COMPOSITE. 201 



Waste places. Penn. Muhl. July, Aug. 1|-. Heads with numerous purple 

 flowers. Involucre pale-brown, shining. Introduced from Europe. 



Brown Knap-weed. 



2. C. nigra Linn. : stem erect, branched ; leaves scabrous ; lower an- 

 gular-lyrate, petioled ; upper lanceolate ; scales of the involucre ovate, 

 fringed with capillary teeth ; rays none ; pappus very short, tufted. 



Fields. Mass, and Penn. July, Aug. l\..Stem 23 feet high. Heads 

 terminal, solitary. Flowers purple. Scales of the involucre almost black, the 

 teeth brown. Introduced from Europe and becoming in some places a trouble- 

 some weed. Black Knap-weed. 



3. C. Cyaniis Linn. : cottony-tomentose ; stem erect, branched ; upper 

 leaves linear, entire ; lowermost toothed or pinnatifid at base ; scales of the 

 involucre serrate ; pappus short. 



Cultivated grounds. N. S. July, Aug. (p. Stem 2 3 feet high. Heads 

 in terminal peduncles ; rays few, spreading, bright blue ; disk flowers smaller, 

 purple. Introduced from Europe and naturalized in a few places. 



Corn Blue-bottle. 



54. CNICUS. Vaitt. Blessed Thistle. 

 (From the Greek xvt^w, to prick or wound.) 



Heads many-floAvered ; the rays sterile, slender, nearly equal 

 to the disk. Involucre ovoid ; scales coriaceous, produced into 

 a long hard pinnated spinose appendage. Receptacle bristly. 

 Achenia smooth, striate. Pappus triple ; outer series very short ; 

 intermediate of 10 long rigid bristles ; inner of 10 short bristles. 



C. benedictus Linn. D. C. Centaurea benedicta. Linn. Ed. %. 



Road sides ; rare. N. Y. June. Torr. (J). Stem 1 2 feet high, branching. 

 Leaves clasping, somewhat decurrent and pinnatifid, the lobes spiny. Heads 

 large. Introduced. Common Blessed Thistle. 



55. ONOPORDON. Linn. Cotton Thistle. 



(From two Greek words expressive of the effect, ascribed by Pliny, to the ass 

 who eats the plant. Hook. Br. Fl.) 



Heads homogamous, many- and equal-flowered. Involucre 

 ovate-globose ; scales imbricate, coriaceous, terminating in a 

 lanceolate appendage bearing a spine at the summit. Recepta- 

 cle honey-combed. Achenia four-cornered, transversely ru- 

 gose. Pappus in several series, rough, deciduous. 



O. Acanthium Linn. : leaves ovate-oblong, sinuate and spinous, decur- 

 rent, woolly on both sides ; scales of the involucre linear-subulate, the 

 outer spreading and woolly at the base. 



Waste grounds. Mass. July. (). Stem 4 6 feet high, branched and 

 winged at the summit ; wings very spinous. Heads large, solitary. Flowers 

 purple. Introduced from Europe. Cultivated in Scotland as the Scotch Thistle. 



Common Cotton Thistle. 

 9* 



