730 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Attempts have been made to obtain rubber from this and allied species, in southern 

 Colorado. It is possible to secure rubber from this source, but the quantity of the 

 plant available does not seem sufficient to warrant an elaborate equipment for its 

 extraction. 



115. RYDBERGIA Greene. 



Stout, low, sparingly branched, woolly, alpine perennial with pinnately parted, 

 mostly basal leaves and large heads with spreading, bright yellow rays; bracts of the 

 involucre all alike, distinct, herbaceous, in several series, woolly; receptacle large, 

 hemispheric; rays 15 to 30, linear-cuneiform; paleae of the pappus 5 or 6, elongated- 

 lanceolate, attenuate to a subulate point. 



1. Rydbergia brandegei (Porter) Rydb. Bull. Torrey Club 33: 156. 1906. 



Actinella grandiflora glabrata Porter in Port. & Coult. Syn. Fl. Colo. 76. 1874. 



Actinella brandegei Porter; A. Gray, Proc. Amer. Acad. 13: 373. 1878. 



Type locality: Sangre de Cristo Pass, Colorado. 



Range: Southern Colorado to New Mexico. 



New Mexico: Taos Mountains; Baldy; Santa Fe and Las Vegas mountains; White 

 Mountain Peak. High mountain peaks, in the Arctic-Alpine Zone. 



116. TETRANEURIS Greene. 



Usually scapose, annual or perennial herbs with mostly basal, entire, often punctate 

 leaves and long-pedunculate heads; disk flowers and rays bright yellow; involucre 

 hemispheric, of 2 or 3 series of similar appressed imbricated bracts; receptacle convex 

 or conic, naked; achenes turbinate, 5 to 10-ribbed or angled, variously pubescent; 

 pappus of 5 to 12 scarious, aristate, truncate or acuminate paleae. 



key to the species. 



Annual; stems much branched 1. T. linearifolia. 



Perennials; stems simple or nearly so. 



Flowering stems bearing 2 to 4 leaves, sometimes with 1 or 2 

 branches. 

 Paleae of pappus long-arista te. 



Leaves and stem densely sericeous; heads 12 mm. in 



diameter or less 2. T. argentea. 



Leaves and stems glabrate; heads about 15 mm. 



broad 3. T. ivesiana. 



Palese of pappus broader, abruptly acuminate, never 

 aristate-tipped. 



Involucres 7 mm. high; rays 15 mm. long 4. T. formosa. 



Involucres 5 mm. high; rays 10 mm. long or less 5. T. leptoclada. 



Flowering stems naked, simple. 



Plants less than 10 cm. high; heads little or not at all 

 exceeding the leaves. 

 Leaves 5 cm. long or less, nearly linear, 3-nerved at 



the base 6. T. trinervata. 



Leaves less than 3 cm. long, oblanceolate, not 3- 

 nerved at the base. 

 Leaves loosely villous; heads 12 to 13 mm. 



broad; rays equaling the involucre 7. T. depressa. 



Leaves densely sericeous; heads less than 10 mm. 



broad; rays shorter than the involucre S. T. pygmaea. 



Plants more than 10 cm. high; heads much exceeding the 

 leaves. 

 Leaves densely sericeous 9. T. acaulis. 



