GENUS 94. 



THISTLE FAMILY. 



523 



7. A. 



8. A. 



** Marginal flowers pistillate; central flowers perfect, fertile. 



a. Receptacle villous-pubescent. 

 Leaf-segments linear-filiform, short ; native. 

 Leaf-segments oblong, or linear-oblong ; introduced. 



b. Receptacle glabrous, or sparingly pubescent. 

 Leaves dissected, glabrous or pubescent, green, not tomentose. 



Heads about 2" broad, numerous in panicled racemes ; perennial. 

 Heads about i" broad, paniculate or spicate ; annuals. 

 Leaves finely 2-3-pinnately divided ; heads paniculate. 

 Leaves pinnately divided ; segments pinnatifid ; heads in leafy spikes. 

 Leaves densely white-canescent or tomentose, at least beneath. 

 Leaves pinnatifid or dissected. 



Heads 3" 4" broad, racemose-glomerate; sea-beach plant.' 

 Heads \"-2." broad, spicate-paniculate or racemose. 



Leaves deeply pinnatifid, the segments mostly incised. 

 Leaves finely dissected into short linear lobes. 

 Leaves pinnately parted into 5-7 narrow entire segments. 

 Leaves lanceolate or linear, serrate or entire, not pinnatifid. 

 Leaves lanceolate, sharply serrate, glabrous above. 

 Leaves linear, oblong, lanceolate or obovate, entire or lobed. 

 Leaves at length glabrous above. 



Leaves linear, elongated, all entire. 



Leaves various, at least the lower pinnately lobed or toothed. 

 Involucre densely woolly ; leaf-lobes broad. 

 Involucre loosely woolly ; leaf-lobes linear. 

 Leaves shorter, oblong or lanceolate, tomentose both sides. 

 Leaves cuneate, j' long, 3-toothed at the apex. 



*** Flowers all perfect and fertile; far western species. 



Leaves cuneate, 3-toothed or 3-lobed. i 22. A. 



Leaves linear, entire. 23 



frigid a. 

 Absinthium. 



9. A. Abrotanum.- 



10. A. annua. 



11. A. biennis. 



12. A. Stellariana. 



13. A. 



14. A. 

 15 



A. 



vulgaris. 

 Pontica. 

 kansana. 



1 6. A. serrata. 



17. A. longifolia. 



18. A. 



19. A. 



20. A. 



21. A. 



A. 



ludoviciana. 

 mexicana. 

 gnaphalodes. 

 Bigelovii. 



tridentata. 

 cana. 



i. Artemisia caudata Michx. Tall or Wild 

 Wormwood. Fig. 4571. 



Artemisia caudata Michx. Fl. Bor. Am. 2: 129. 1803. 



Root biennial (sometimes perennial?) ; stems slender, 

 glabrous, tufted, strict, very leafy, 2-6 high, at length 

 paniculately branched, the branches glabrous, or rarely 

 slightly pubescent, nearly erect. Lower and basal leaves 

 and those of sterile shoots slender-petioled, sometimes 

 a little pubescent, 3 '-6' long, 2-3-pinnately divided into 

 narrowly linear, acute lobes, about i" wide ; upper leaves 

 sessile or nearly so, pinnately divided, or the uppermost 

 entire and short; heads about i" broad, very short- 

 peduncled, very numerous in a large somewhat leafy 

 panicle, mostly nodding; bracts of the ovoid-campanu- 

 late involucre ovate, or the inner elliptic, glabrous ; re- 

 ceptacle hemispheric, naked; central flowers sterile. 



In dry sandy soil, abundant on sea-beaches, from Quebec 

 to Florida, west to Ontario, Indiana, Manitoba, south to 

 Nebraska and Texas. July-Sept. 



2. Artemisia borealis Pall. Northern Worm- 

 wood. Fig. 4572. 



Artemisia borealis Pall. Iter. 129. pi. hh, f. I. 1771. 

 Artemisia groenlandica Wormsk. Fl. Dan. pi. 1585. 1818. 



Perennial, S'-is' high, densely silky-pubescent all 

 over, resembling small forms of the following spe- 

 cies. Leaves less divided, the basal and lower ones 

 petioled, i'-2i' long, the upper sessile, linear and 

 entire or merely 3-parted; heads about 2" broad in 

 a dense terminal rarely branched thyrsus ; involucre 

 nearly hemispheric, its bracts brown or brownish, 

 pilose-pubescent or nearly glabrous; receptacle con- 

 vex, naked ; disk-flowers sterile. 



Quebec to Greenland, west through arctic America to 

 Alaska, south in the Rocky Mountains to Colorado. Also 

 in northern Asia. Apparently erroneously recorded from 

 Maine. July-Aug. 



