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SYXGEXESIA 439 



6. C. auvkvsts, Sm. Stem paniculate ; leaves sessile, lanceolate, 

 pinnatifid and dentate, spinose, undulate, smoothish ; involucre ovoid, 

 small, the leaflets lance-ovate, mucronate, appressed. Beck, Hot. p. 



172. 



Serratula arvensis. Willd. Sp. 3. p. 1646. Alt. Kew. 4. p. 473. 



Cnicus arvensis. Atuhl. Catal. p. 70. Puvsh, Am. 2. p. 506, BigeU 



Bost. p. 291. Tow. Com/), p. 281. Eat. Man. p. 100. 



Breca arvensis, J,ess. Sy?i.p. 9. 



Field Cahduus. Vulgd — Canada Thistle. 



Gallice — Chardon aux anes. Gevinanice — Die Ackerdistel. 



Root perennial, creeping, anil exceedingly tenacious of life. Stem 18 inches to 

 3 feet huh, erect, slender, striate, smoothish, paniculately branched, branches 

 slender, lanuginous. leaves sessile, slightly decurrent, smoothish, sometimes 

 lanuginous beneath. Heads numerous, terminal, sub-pedunculate, ovoid, small 

 (I third to 2 thirds of an inch in diameter); leaflets of the involucre appressed, 

 lance-ovate, mucronate* with the point a little spreading, smoothish, minutely cil- 

 iate. Florete purple (rarely whitish), mostly perfect ? (dioicous, Lessing). Akenes 

 linear-oblong, slightly 4-cornered ; pajtpus finally longer than the florets. 



Hub. Great Valley; Kimberton: rare. Fl. July. Fr. August. 



Obs. This foreigner,— the vilest pest that ever invaded the farms of our coun- 

 try, in the form of a weed,— was first observed in the Great Valley, near the War- 

 ren Tavern, in 18*26, by Mr. Joshua Hoopes ;— and has been found, since, at Kim- 

 berton, and in one or two other localities. It appears to have been introduced 

 among Timothy seed. The utmost vigilance will be required, to prevent it from 

 spreading. It was a singular taste, in Lessing, to dedicate so hateful a plant to a 

 rospectable Botanist. 



# » 



Radical leaves only pinnatifid. 



7. C. altjssimus, L. Stem-leaves sessile, oblong-lanceolate, dentate 

 and somewhat spincsccnt-ciliate, roughish above, tomentose beneath, 

 radical ones petiolate, pinnatifid ; involucre oblong-ovoid, bractcate at 

 base ; leaflets of the involucre ovate-lanceolate, appressed, with a spread- 

 ing spine at apex, Beck, Hot. p. 1 72. 



Cnicus altissimus. JVilld. and most of the Authors here quoted. 

 Tallest Carduus. 



Root perennial ? Stem 3 to 6 or 8 feet high, erect, branching and slender above 

 sulcate-striate, roughish-pubescent. Leaves hoary-tome ntose beneath, the radical 

 ones large (12 to 18 inches long, and 3 to 5 or 6 inches wide), pinnatifid, petiolate, 

 the cauline ones sessile, dentate or denticulate, ciliate with slender spines, or 

 spinesccnt bristles. Heath oblong-ovold, about an inch in diameter, with linear- 

 lanceolate spinescent-ciliate bracts at base ; leaflets of the involucre ovate- lance- 

 olate, appressed, slightly connected by a lanuginous web, of a livid color near the 

 apex, terminating in a subulate keeled spreading spine— the inner leaflets lance- 

 linear and scarcely spinose. Florets purple, often palish. 



Hab. Fencerows ; thickets, &c. frequent. Fl. August. Fr. September. 



Obs. This is usually taller than our other species of Carduus,— and is readilr 

 distinguished by its stem-leaves not being pinnatifid. One or two additional spe- 

 cies are enumerated in the U. States. 



