A. VULGARIS. 71 



from entire to twice dissected, the upper surface glabrous to densely and permanently 

 white-tomentose, the lower surface always white-tomentose; inflorescence paniculate, 

 10 to 40 cm. long, usually 2 to 8 cm. broad but sometimes reduced to a spike only 1 cm. 

 broad or again with spreading branches and then up to 15 or 20 cm. broad; heads hetero- 

 gamous, short-peduncled or sessile, nodding or erect; involucre campanulate to ovoid, 

 3 to 5 mm. high, 2 to 8 mm. broad; bracts 7 to 16, ovate or broadly elliptic, obtuse, with 

 pale or light-brown scarious margins, densely tomentose to glabrous; ray-flowers 4 to 10, 

 fertile, corolla narrowed and irregularly toothed above, 1.5 to 2 mm. long, glabrous or 

 resinous-granuliferous; disk-flowers 3 to 50, fertile, corolla funnelform, 1.5 to 3 mm. long, 

 5-toothed, glabrous or only resinous-granuliferous; style-branches truncate or obtuse, 

 those of the disk-flowers dilated and erose at summit; achenes ellipsoid, not nerved or 

 angled, glabrous but often resinous-glandular. 



Almost throughout North America; common also in the Old World. 



SUBSPECIES. 



No other Artemisia has such a multitude of variations as A. vulgaris. Many of these 

 result from environmental influences; in others, individual variation is so great that a taxo- 

 nomic analysis becomes impossible. The American forms may be assembled into 15 sub- 

 species, as follows: 



Key to the Subspecies of Artemisia vulgaris. 

 Involucre 4 to 5 mm. high, 4 to 8 mm. broad; disk-flowers 20 to 50. Northwestern forms. 

 Foliage green above, densely white-tomentose beneath; involucre sparsely tomentose, 



greenish ; (a) tilesi (p. 72). 



FoUage white-tomentose on both sides, sometimes less densely so above; involucre 



densely tomentose ■ • • (b) candicans (p. 73). 



Involucre 3 to 4 mm. high, 2 to 4 mm. broad; disk-flowers 3 to 20, or occasionally to 25 (in 

 heterophylla and longijolia, and even to 50 in discolor, which con- 

 nects through large-headed forms with tilesi). 

 Divisions of lower leaves again toothed cleft or lobed; divisions of middle stem-leaves 

 also usually toothed or cleft. 

 Leaves green and nearly glabrous above, white-tomentose beneath. 



Primary divisions of leaves 5 to 15 mm. wide, directed forward (c) typica (p. 73). 



Primary divisions of leaves less than 5 mm. wide, spreading. 



Panicle 5 cm. or less broad, compact; heads mostly 20- to 50-flowered (d) discolor (p. 74). 



Panicle 10 to 15 cm. broad, with spreading leafy branches; heads 15- to 20- 



flowered (e) redolens (p. 75). 



Leaves white-tomentose on both sides (/) flodmani (p. 75). 



Divisions of ail the leaves entire or nearly so or leaves themselves entire. 

 Leaves ample, principal ones 1 to 2.5 cm. or more wide, with a few prominent lanceo- 

 late lobes, varying to entire, upper surface green; involucre 3 to 4 

 mm. high. 

 Disk-flowers 9 to 23; involucre campanulate, 2.5 to 3.5 mm. broad, densely 



tomentose (g) heterophylla (p. 76). 



Disk-flowers 3 to 7; involucre ovoid, 2 to 2.5 mm. broad, nearly glabrous (A) litoralis (p. 76). 



Leaves narrow, 1 cm. or less wide exclusive of lobes when present, divisions also nar- 

 row, upper surface either green or gray-tomentose; involucre rarely 

 over 3 mm. high except in subspecies gnaphalodes and longifolia. 

 Principal leaves entire or variously toothed, cleft, or rarely divided but the lobes 

 not slender and elongated (except in a rare form of longifolia, with 

 lobes caudate-attenuate). 

 Inflorescence plainly paniculate, 1.5 cm. or more broad. 

 Margins of leaves not evenly serrate. 



Upper surface of leaves more thinly tomentose than lower or at length 



glabrate and green (i) ludoviciana (p. 76). 



Upper surface of leaves densely white-tomentose hke lower, tomentum 

 usually persistent (exceptions in longifolia are recognized by the 

 caudate leaves). 

 Involucre 3 to 3.5 mm. high; leaves not verj' slender, entire or with 



comparatively short lobes U) gnaphalodes (p. 77). 



Involucre about 4 mm. high; leaves slender and elongated, often caudate- 

 attenuate, entire or divided into similarly elongated lobes (k) longifolia (p. 78). 



Margins of leaves evenly serrate (') serrata (p. 79). 



Inflorescence a narrow spike-like panicle 1 cm. or less broad. A low plant, 

 often woodv below, with narrow leaves inchned to be entire or only 



shghtly lobcd (m) Undleyana (p. 79). 



Principal leaves mostly divided into slender elongated or linear-filiform lobes 

 4 mm. or less wide. 



Leaf-lobes mostlv 2 to 4 mm. wide (n) mexicana (p. 80). 



Leaf-lobes 0.5 to" 1 mm. wide (o) wrighti (p. 80). 



