THISTLE FAMILY 963 



Plant decidedly pubescent. 5. A. Forwoodii. 



Perennials, with a rootstock or caudex; heads nodding at least at first. 

 Plant 3-10 dm. high; stem leafy. 



Stem tall, very leafy, 4-10 dm. high; bracts acute or acutish. 



6, A. pnciflca. 

 Stem lower, 3-5 dm. high; stem-leaves rather small and scattered; bracts 

 obtuse or rounded at the apex. 7. A. camporum. 



Plant less than 1 dm. high; stem scapiform; stem-leaves minute. 



18. A. minula. 

 Heads larger, 4-5 mm. broad, not very numerous (except in A, Bourgeauana), in narrow 



spike-like panicles; plants low, rarely 3 dm. high. 

 Involucral bracts glabrous or nearly so; disk-corollas glabrous. 



8. A. MacCallae. 

 Involucral bracts more or less villous ; disk-corollas usually with a few hairs on the 



lobes. 

 Plant 3-4 dm. high; heads very numerous, in a dense panicle. 



9. A, Bourgeauana. 

 Plant 1-3 dm. high; heads fewer, usually a spike-like panicle or racemose. 



10. A. spithamaea, 



II. FiLIFOLlAE. 



Taller shrubs, 3-10 dm. high, with numerous heads in leafy panicles; heads 3-7-flowered. 



11. yl. fiii folia. 



Low undershrubs, less than 1.5 dm. high, with racemose inflorescence; heads 10-15- 



flowered. 

 Leaves ternate or bitemate. 12. A. peaatifida. 



Leaves pinnatifld with 5-7 divisions. 18. A. minuta. 



III. Frigidae. 



Plant tall, 6-10 dm. high, erect; leaves twice or thrice pinnatifld. 13. A. Absinthium. 

 Plant lower, 2-4 dm. high, often decumbent at base; leaves twice ternate. 



14. A. frigida. 



IV. Lanatae* 



Basal leaves twice pinnatifld into linear divisions; stem-leaves pinnate; heads 5-12. 



15. A. scopuloTum. 

 Basal leaves pinnatifld into 3-5 linear-oblanceolate approximate divisions; stem-leaves 



ternately cleft or entire; heads 1-4. 16. A. Pattersonu 



V. AxmiAE. 



One species. 17. A. biennis. 



VL NORVEGICAE. 



Heads 6-10 mm. broad, usually more than 40-flowered; corollas hairy or rarely glabrous; 



bracts with fuscous margins. , - , 



plant more or less pubescent, at least on the leaves and peduncles. ^ 



Plant silvery-silky; bas'alleaves 6 cm. long or less, pinnatifld or bipmnatifld with 



few divisions. , . , , t. . - , . 



Plant less than 1 dm. high; leaves 1-1.5 cm. long; involucral bracts with in- 

 conspicuous light brown margins, slightly tomentose, soon glabrous. 



18. A. minuta. 



Plant 1-3 dm. liigh; leaves 2-6 cm. long; involucral bracts with conspicuous 

 dark brown or blackish scarious margins. 19. A. Tyrrellii. 



Plant green' leaves twice pinnatifld, the basal ones more than 1 cm. long. 



Leaves and stem decidedly hairy; inner bracts ovate, acute, with narrowly 



lanceolate green center. , , 20. A. saxicola. ^ 



Leaves sparingly pubescent or glabrate; stem glabrous or nearly so; inner 

 bracts obovate, obtuse or rarely acutish, with broadly lanceolate green 

 center. 21. A. arciica. 



Plant elabrous 22. A. laevigata. 



He^s ^ mm. broad, 30-40-flowered ; coroUa glandular-granuUferous; plant glabrous; 

 bracts with hght brown margins. 23. A. Parryu 



VII. FaANSERlOIDES. 



One species. 24. A. franscrioides. 



T.paf-seements again divided or lobed. , 



Inflorescence much branched. pjTamidal; heads very numerous; involucre campanu- 

 late. 4 mm. high, l a-30-flowered ; leaf-segments obovate m outhne. 



Inflorescence narrow, cylindric; heads fewer; involucre hemispheric, 3 mm. high. 25- 

 35-flowered; leaf-kegments lanceolate, short, acute. 26. A. tncompta. 



T pftvps or their segments entire or nearly so. « ^ „ ^ . i i, - 



Heads not very numerous, comparatively large, 25-50-flowered ; mvolucre hemis- 



lufloreJcence spike-like; suffruticose with a woody base; ^^^^^^^^^f^^^^^^^l;?^^- 



Inflorescence open-pamcul? 



TfinVAe lanceolate, thin 



27. A. elatioT. 



