«> GENUS ARTEMISIA. 



Key to the Sections of Artemisia. 

 Heads heterogamous, marginal flowers pistUlate, disk-flowers hermaphrodite- 

 receptacle glabrous or pubescent. ' 



Disk-nowers fertile, ovary normal. 



Receptacle not hairy o„„_,„„ j ak. i / ..o\ 



Receptacle beset with numerous long hairs between disk-flowers; .•.•:;: Son H M^n^Zt & 



Ho P't'^-flo^ers sterile, ovary abortive; receptacle glabrous Sect on III DracuncX Fd 47i 



Heads homogamous by complete reduction of ray-flowers, disk-flowers aU her- ^^''"°''^''- ^'^'^^riculm (p. 47). 



maphrodite and fertile; receptacle glabrous Section IV. Seriphidium (p. 47). 



Key to the North American Species of Artemisia. 

 Section 1. Abrotanum. 

 (Ray-flowers present, disk-flowers present and fertile, receptacle glabrous.) 

 Heads with more than 10 flowers; leaves never cuneate and 3-toothed at apex, although 

 5. , , , sometimes spatulate and 3-cleft or 3-lobed. Herbs and shrubs 



Stems woody (decidedly so m the only native species, less woody m the 2 intro- 

 duced ones); leaves mostly dissected into fiUform lobes- 

 „ . . , , achenes angled, broad and truncate at summit. 



Pnncipal leaves 2 or 3 times pinnatifid. Introduced species. 



Leaves 3 to 6 cm. long, lobes slender, ascending; petiole naked 1 A abrotanum fn 4ql 



Leaves 1 to 3 cm. long, lobes short, spreadmg; petiole auricled at base. . . 2 A Znti<T(^ %) '' 



Pnncipal leaves mostly once pinnatifid. Native species 3 J Sfo^i^ (n m 



Stems herbaceous, sometimes a Uttle woody at base; leaves entire or variously cut ""''J^^'^ (P- 53). 



but seldom with truly filiform lobes; achenes smooth or ribbed 

 ™ . . , ,Dut scarcely angled, mostly with slight incurving at summit. 



i-lant perennial, stems from a rootstock or caudex; leaves various 

 Foliage not tomentose beneath but silvery-canescent, villous, or glabrous- 

 stems 6 dm. or less high. Subalpine and Arctic plants with 

 dissected leaves. 

 Disk-coroUas 2.5 to 3.5 mm. long (smaller in some forms of No. 4); heads 5 

 to 9 mm. broad, except in senjavinensis and norvegica glomerata 

 begments of leaves strongly divergent, primary divisions at right-angles to 



Segments of leaves pointing forward ^- ^- ""^"^^^^^ (P- 56). 



Leaf-lobes longer than their hairs, or leaves glabrous; lower leaves 



usually 2 or 3 times cleft or divided 5 ^ norveoica (r, 'i7^ 



Leaf-lobes exceeded and neariy concealed by their long villous pub^l ' ' """^^"^ ^P" ^'^- 



Disk-corollas (p. t "^t^^t^^^"^-^..^ ' Southem' Rocky '^ ^^ ''""""^-^ '^^ '''■ 



„ , Mountains 7 A t^tt,,,- Cr, fifi^ 



Fohagemoreorlesstomentosebeneath, usually denselyso;stems3to30dm" high ^' 



Disk-coroUas 3.5 to 4 mm. long; involucre 6 to 7 mm. high. A white- 

 Disk rornlI«, ^°"f "^"'^ ''^'i'^ "^'^^ ^^7 large heads and thick obtuse leaf-lobes. 8. A. stelleriana (p. 67). 

 uisk-corolias 1.5 to 3 mm. long; involucre 2.5 to 5 mm. high 



Leaves (except the uppermost) twice dissected and lobes obtuse; disk-flowers 

 45 to 90. 



Heads not secund; leaf-lobes linear; involucre 5 mm. high 9. ^ alaskana (d 68) 



Heads '^ec^'^ld^y^secund; leaf-lobes elliptic or oblanceolate; involucre 2.5 '"°««»"<' ^P- ^SJ- 



Leaves vari£usl£cutj-^entire but lobes always acute; isk-flow'e^^ ^°' ^- ■^^'""*^''^" (P- 69)- 



Plant annual or biennial, with taproot; stem erect; leaves 2 or 3 times pinnateiy "' ^' "^""^ ^^' ^^^' 

 parted or divided. -^ 



Leaves green; divisions not filiform. 



Involucre 2 to 3 mm. high; inflorescence a dense compound spike; heads 



crowded, erect 12 ,4 hi^r,i, Cn ini ^ 



Involucre 1 to^^^S^mm. high; inflorescence a loose panicle;' heads ioose; often ^^' ^■ 



Heads ^'tronTv"2';nTfl"!°"?'^i^'^*°°'?i^°T^-- Mexicanspecies with dense panicies". U. 1 IZZhFan^^fl 103). 

 Heads with only 2 to 4 flowers; leaves at least m part cuneate and 3-toothed at sum- 



mit. Low shrub 15_4_ bi^.^^. (p j^^j 



Section II. Absinthium. 

 (Ray-flowers present, disk-flowers present and fertile; receptacle villous.) 

 Stem 4 to 10 dm. high; divisions of leaves oblong or oblanceolate, ultimate segments 



'1>Tan\*;o' r- Y^ frf'/^^iell'er.inear,- ultimate-segments about 1 mm! wide. ''^ ^^ ""'"''''''''^ '^^ ''''■ 



solitary. 

 Heads 5 to 25, 4 to^6 mm. broad; disk-flowers 15 to 30; leaves mostly twice pin- 

 Heads 1 to 5, 5 to 7mm. broad; ■disk:flowers30 to' 120; leavesonce pinnateiy divided ^^- ^" '"^^P^"™'" (P- "o>- 



°' ^'^f* 19. A. pattersoni (p. 112). 



