5. C. Virginiànus, Pursh. Stem woolly, slender, simple or sparingly branched (1--3° 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. mùticus, Pursh. (SWAMP THISTLE.) _Stem tall_ (3--8° 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. pùmilus, Torr. (PASTURE THISTLE.) _Stem low_ and stout (1--2° high), hairy, bearing 1--3 very large _heads_ (1½´ 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 diœcious, small and numerous._ C. ARVÉNSIS, Hoffm. (CANADA THISTLE.) Perennial, slender, 1--2° 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. CÁRDUUS, Tourn. PLUMELESS THISTLE. Bristles of the pappus naked (not plumose), merely rough or denticulate. Otherwise as in Cnicus. (The ancient Latin name.) C. NÙTANS, L. (MUSK THISTLE.) Biennial; leaves decurrent, sinuate, spiny; heads solitary, drooping; flowers purple.--Fields near Harrisburg, Pa., _Prof. Porter_. (Adv. from Eu.) 81. ONOPÓRDON, Vaill. COTTON or SCOTCH THISTLE. Receptacle deeply honeycombed, not setose. Pappus not plumose. Otherwise as Cnicus.--Coarse, branching annuals, or biennials, with the stems winged by the decurrent base of the lobed and toothed somewhat prickly leaves. Heads large; flowers purple. (The ancient Greek name of the plant.) O. ACÁNTHIUM, L. Stem (2--4° high) and leaves cotton-woolly; scales linear-awl-shaped.--Roadsides and waste places in the Atlantic States; rather rare. July--Sept. (Adv. from Eu.) 82. CENTAURÈA, L. STAR-THISTLE.