CARDUACEAE. 343 



21. Chrysothamnus serrulatus (Torn) Rydb. {Bigelovia Douglasii ser- 

 rulata A. Gray; C. glaucus A. Nels.) On dry plains of Wyo. and Utah to 

 Colo. — Alt. 5000-8000 ft. — Gypsum ; road to Steamboat Springs ; Cottonwood 

 Lake; South Park, near Jefferson; North Park; headwaters of Clear Creek; 

 Twin Lakes; Middle Park. 



22. Chrysothamnus latifolius (D. C. Eaton) Rydb. (Bigelovia Douglasii 

 latifolia A. Gray) On dry plains from Mont, and Wash, to Colo. 



23. Chrysothamnus lanceolatus Nutt. {Bigelovia Douglasii lanceolata A. 

 Gray) On dry plains and hills from Mont, and Wash, to Colo. — Alt. 7000- 

 8500 ft. — Cottonwood Lake ; Grizzly Creek ; Black Canon ; Cerro Summit ; 

 North Park, near Walden ; Hayden, Routt Co. 



24. Chrysothamnus puberulus (D. C. Eaton) Greene. (Linosyris viscidi- 

 Hora puberula D. C. Eaton) On dry plains and hills from Mont, and Wash, 

 to Colo, and Utah. — Alt. 8000-9500 ft. — Pitkin ; Parlin ; South Park, south- 

 east of Jefferson. 



25. Chrysothamnus Vaseyi (A. Gray) Greene. (Bigelovia Vaseyi A. Gray) 

 In the mountains of Wyo., Colo, and Utah. — Alt. about 7500 ft. — Middle 

 Park; Greene, North Park; Gunnison; Squaw Hill, above Cimarron. 



10. ISOCOMA Nutt. 



Bracts acute, linear-lanceolate. i. /. phiriiiora. 



Bracts obtuse or obtusish, linear, oblong or oblanceolate. 2. /. Wrightii. 



1. Isocoma pluriflora (T. & G.) Greene. (Bigelovia pluriflora A. Gray) 

 On plains of Colo. — " On the Arkansas." 



2. Isocoma Wrightii (A. Gray) Rydb. (Bigelovia Wrightii A. Gray) On 

 banks and in saline soil from Colo, to Tex. and Ariz. — Alt. 4000-5000 ft. — 

 San Juan Valley (Brandegee). 



II. SIDERANTHUS Nutt. 



Leaves spinescently toothed, not pinnatifid. 



Heads discoid; perennial with woody caudex. i. S. grindelioides. 



Heads radiate ; annual. 2. .S". annuus. 

 Leaves pinnatifid at least the lower ones. 



Stem more or less floccose or cinereous, especially when young. 



Plant cinereous-pubescent, more or less glandular. 3. S. australis. 



Plant more or less floccose, not at all glandular. 4. S. spinulosus. 

 Plant neither floccose nor cinereous. 



Plant glabrous or slightly glandular-puberulent. 5. 6". glaberrimiis. 

 Plant decidedly pubescent. 



Plant finely puberulent. 6. 6". puberulus. 



Plant hispid-strigose. 7. 5". gracilis. 



1. Sideranthus grindelioides (Nutt.) Britton. (Aplopappus Nuttallii T. 

 & G.) On dry plains and hills from Ass. and Nev. to Neb. and Ariz. — Alt. 

 4000-5500 ft.^Grand Jimction; Rifle; Hotchkiss. 



2. Sideranthus annuus Rydb. (Aplopappus rubiginosus A. Gray; not T. 

 & G.) On sandy soil from Neb. and Colo, to Kans. and Tex. — Alt. 4000- 

 5000 ft. — Platte Valley, Julesburg; New Windsor; Ft. Collins. 



3. Sideranthus australis (Greene) Rydb. (Aplopappus australis Greene) 

 On dry soil from Colo, to Tex. and N. M. ; also in Mex. — Alt. about 4700 ft. 

 — Deer Run. 



