COMPOSITE. 69 



2. C. dis'color, Spreng. (Cnicus altissimus, Willd., var. dis- 

 COlor, Gray, in Macoun's Catalogue.) The inner scales of the 

 involucre not prickly. Stem grooved. Leaves prickly, green 

 above, white-woolly beneath. Flowers pale purple. Whole plant 

 with a whitish aspect. Dry thickets. 



3. C. mil'ticum, Michx. (Cnicus muticus, Pursh, in Macoun's 

 Catalogue.) (SWAMP THISTLE.) Scales of the webby involucre 

 hardly prickly, and not spreading. Stem very tall, and smoothish, 

 and sparingly leafy. Heads single or few. Swamps and low 

 woods. 



4. C. arvense, Scop. (Cnicus arvensis, Pursh, in Macoun's 

 Catalogue.) (CANADA THISTLE.) Scales of the involucre with 

 reflexed points. Leaves prickly, smooth both sides, or slightly 

 woolly beneath. Roots extensively creeping. Heads small and 

 numerous. Fields and roadsides. 



3. ONOPOR'DON, Vaill. SCOTCH THISTLE. 



0. acan'thium, L. A coarse branching herb, 2-4 feet high, 

 with woolly stem and leaves. Bristles of the pappus united at 

 the base into a ring. Roadsides and old fields ; not common. 



3. LAP'PA, Tourn. BUBDOCK. 



L. oflicina'lis, All., var. major, Gray. (Arctium Lappa, L., 

 in Macoun's Catalogue.) A coarse plant with very large cordate 

 petioled leaves, and numerous small globular heads of purple 

 flowers. The involucre forms a bur which clings to one's cloth- 

 ing, or to the hair of animals. Near dwellings, mostly in 

 manured soil. 



4. CENTAURE'A, L. STAB-THISTLE. 



C. Cy'anUS, L. (BLUE-BOTTLE.) An old garden plant, found 

 occasionally along roadsides. False rays very large. Scales of 

 the involucre fringed. Leaves linear, entire or nearly so. Stem 

 erect. Heads single at the ends of the branches. 



5. XAJV'THIUM, Tourn. CLOTBUB. 



1. X. struma'rium, L., var. echina'tum, Gray. (X. Cana- 



dense, Mill, var. echinatum, Gray, in Macoun's Catalogue.) 

 (COMMON COCKLEBUR.) Stem rough, not prickly or spiny. 



