Chapter C: LANCEOLATUS, Hoffm. (COMMON THISTLE.) Leaves decurrent on the stem,

forming prickly lobed wings, pinnatifid, rough and bristly above, woolly with deciduous webby hairs beneath, prickly; flowers purple. (Cirsium, _Scop._)--Pastures and roadsides, everywhere, at the North. (Nat. from Eu.)

[*][*] _Heads leafy-bracteate at base_ (see also n. 8); _proper scales not prickly._

1. C. horridulus, Pursh. (YELLOW THISTLE.) Stem stout (1--3 deg. high), webby-haired when young; leaves partly clasping, green, soon smooth, lanceolate, pinnatifid, the short toothed and cut lobes very spiny with yellowish prickles; heads (1--11/2' broad) surrounded by leaf-like and very prickly bracts, which usually equal the narrow scales; flowers pale yellow or purple. (Cirsium, _Michx._)--Sandy fields, Mass. to Va., and southward, near the coast.

[*][*][*] _Scales appressed, the inner not at all prickly._

[+] _Leaves white-woolly beneath, and sometimes also above; outer scales successively shorter, and tipped with short prickles._

2. C. Pitcheri, Torr. _White-woolly throughout_, low; stem very leafy; _leaves all pinnately parted into rigid narrowly linear and elongated, sometimes again pinnatifid divisions_, with revolute margins; flowers cream-color. (Cirsium, _Torr. & Gray_.)--Sandy shores of Lakes Michigan, Huron, and Superior.

3. C. undulatus, Gray. _White-woolly throughout_, low and stout, leafy; _leaves lanceolate-oblong_, partly clasping, undivided, _undulate-pinnatifid_, or rarely pinnately parted, moderately prickly; flowers reddish-purple. (Cirsium, _Spreng._)--Islands of L. Huron to Minn., Kan., and westward. The heads vary much in size.

4. C. altissimus, Willd. Stem downy, branching (3--10 deg. high), _leafy quite to the heads; leaves_ roughish-hairy above, whitened with close wool beneath, _oblong-ovate to narrowly lanceolate, undivided, sinuate-toothed, undulate-pinnatifid, or twice pinnatifid_, the lobes or teeth weakly prickly; heads 11/2--2' high; flowers chiefly purple. (Cirsium, _Spreng._)--Fields and copses, Mass. to Minn., and southward.

Var. discolor, Gray. Stem 2--6 deg. high; leaves nearly all deeply pinnatifid into lanceolate or linear lobes. (Cirsium discolor, _Spreng._)--Common; N. Eng. to Ill., and southward.

5. C. Virginianus, Pursh. Stem woolly, slender, simple or sparingly branched (1--3 deg. high), the _branches or long peduncles naked; leaves lanceolate_, green above, whitened with close wool beneath, ciliate with prickly bristles, _entire or sparingly sinuate-lobed_, sometimes the lower deeply sinuate-pinnatifid; heads small; outer scales scarcely prickly; flowers purple. (Cirsium, _Michx._)--Woods and plains, Va., Ohio, and southward.

[+][+] _Leaves green both sides, or only with loose cobwebby hairs underneath; heads large; scales scarcely prickly-pointed._

6. C. muticus, Pursh. (SWAMP THISTLE.) _Stem tall_ (3--8 deg. high), angled, smoothish, panicled at the summit; branches sparingly leafy, bearing single or few rather large _heads; leaves_ somewhat hairy above, whitened _with loose webby hairs beneath_ when young, _deeply pinnatifid, the divisions lanceolate_, acute, cut-lobed, prickly-pointed; _scales of the webby and glutinous_ (sometimes glabrate) _involucre_ closely appressed, _pointless_ or barely mucronate; flowers purple. (Cirsium, _Michx._)--Swamps and low woods; common.

7. C. pumilus, Torr. (PASTURE THISTLE.) _Stem low_ and stout (1--2 deg. high), hairy, bearing 1--3 very large _heads_ (11/2' broad), which are often _leafy-bracted_ at the base; _leaves green_, lanceolate-oblong, partly clasping, _somewhat hairy, pinnatifid, with short and cut very prickly-margined lobes; outer scales prickly-pointed_, the inner very slender; flowers purple or rarely white (fragrant, 2' long). (Cirsium, _Spreng._)--Dry fields, Maine to Penn., near the coast.

[*][*][*][*] _Outer scales of the appressed involucre barely prickly-pointed; heads imperfectly dioecious, small and numerous._

C. ARVENSIS, Hoffm. (CANADA THISTLE.) Perennial, slender, 1--2 deg. high, the roots extensively creeping; leaves oblong or lanceolate, smooth, or slightly woolly beneath, sinuate-pinnatifid, prickly-margined; flowers rose-purple. (Cirsium, _Scop._)--Cultivated fields, pastures, and roadsides, common; a most troublesome weed, extremely difficult to eradicate. (Nat. from Eu.)

80. CARDUUS, Tourn. PLUMELESS THISTLE.

Bristles of the pappus naked (not plumose), merely rough or denticulate. Otherwise as in Cnicus. (The ancient Latin name.)