268 A GUIDE TO THE WILD FLOWERS 



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821. Common Thistle. Cirsium lanceolatum. A stout 

 branched, more or less white-hairy European biennial, 3-5 

 ft. high. Leaves lance-shaped, 3-6 in. long, very prickly, more 

 or less deeply cut, the segments bristle-toothed, brown-hairy 



"on the under surface. Flower heads prickly, dark purple, in, 

 a sparse, leafy cluster, or solitary, and with a few small 

 prickly leaves below each head. In waste places, Newfound- 

 land to Georgia and westward, July-November. Fig. 821. 



822. Field Thistle. Cirsium discolor. A rather close native 

 relative of No. 821, but the leaves white-hairy on the under 

 side, and the flower heads merely bristly. In fields and road- 

 sides. New Brunswick and Ontario to Georgia, and westward. 

 July-November. A related plant, C. altissimiim, has prickly, 

 but undivided leaves, and is found from Mass. to Florida 

 and Texas. 



823. Yellow Thistle. Cirsium horridulum. (C. spinosissi- 

 mum.) A coarse, very prickly weed, somewhat woolly when 

 young, but green in maturity. Leaves green both sides, lance- 

 oblong, cut or deeply lobed, prickle-tipped, 2-6 in. long. 

 Flower heads solitary, or few, 1-4 in. long, pale yellow. In 

 dry places, Maine to Florida, and westward. July. Fig. 823. 



824. Canada Thistle. Cirsium arvcnse. One of the com- 

 monest European weeds in northeastern America, usually 

 branched, 1-3 ft. high. Leaves green both sides, stalkless, 

 prickly, much cut into prickle-tipped lobes, 5-8 in. long, 

 lance-oblong. Flower heads numerous, in branched clusters, 

 the heads less than i in. wide, and purplish-white. In fields 



