494 



COMPOSITAE (COMPOSITE FAMILY) 



bescence softly silky-canescent throughout : leaves spatulate-oblong or oblong 

 and sessile: heads few to many, corymbose; bracts of the villous-canescent 

 involucre narrowly linear-lanceolate: outer pappus minute. Plains of the 

 upper Platte. 



9. CHRYSOTHAMNUS Nutt. RABBIT BRUSH. 



GOLDENROD 



RAYLESS OR FALSE 



Shrubby or suffrutescent plants with narrow or terete entire leaves. Her- 

 bage white-tomentose or glabrous, often viscidulous or resinous. Inflores- 

 cence paniculate, cymose, or rarely racemose. Heads homogamous. In- 

 volucre narrow; the bracts well imbricated usually in more or less distinct 

 vertical ranks, chartaceous or coriaceous, mostly destitute of herbaceous tips. 

 Ray-flowers uniformly wanting; disk-flowers 5-30. Style-branches subulate 

 or filiform, usually long-exserted. Achenes narrow, terete or slightly angled, 

 pubescent. Pappus copious, soft, commonly dull white. Bigelovia. 



The entire plant wholly devoid of tomentum. 



Tall (5-10 dm.); branchlets slender-virgate or stouter and fas- 



tigiate; leaves scabrous-margined. 

 Growing on the wet banks of alkali creeks (strikingly halophy- 



tic) l.C. linifolius. 



Growing on dry hills, in .soil free from alkali . . . 2. C. glaucus. 



Low (5 dm. or less); usually freely branched. 



Leaves glabrous but sometimes scabrous on the margins. 



Leaves 3-nerved, often involute and twisted . . . 3. C. pumilus. 



Leaves 1-nerved, flat, ciliate on the margin . . 4. C. Greenei. 



Leaves puberulent or scabrous, but often very minutely or 



sparingly so. 

 Bracts not acuminate, but often subacute. 



Achenes pubescent 5. C. lanceolatus. 



Achenes glabrous . . . . . . . 6. C. Vaseyi. 



Bracts firm and sharply acuminate . . . . . 7. C. depressus. 



Tomentose, in some species densely so and in the others at least traces 



upon stems or leaves. 

 Branchlets permanently white-tomentose. 



Plant widely bushy-branched 8. C. graveolens. 



Plant strict with erect branches . . . . . . 9. C. nauseosus. 



Branchlets either glabrate from the first or shedding more or less 



of their tomentum. 



Involucral bracts acuminate or at least sharply acute, arachnoid- 

 ciliate. 



Achenes glabrous 10. C. Bigelovii. 



Achenes pubescent. 



Leaves linear, 1-nerved (in no. 12 sometimes surpassing 



the flowers). 

 Involucral bracts long-acuminate, somewhat divaricate, 



the upper usually exceeding the corolla. 

 Flowers yellow; bracts arachnoid-ciliate on the mar- 

 gins; leaves green, not surpassing the flowers . 11. C. affinis. 

 Flowers pale or dirty yellow; bracts lanate; leaves 

 pale or yellowish-green, the upper often longer 

 than the flowers . . . . . 12. C. Howardii. 



Involucral bracts merely acute, erect, shorter than the 

 corolla, arachnoid-ciliate; leaves canaliculate, 3-6 

 cm. long ........ 13. C. wyomingensis. 



Leaves broadly linear, 3-nerved, green, the upper surpass- 

 ing the flowers 14. C. Parryi. 



Involucral bracts not acuminate, lanceolate and acute or nar- 

 rowly oblong and blunt. 



Bracts quite glabrous, not glutinous; leaves glabrous at ma- 

 turity; stems slender, erect, 4-6 dm. high . . 15. C. oreophilus. 

 Bracts erose-ciliate on the margin, or tomentose, or both, and 

 sometimes glutinous; some tomentum persisting on the 

 leaves. 

 Plant 5-12 dm. high, with branched trunk-like base, the 



season's stems slender-virgate, erect .... 16. C. pulcherrimus. 

 Plant 2-5 dm. high, freely branched from the base. 



Leaves almost filiform and widely divaricate . . 17. C. plattensis. 

 Leaves linear, mostly erect ...... 18. C. frigidus. 



1. Chrysothamnus linifolius Greene, Pitt. 3: 24. 1896. Tufted, woody 

 stems erect, slender and flexible, 6-10 dm. high, fastigiately brandling above, 



