COMPOSITE. 195 



and scarious on the margin. Receptacle flattish or convex, 

 naked or villous. Achenia obovate, with a minute epigynous 

 disk. Pappus none. 



* Receptacle naked. 



1. A. vulgaris Linn. : herbaceous, erect ; leaves white-tomentose be- 

 neath ; cauline pinnatifid ; segments laciniate, incised, coarsely serrate and 

 entire ; uppermost nearly linear, entire ; heads ovoid, at length erect 5 outer 

 scales of the involucre white-tomentose. 



Banks of streams. Arct. Amer. Ver. and N. Y. S. to Car. Sept., Oct. %.. 

 Stem 2 3 feet high, suflruticose, much branched. Leaves variable. Heads few, 

 sessile. Introduced ? Mugwort. 



2. A. Canadensis Mich. : smooth or canescent ; lower leaves pinnate, 

 petioled ; upper subpinnate, sessile ; segments linear or linear-lanceolate ; 

 heads hemispheric, in paniculate racemes ; scales of the involucre roundish 

 or ovate, scarious on the margin. 



Sandy shores. Mass, and N. Y. N. to the Arctic Circle. W. to Oregon. July, 

 Aug. fl\ Stem mostly erect, but sometimes decumbent at base, 2 4 feet high. 

 Radical leaves clustered, silky beneath. Heads rather large, very numerous, in 

 terminal paniculate racemes. A variable species. Wild Wormwood. 



3. A. cor data Mich.: stem erect, smooth; radical and lower cauline 

 leaves sub-bipinnate, upper sub-pinnate ; segments subsetaceous, alternate, 

 somewhat divaricate ; racemes elongated, erect, paniculate ; heads sub- 

 globose. A. Canadensis Big. 



Sandy woods and shores. N. H. to Geor. W. to Miss. Aug., Sept. (g). 

 Stem 2-6 feet high, rather slender. Leaves slightly pubescent beneath, petioled 

 or sessile. Heads erect, very numerous, in racemes which form a dense pyram- 

 idal panicle. Nearly allied to the preceding. Tall Wormwood. 



** Receptacle vittov,s. 



4. A. Absinthium Linn.: suffYuticose, erect, silky-canescent ; leaves bi- 

 pinnatifid ; the segments lanceolate, often incised, obtuse ; heads hemi- 

 spheric, in leafy paniculate racemes, nodding. 



Road sides. N. S. Aug. 'ZJ-. StemsZ 4 feet high, several from one root. 

 Heads numerous. Flowers yellowish. Introduced and naturalized in a few 

 places. Uncommonly bitter, and valuable for its medicinal properties. 



Common Wormwood. 



45. TANACETUM. Linn. Tansy. 



(The name altered from Athanasia ; a, not, and 6avaros, death ; because its 

 flowers do not quickly fade.) 



Heads homogamous or heterogamous, with pistillate flowers 

 in a single series in the circumference, often 3 4 -toothed. 

 Disk-flowers 4 5 -toothed. Receptacle naked, convex. Invo- 

 lucre campanulate, imbricate. Achenia sessile, angular, smooth, 

 with a large epigynous disk. Pappus none or minute, membra- 

 naceous and crown-form, entire or toothed. 



T. vulgare Linn. : stem herbaceous, erect, smooth ; leaves smoothish, bi- 



