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; palew of the pappus 5 or 6, elongated- 
lanceolate, attenuate to a subulate point. 
1. Rydbergia brandegei (Porter) Rydb. Bull. Torrey Club 83: 156. 1906. 
Actinella grandiflora glabrata Porter in Port. & Coult. Syn. Fl. Colo. 76. 1874. 
Actinella brandegei Porter; A. Gray, Proc. Amer. Acad. 18: 373. 1878. 
TYPE LOCALITY: Sangre de Cristo Pass, Colorado. 
RanaeE: 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 pales, 
KEY TO THE SPECIES. 
Annual; stems much branched........................2-.-2-2.2. 1. T. linearifolia. 
Perennials; stems simple or nearly so. 
Flowering stems bearing 2 to 4 leaves, sometimes with 1 or 2 
branches. 
Palee of pappus long-aristate. 
Leaves and stem densely sericeous; heads 12 mm. in 
diameter or less..............022-2-000eeeeeee 2. T. argentea, 
Leaves and stems glabrate; heads about 15 mm. 
broad. 2... 2. ee eee eee eee eee 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. 7’. 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... 22.22... eee eee eee eee 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.... 8. 7. pygmaea. 
Plants more than 10 cm. high; heads much exceeding the 
leaves. 
Leaves densely sericeous.................22222-0-00- 9. T. acaulis. 
