48 GENUS ARTEMISIA. 



Artificial Key to the North American Species of Artemisia — Continued. 



Foliage silky-pubescent to glabrous, never woolly or tomentose; leaf- 

 lobes lanceolate or elliptic. 

 Disk-corollas 2.5 mm. or more long (rarely shorter in the Alaskan 

 macrobotrys) . 



Segments of leaves strongly divergent 4. A. macrohotrys (p. 56). 



Segments of leaves pointing forward. 



Leaf-lobes not concealed by their hairs 5. A. norvegica (p. 57). 



Leaf-lobes entirely hidden among their long villous hairs Q. A. senjavinensis (p. 65). 



Disk-corollas 2 mm. or less long. Southern Rocky Mountains 7. A. parryi (p. 66). 



Receptacle densely long-hairy between the flowers. 



Stems very leafy; heads usually in panicles. Middle and lower altitudes. ... 17. A. frigida (p. 108). 

 Stems sparsely leafy; heads in racemes or solitary. Alpine and subalpine. 



Heads 5 to 25; leaves mostly twice pinnatifid 18. A. scopvlorum (p. 110). 



Heads 1 to 4; leaves only once pinnatifid or cleft 19. A. pattersoni (p. 112). 



Plant a shrub, sometimes low but always decidedly woody at base. 

 Leaves (except sometimes the uppermost ones) pinnately lobed or pinnatifid, ulti- 

 mate divisions mostly linear. 

 Lobes of at least most of leaves again divided or dissected. 

 Receptacle not hairy. 



Inflorescence a panicle; leaves twice pinnatifid. Introduced. 



Leaves green above 1. A. abrotanum (p. 49). 



Leaves white on both sides 2. A. ponlica (p. 52). 



Inflorescence raceme-like; leaf-divisions ternately cleft. Alaskan 9. A. alaskana (p. 68). 



Receptacle thickly beset with long woolly hairs between flowers. 



Plant 5 to 10 dm. high; divisions of leaves lanceolate. Introduced 16. A. absinthium (p. 106). 



Plant 1 to 4 dm. high; divisions of leaves narrowly linear. Native . 17. A. frigida (p. 108). 



Lobes of leaves mostly entire. 



Central flowers without subtending bracts. 



Foliage gray with a close pubescence. Coastal shrub 5 to 25 dm. high 3. A. califomica (p. 53). 



Foliage green, glandular; dwarf plant of the Great Basin 28. A. pygnmea (p. 154). 



Central flowers mostly subtended by conspicuous bracts of receptacle. Large, 



coastal plant 29. A. palmeri (p. 155). 



Leaves either entire or palmately toothed or cleft from summit. 



Shrub very spiny; corollas copiously long-hairy 24. A. spinescens (p. 132). 



Shrub not spiny; corollas not hairy. 



Principal leaves entire or rarely with a few teeth or lobes, linear, somewhat 



tapering to each end 26. A. cana (p. 150) . 



Principal leaves (that is, all but uppermost entire ones) toothed or cleft or 

 parted at summit (often spatulate or filiform). 

 Lobes or teeth of leaf plane, not filiform or thread-like. 



Inflorescence a spike, raceme, or panicle with at least upper heads longer 

 than their subtending bracts. 

 Heads in panicles; shrub 1 to 20 dm. high; leaves toothed or cleft but 

 never more than halfway down. 



Panicles loosely branched; flowers all alike in the head 25. A. tridentata (p. 135). 



Panicles closely branched, heads glomerate; corollas of outer flowers 

 much reduced and without stamens. Southern Rocky Moun- 

 tains 15. A. bigelovi (p. 104). 



Heads in racemes; shrub 0.5 to 1.5 dm. high; leaves divided nearly to 



base into usually 3 lobes 23. A. pedatifida (p. 131). 



Inflorescence consisting of solitary heads sessile in the axils, all much 



exceeded by their subtending bracts or leaves 27. A. rigida (p. 153). 



Lobes of the leaf filiform (thread-hke). 

 Achenes narrow at summit; heads 3- to 9-flowered. Nebraska and Texas 



to Chihuahua and Nevada . 22. A. filifolia (p. 130). 



Achenes broad at summit; heads 20- to 50-flowered. Coast of California 



and Lower CaUfomia 3. A. califomica (p. 53). 



