious heads. 
C. arvensis Robs. Brit. F]. 163. (Canapa Tuistie.) Stems 1-3 feet 
high from creeping perenhial rootstocks, corymbosely branching, usually 
glabrate and green: leaves lanceolate, pinnatifid and toothed, furnished 
with abundant weak prickles: heads loosely cymose, less than an inch 
high, dicecious, in staminate plants ovate-globular with the flowers well 
exserted; the pistillate oblong-campanulate, the flowers less exserted: 
bracts of the involucre appressed, short, with very small weak prickly 
points. A troublsome weed introduced from Europe: becoming too com- 
mon in the Willamette Valley 
§ 2 Biennials with the flowers all perfect. 
* Bracts of the involucre more or less unequal, all but the innermost — 
terminating in subulate, spinose spreading appendages. 
C. LANceoLatus L. Sp. 821. (Common TuisttE) Stems stout, 2-4 feet 
high, much branched: more or less vyillous-hirsute: leaves lanceolate, 
deeply pinnatifid w'th lanceolate lobes, rigidly prickly, upper face strigose- 
setulose; the base decurrent on the stem into interrupted prickly wings: 
heads obovoid, 1-2 inches high, terminating the stems and branches: 
bracts of the involucre arachnoid-woolly, lanceolate and mostly attenua‘e 
into slender spreading spines: corollas rose-purple. Pastures and waste 
places throughout the northern United States. Naturalized from Europe. 
* * Bracts of-the ovoid or hemispherical involucre ar ae 
cate, the outer succcessively shorter, all with loose and dilated fimbri- 
ate or lacerate white-scarious tips. 
C. Americanus Greene Proc. Phila?. Acad. Stems rather slender, 2-4 
feet high, branching above, the branches bearing tg or scattered 
naked heads leaves white-tomentose beneath, lanceolate or broader, sin- 
uately pinnatifid or some nearly dentate, others pinnately parted, weakly 
prickly: heads erect. one inch high; principal bracts of the involucre 
naked-edged or merely fimbriate-ciliate below, and the dilated scarious 
apex as broad as long, fimbriate-lacerate, tipped with barely exserted cusp 
or mucro; innermost with lanceolate nearly entire scarious tips: flowers 
ochroleucous: stronger pappus-bristles dilated-clavellate at tip. Willam- 
ette Valley Oregon to Colorado and New Mexico. 
* * * Bracts of the involucre mostly loose, not appressed-im bricate 
nor rigid, tapering gradually from a narrow base toa slender prickly 
muticose apex ; outer not very much shorter than the inner, wholly 
destitute of dorsal glandular ridge or spot. 
+ Some bracts of the involucre with scarious or fringed tip or mar- 
gins,tat least the innermost slightly or not at all prickly-pointed: 
leaves.,not decurrent on the stem, moderately prickly. 
C. remotifolius Hook. FI. i, 302. Loosely arachnoid-woolly when 
young: stems 2-8 feet high: leaves from sinuately to deeply pinnatifid, 
more or less whitened by the loose tomentum beneath even in age: heads 
12-18 lines high, pedunculate, scattered, naked or nearly so at base: invo- 
lucre lightly arachnoid and glabrate; the bracts attenua'e, the outer into 
a weak small prickle; the inner or some of them with a scarious entire or 
sparingly lacerate tip: corollas ochroleucous, their lobes much shorter than 
the throat: pappus of coarse bristles, the strongest with conspicuously 
