A. CAMPESTRIS. 121 



below, or reduced in northern and high-mountain forms to a nearly simple spike, 5 to 50 

 cm. long, 1 to 15 cm. broad; heads heterogamous, sessile or short-peduncled, erect or 

 nodding; involucre hemispheric, 2 to 4 mm. high, about as broad; bracts 8 to 20, round- 

 elliptic, obtuse or subacute, light brown or yellowish green with a brown medial line, 

 scarious-margined, densely villous to glabrous; receptacle naked; ray-flowers 5 to 20, 

 fertile, corolla 1 to 1.5 mm. long, narrowed above; disk-flowers 6 to 30 or perhaps 40, 

 sterile, corolla campanulate, 1.5 to 3 mm. long, regularly 5-toothed, yellowish-white or 

 often purplish above, glabrous or the teeth pubescent; style of disk-flowers 1.5 to 3 mm. 

 long, either undivided and erose around the cup-shaped summit or slightly cleft into more 

 or less spreading branches; achenes subcylindric, glabrous, those of the disk-flowers 

 abortive. 



On the plains and in the mountains almost throughout North America except in the 

 desert districts: Greenland, Hudson Bay, and the Atlantic seaboard to Florida, Texas, 

 New Mexico, California (along the northern coast only), Oregon, and Alaska; also in Asia, 

 Europe, and northern Africa. 



SUBSPECIES. 



No less than 17 American forms of this species have been segregated by various 

 botanists and dignified with specific rank; 13 are recognized in the North American Flora. 

 Some of these segregates are strikingly unlike in appearance, yet all are held in one natural 

 group by a remarkable uniformity in all essential characters. The varietal differences 

 are chiefly those of duration (with its resulting differences in branching), number of 

 flowers (with differences in the size and shape of the head), and nature or amount of the 

 pubescence. For present purposes it seems necessary to recognize but 6 of the variations, 

 and these are here given subspecific rank. Other segregates are minor variations of 

 these. 



Key to the Subspecies of Artemisia eampestris. 



Involucre mostly 2 to 3 or rarely 3..5 mm. high, 2 to 3.5 mm. broad; root either biennial 

 or perennial. 

 Plant perennial; stems usually several. 



Inflorescence open-paniculate; heads nearly ovoid; leaves moderately pubescent, 



glabrate (a) typica (p. 121). 



Inflorescence densely paniculate; heads nearly hemispheric at maturity; leaves 



densely and permanently pubescent (b) pacifica (p. 122). 



Plant biennial; stem usually single (c) caudala (p. 122). 



Involucre 3 to 4 mm. high, 3.5 to 5 mm. broad; root strictly perennial. 

 Pubescence when present appressed and silky. 



Involucre glabrous or nearly so; divisions of leaves linear or very narrowly ob- 



lanceolate (d) borealis (p. 122). 



Involucre densely villous; divisions of leaves often linear-oblanceolate (e) spilhamaea (p. 123). 



Pubescence loosely silky-villous, very dense and extending to all parts. Pacific coast. (J) pycnocephala (p. 123). 



21o. Artemisia campestris typica. — Root perennial; stems usually several, 3 to 5 

 dm. high, very leafy at base, sparsely leafy above; leaves mostly twice pinnately divided 

 into linear or linear-filiform divisions about 0.5 mm. wide, the upper less divided or entire, 

 all pubescent at first but often glabrate; inflorescence openly paniculate, 3 to 15 cm. 

 broad, the branches few and spreading; heads nodding, ovoid when young, expanding 

 in age to hemispheric; involucre 2 to 3 mm. high, about 2.5 mm. broad, glabrous; disk- 

 flowers 5 to 12, the corolla 1.8 to 2.5 mm. long. {A. campestris Linnaeus, Sp. PI. 846, 

 1873.) Abundant on the plains of Europe and western Asia; occasionally found on the 

 Atlantic Coast of North America, where perhaps introduced. Type locality, Europe. 

 Collections: Marthas Vineyard, Massachusetts, August, 1888, Burgess (no roots but 

 inflorescence open); Naugatuck, Waterbury, Connecticut, July 14, 1903, Bristol (Gr); 

 Aiken, South Carolina, Eggleston 5063 (NY, probably this subspecies, although without 

 root). 



