156 GAMOPETALOUS EXOGENS 



f f t Involucral scales att unarmed: heads small, imperfectly dioicous. 

 7. C. arvtnse, Scop. Rhizoma creeping; stem slender, paniculate at 

 summit; leaves simiate-pinnatifid, ciliate-spinose, undulate; heads 

 numerous, ovoid. 



Carduus arvensis. Sm. $ Fl. Cestr. ed. 2. p. 439. 

 FIELD CIRSIUM. Canada Thistle. 



JRhizoma perennial, creeping horizontally 6 or 8 inches below the surface of the 

 ground, and sending up erect biennial branches, or aerial stems, which are 18 inches 

 to 3 feet high. Leaves 4 to 8 or 10 inches long, slightly decurrent, the radical 

 (mes curled or wavy. Heads about half an inch in diameter, subpedunculate ; in- 

 volucral scales smoothish, minutely ciliate ; florets pale lilac-purple ; anthers whit- 

 ish, filaments nearly smooth. Akenes linear-oblong, slightly 4-cornered ; pappus 

 finally longer than the florets. 

 Bab. Fields, &c. Nat. of Europe. Fl. July. Fr. Aug. 



Obs. This foreigner (which, from the common name, seems to 

 have reached us by way of Canada,) is justly regarded as one of the 

 vilest vegetable pests that has yet invaded our country. It is, hap- 

 pily, yet rare in Chester County; and ought to be most vigilantly 

 watched, and promptly extirpated whenever it makes its appear- 

 ance. 



223. :LAP'PA, Tournef. 



[Gr. labein, to lay hold; from its hooked tenacious involucres.] 

 Heads many-flowered ; florets all similar and perfect. Involucre 

 globose; scales coriaceous, appressed at base, spreading and ab- 

 ruptly subulate above, with a rigid incurved point. Anthers with 

 bristly appendages or tips, and subulate tails at base. Style-branches 

 free and divergent. Akenes oblong, compressed, transversely 

 rugose ; pappus of numerous short rough deciduous bristles. Re- 

 ceptacle bristly. Biennials ? leaves alternate, petiolate, large ; heads 

 rather small ; florets purple, with bluish anthers. 



1, L. major, Gaertn. Lower leaves cordate-oblong, upper ones 

 ovate; involucre smoothish, or loosely cobwebby. 

 Arctium Lappa. L. # FL Cestr. ed. 2. p. 436. 

 GREATER LAPPA. Burdock. 



Stem 2 to 4 or 6 feet high, paniculately branching, roughish-pubescent. Leaves 

 green and roughish above, paler and cobwebby-tomentose beneath, radical ones 

 1 to 2 feet long, wavy and erosely dentate on the margin (sometimes pinnatifid, or 

 deeply and coarsely dentate) ; petioles 9 to 18 inches in length ; stem-leaves gradual- 

 ly smaller, and more or less ovate. Heads roundish-ovoid, % an inch to % in 

 diameter, on short peduncles, terminal and axillary. 

 Hal>. Waste places. Nat. of Europe. Fl. July. Fr. Sept. 



Obs. Every body, that has been in contact with its burs, knows 

 this coarse homely weed; but every body does not take care to keep 

 it in due subjection. The remarkable variety, with pinnatifid leaves, 

 is quite frequent about the streets of West Chester. 



SUBORDER II. LIGULAEFLO V RAE. 



Florets all ligulate and perfect, disposed in a radiatiform head. 



TRIBE 6. CICHORA^CEAE. 



Style-branches slender, rather obtuse, uniformly pubescent ; stigmatic lines term!- 



