[Vol. 2 



592 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Sect. 2. Eremophili Greenm. 



2. Eremophili Greenm. Monogr. Senecio, I. Teil, 21, 23. 

 1901, and in Engl. Bot. Jahrb. 32 : 17, 19. 1902. 



Annual or biennial herbs, not infrequently becoming peren- 

 nial by the development of a ligneous base ; stems leafy; leaves 

 laciniately pinnatifid ; inflorescence a terminal corymbose or 

 paniculate cyme; heads radiate, rays conspicuous; achenes 

 glabrous or pubescent. Sp. 8-13. 



Key to the Species 



A. Plants glabrous; achenes smooth or slightly hirtellous. 



a. Heads 7 to 10 mm. high; involucral bracts 5 to 



7 mm. long, usually conspicuously black-tipped, 

 a. Involucre 3 to 5 mm. in diameter, 20-35- 



flowered 8. 8. MacDougalii 



p. Involucre 5 to (i mm. in diameter, 35-50- 



flowered 9. 8. ambrosioidcs 



b. Heads 10 to 12 mm. high; involucral bracts 7 to 



10 mm. long, not conspicuously black-tipped. 



a. Northern species (Canada and the U. S. ) 10. 8. eremophUus 



/9. Southern species (Mexico) 11. 8. Towntendii 



B. Plants more or less tomentosc; achenes canescent- 



pubescent. 



a. Leaves at first tomentulose, later glabrate 12. 8. chihuahuensia 



b. Leaves permanently tomentulose tS. 8. durangensis 



8. S. MacDougalii Heller, Bull. Torr. Bot. Club 26 : 592. 

 1 899 ; Oreenm. Monogr. Senecio, I. Teil, 23. 1901, and in Engl. 

 Bot. Jahrb. 32 : 19. 1902, in part ; Eydb. in Fl. Colo. 397. 1906, 

 in part; Wooton & Standley, Contr. U. S. Nat. Herb. 19 : 745. 



1915. 



8. eremophUus Gray, Syn. Fl. N. Am. I 2 : 392. 1884, and 

 ed. 2, 1886, in part, not Richards. 



S. eremophUus var. attenuatus Greenm. Monogr. Senecio, 

 I. Teil, 23. 1901, and in Engl. Bot. Jahrb. 32 : 19. 1902. 



Glabrous throughout or slightly puberulent above; stem 

 simple or branched, 5 to 8 dm. high, leafy to the inflorescence ; 

 leaves more or less laciniately pinnatifid, 3 to 10 cm. long, 1.5 

 to 5 cm. broad, segments linear to lanceolate, entire to coarsely 

 and unequally dentate ; inflorescence terminating the stem and 

 branches in corymbose cymes; heads 7 to 10 mm. high, radi- 

 ate; involucre narrowly campanulate, calyculate, 3 to 5 mm. 

 in diameter; bracts of the involucre usually 13 (8-13), linear- 



