SPECIES AND VARIETIES. 267 



C. palustris: annual or biennial; stems stiff, scarcely 

 branched,, 4-5 feet high, quite covered with the prickly de- 

 current margins of the leaves ; leaves long, narrow, pinnatifid 

 with numerous ovate wavy prickly lobes, and a few rough hairs 

 scattered on both surfaces ; flower-heads numerous, small, 

 ovoid, usually collected in clusters, forming an irregular ter- 

 minal corymb ; involucral bracts numerous, with very small 

 somewhat prickly points, the inner ones often coloured ; florets 

 purple. Wet fields and meadows. Fl. July, August. 



ft Leaves sessile or very partially decurrent. 



C. arvensis : stems erect, 3-4 feet high ; leaves narrow, 

 pinnatifid, very prickly, either embracing the stem with prickly 

 auricles or shortly decurrent ; flower-heads in loose terminal 

 corymbs, dioecious ; the males nearly globular, with project- 

 ing purple florets, the females with much longer involucres 

 and shorter florets; involucral bracts numerous, appressed, 

 with small prickly points. Cultivated and waste places. Fl. 

 July. 



C. heterophyUus : stems stout, 34 feet high, deeply fur- 

 rowed, with a little loose cottony wool, not prickly ; leaves 

 clasping the stem, with scarcely decurrent auricles, lanceolate, 

 glabrous above, cottony white beneath, bordered with small, 

 bristly but scarcely prickly teeth, sometimes slightly lobed ; 

 flower-heads large, growing singly on long peduncles ; involu- 

 cral bracts glabrous, lanceolate, obtuse, or with a very minute 

 not prickly point. Mountain pastures. Fl. July, August. 



C. pratensis : stems 12 feet high, usually simple, with a 

 single ovoid flower-head, or occasionally divided into 23 long 

 one-headed branches; leaves sinuate or shortly pinnatifid, the 

 stem-leaves lanceolate, bordered with short, slightly prickly 

 teeth ; heads somewhat cottony ; involucral bracts lanceolate, 



