172 DICOTYLEDONOUS PLANTS. 



HAB. Waste grounds. N. S. July, Aug. "U.Stem 3 4 feel 

 high. Leaves very large, cordate and wavy. Flowers numerous, 

 purple. As Dr. Bigelow remarks, " this plant intrudes itself on 

 every one's acquaintance by the sharp firm hooks at the end of 

 the calyx scales, which attach themselves to the clothes, and 

 serve as a remarkable mechanism for dispersing the seeds." In- 

 troduced. Burdock. 



11. CARDUUS. Linn. 



Involucre ventricose, imbricate, with spinous" scales. Re- 

 ceptacle hairy. Pappus pilose or plumose, deciduous. 



Syngenesia. JEqualte. 



* Leaves decurrent. 



1. C. lanceolatiis Linn. : stem hairy ; leaves decurrent, pinnatifid, 

 hispid ; the segments divaricate and spinous ; scales of the involucre 

 lanceolate, spreading. Cnicus lanceolatus Wittd. Cirsium lanceolalum 

 Spreng. 



HAB. Road sides. N. S. July Sept. tf.Stem, 24 feet 

 high. Leaves woolly beneath, the segments armed with long, 

 and acuto spines. Flowers terminal, purple, middle-sized. 



** Leaves sessile. 



2. C. altissimus Linn. : leaves sessile, oblong-lanceolate, scabrous, 

 tomentose beneath, dentate-ciliate ; radical ones pinnatifid ; involucre 

 ovate, bracteate ; scales ovate, lanceolate, spinous, appressed. Cnicus 

 altissimus WiUd. 



HAB. Old fields. Penn. to Car. June Sept. !. Stem 3 8 

 feet high, and on the Missouri, according to Mr. Nuttall, 12 18 

 feet. Flowers terminal, large, purple. 



3. C arvensis Linn. : stem paniculate ; leaves sessile, pmnalifid. 

 spinous ; involucre ovate or globose ; scales ovate-lanceolate, nmcron- 

 ate, appressed. Cnicus arvensis WWd. 



HAB. Fields and roads sides. N. S. July. !.- Root creeping. 

 Stem 2 3 feet high, many-flowered. Leaves very thorny. 

 Flowers terminal, small, purple. A very troublesome weed. 

 Introduced. Canada Thistle. 



4. C. muticus Nutt. : leaves all pinnatifid, woolly beneath; segments 

 spinulose, somewhat lanceolate, acute ; branches naked, 1 -lowered ; 

 involucre globose ; scales unarmed. Cnicus muticus Pursh. Cirgium 

 tnuticnm Mich. 



HAB. Mountains and low grounds. N. Y. to Car. Aug.. Sept.. 

 $ . Stem 2 4 feet high, branching above. Flowers purple* 

 middle-sized. Lower scales of the involucre spinous ; upper ones 

 simple, acute. C. glaber of Nuttall appears to be only a variety 

 of this species. 



5. C. virginianus mild. : stem attenuated, mostly 1 -flowered; leave* 

 sessile, lanceolate, margin revolute, distantly and spinosely serrate. 



