KEY TO THE SPECIES 



12. ARNICA (Arnica) 



Erect perennial herbs with mostly simple stems, opposite leaves, conspicuous 

 long-peduncled heads of yellow flowers and linear pubescent achenes. 



1. Arnica cordifolia Hook (Reart-jmaf Arnica). Somewhat pubescent or 

 villous, 1-3 dm. high ; radical and lower stem leaves cordate- ovate, long-petioled ; 

 stem leaves 1-3 pair, the upper small, ovate or oblong and sessile ; heads broad 

 (4-7 cm.), solitary or additional paired ones from the uppermost axils ; bracts of 

 the involucre ovate to narrowly oblong, acuminate. Moist wooded slopes. 



2. Arnica fulgens Pursh (Shining Arnica). Obscurely pubescent, erect, 

 slender, 1-4 dm. high ; leaves 3-6 pair, erect or ascending, 3-5-nerved, narrowly 

 oblong, sometimes denticulate, tapering into a broad margined base ; heads 

 nearly as large as in the preceding, usually solitary, sometimes a pair from the 

 uppermost axils ; bracts of the involucre oblong. Moist open slopes and plains. 



13. SENECIO (Groundsel. Senecio) 



Herbs with alternate leaves, solitary or clustered heads of yellow flowers, 

 cylindrical simple involucre of erect more or less united scales, and pappus of 

 very numerous soft and slender white hairs. (See Plant BelatioriSt p. 114, 

 Fig. 114.) 



* Leaves entire ; heads few, medium size. 



1. Senecio perplexus Aven Nelson (Early Senbcio). At first loosely floc- 

 cose-wooUy, soon becoming glabrate, stem erect, rather stout, 3.5-5 dm, high ; 

 leaves basal or below the middle (the uppermost being reduced to linear bracts), 

 oblanceolate to oblong, tapering to a short margined petiole, margin sometimes 

 denticulate or crisped ; inflorescence a cymose-corymb of 8-15 heads ; the central 

 peduncles short, often over-topped by the lower ; involucral bracts linear, black- 

 tipped ; rays 5-10 ; achene linear, as long or longer than the fine pappus. Fre- 

 quent ; moist open slopes. 



2. Senecio Purshianus Nutt. (Pursh's Sbnecio). Permanently white-tomen- 

 tose, mostly low and tufted, the several or numerous stems scapose-bracted above, 

 1-2 dm. high ; leaves linear or narrowly oblanceolate ; heads few, with few but 

 conspicuous rays. 



* * Leaves pinnately lobed, toothed or laciniate. 



3. Senecio Flattensis Nutt. (Platte Senecio). Floccose woolly, the stem 

 somewhat permanently so ; stem mostly simple and not tufted, 3-5 dm. high ; 

 basal leaves oblong, on slender petioles, serrate or somewhat lobed at base ; stem- 

 leaves longer, lanceolate or oblanceolate in outline, deeply lobed and the lobes 

 dentate ; heads several or numerous, in a rather open cymose-corymb ; rays con- 

 spicuous. Frequent on Colorado plains. 



4. Senecio Nelsonii Rydb. (Nelson^'s Senecio). Rather thinly tomentose, 

 soon nearly glabrous, very densely tufted ; the numerous stems erect, sparsely 

 leafy, 1.5^ dm. high ; leaves crowded on the crowns, oblong to lanceolate in out- 

 line, sinuately toothed or lobed ; inflorescence a sub-umbellate crowded cyme ; 

 heads 7-10 mm. high ; achenes brown, glabrous and distinctly striate. Gravelly 

 slopes and banks. 



