CIpMPOSIT^. 195 



and scarious on *tlie 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 ; 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- Hnear-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. (1). — Stem mostly erect, but sometimes decumbent at base, 2 — 4 feet high. 

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

 terminal paniculjJte racemes. A variable species. Wild Wormwood. 



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

 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. @. — 

 Stem 2 — 6 feet high, rather slender. Leaves shghtly 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 villous. 



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

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

 spheric, in leafy paniculate racemes, nodding. 



Road sides. N. S. Aug. 'l\.. — Stem^2 — i 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.— Ta^nsy. 



(The name altered from Athanasia ; a, not, and davaros, 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- 



.^ * 



