356 LXXV. COMPOSITE. CIRSIUM. 



having earth heaped up around it, and then the petioles become tender, crisp, 

 eatable, like celery. Aug. Sept. 



69. CIRSIUM. Tourn. 

 Gr. Ktpvos, a swelling of the veins, which this plant was supposed to heal. 



Heads discoid, homogamous ; involucre subglobose, of many rows 

 of spinose-pointed, imbricated scales ; receptacle bristly ; style scarqe- 

 ly divided ; pappus copious, plumose ; achenia compressed, smooth. 

 Herbs with alternate leaves , generally armed with spinose prickles. Fls. 

 cyanic. 



1. C. ARVENSE. Scop. (Cnicus arvensis. Ph.} Canada Thistle. 



Lvs. sessile, pinnatifid, spinous; st. panicled; invol. round or ovate, witn 

 minute spines, scales close-pressed, ovate-lanceolate. 9^ A very common this- 

 tle in fields, roadsides and waste places, N. Eng. to Ohio. It is one of the 

 severest pests of the farmer, requiring his constant vigilance to extirpate it from 

 his fields. In England it is called cwsed thistle. Root creeping, very long and 

 exceedingly tenacious of life. Stem 3f high, with a branching panicle at top. 

 Leaves alternate, thickly beset with thorns. Heads rather small, purple, the 

 involucre nearly thornless, and is the only part of the plant that can be safely 

 handled. July. 



2. C. DISCOLOR. Spreng. (Cnicus discolor. MM.} Tall Thistle. % 

 Lvs. sessile, pinnatifid, rough-haired, downy beneath, the segments 2-lobed, 



divaricate, spinose; invol. globose, the scales ovate, appressed, with spreading 

 spines at the tips. (g) A slender thistle, 3 5f high, much branched, and leafy 

 at the summit. Found in thickets, N. Eng. to ill. Heads terminating the 

 branches, an inch in diameter, with reddish-purple corollas. July, Aug. 



3. C. MUTICUM. Michx. (Cnicus glutinosus. Bw.} Glutinous Thistle. 



* Lvs. pinnatifid with divaricate segments ; invol. ovate, with unarmed, 

 villous-arachnoid, glutinous scales. (g) A fine looking thistle found in damp 

 soils, Can. and U. S. Stem branching, 3 7f high. Leaves armed with spines 

 at each angle. Heads ' diam., with xleep purple corollas, the scales webbed 

 and glutinous on the back. Aug. Sept. 



4. C. HORRIDULUM. Michx. (Cnicus horridulus. Linn.} Yellow Thistle. 



Lvs. sessile, pinnatifid, acutely cut, spinose; hds. invested with an exter- 

 nal involucre of about 20 ve r y spinose bracts; scales unarmed. (g) Found in 

 meadows and hills, N. Eng. to Flor. The stem is 1 3f high, invested with 

 wool. Leaves somewhat clasping, woolly and hairy, armed with stfff spines. 

 Heads large, with yellowish- white corollas surrounded by a whorl of lanceolate 

 or linear leaflets tipped with stiff thorns, the scales webbed. Aug. 



5. C. PUMILUM. Spreng. (Cnicus odoratus. MiM.} Pasture Thistle. 

 Hairy; Lvs. green on both sides, clasping, oblong-lanceolate, pinnatifid, 



the segments irregularly lobed, ciliate, spinose; invol. round-ovate, spinose, 

 naked. (g) A common, low, turgid thistle in roadsides, pastures, N. Eng. and 

 Mid. States. Stem 1 2f high, stout, striate, with 1 3 very large heads of 

 fragrant, purple flowers. Aug. 



6. C. LANCEOLATUM. Scop. (Cnicus. Ph. Carduus. Linn.} Common Thistle. 

 Lvs. decurrent, pinnatifid, hispid, the segments divaricate and spinose ; 



invol. ovate, villous; scales lanceolate, spreading. (g) Common in borders of 

 fields, roadsides, N. Eng. and Mid. States, always distinguished by the decur- 

 rent leaves. Stem 3 4f high, winged by the decurrent leaves which are white 

 and woolly beneath, armed with formidable spines at all points. Fls. numerous, 

 large, purple. Involucre scales webbed, each ending in a spine. July Sept. 



7. C. ALTISSIMUM. Spreng. (Carduus. Linn. Cnicus. Willd.} 



Tall, branched, viilose-pubescent, leafy; Ivs. whitish beneath, spinose- 

 ciliate, sessile, lanceolate-oblong, sinuate-dentate, lower ones pinnatifid, petio- 

 late; lobes or leet/i spinescent ; invol. ovoid-oblong; scales close-compressed, ovate- 

 lanceolate, outer ones with a spreading spine at apex. Fields and barrens, 

 Perm, and Western States ! common. Stem 3 8f high. Leaves 6 8' by 1 6'. 



