Class XIX. Order I. 291 



308. CNICUS. 



CNICUS ARVI:NSIS. Willd. Canada Thistle. 



Leaves sessile, pinnatifid, spinous ; stem panicled ; 

 calyx ovate, its spines minute ; down feathery. Sm. 



Syn. CARDUUS ARYENSIS. Sm. 

 SERRATULA ARVENSIS. L. 



This species is easily distinguished from the rest of our this- 

 tles by its small flowers, and its thornless calyx scales. It com- 

 monly forms beds by its perennial, creeping 1 roots, and is exceed- 

 ingly difficult to extirpate. The stems are two or three feet 

 high, smooth, many flowered. Leaves alternate, sessile, pinnati- 

 fid, with numerous lobes, and very thorn}'. Flowers terminal, 

 purple ; the scales of the calyx ending in a short, weak bristle, 

 rather than a spine. This plant seems to have come to us from 

 the westward, where it is exceedingly troublesome. The name 

 of Cursed thistle has been given it in England. July. 



* CNICUS GLUTINOSUS. Glutinous Thistle. 



C.foliis pinnatifidis, laciniis divaricatis ; calyce ova- 

 to, squamis muticis, glutinosis. 



Leaves pinnatifid with divaricate segments ; calyx 

 ovate with unarmed glutinous scales. 



Stem from four to six feet high, branching, more or less downy. 

 Leaves sessile, somewhat clasping, more or less downy, pinnati- 

 fid ; the segments subdivided, divaricating, spinous. Flowers 

 small, deep purple, on slender stalks or branches. Calyx ovate ; 

 the scales appressed, glutinous on the back, of a brownish colour, 

 connected by a white web, so as to appear speckled, ending in a 

 short, softish point, which is longest in the uppermost. In damp, 

 rich soils. August, September. Biennial. 



It is one of the handsomest of the genus. Nearly allied to 

 Cirsium muticum of Michaux, but appears to differ in its leaves 

 and its ovule glutinous calyx. 



CNICUS HORRIDULUS. Yellow Thistle. 



Leaves sessile, pinnatifid, acutely cut, thorny ; in- 

 volucre many leaved, one flowered. 



