176 GENUS CHRYSOTHAMNUS. 



Stephens; California: Chuckawalla Bench, Colorado Desert, Schellenger 19 (UC); 

 between Cabezon and Whitewater, Parish 651 (Gr, UC, US) ; near Bagdad, southern 

 Mojave Desert, May 20, 1902, Brandegee (UC); eastern slopes of Tehachapi Pass, Hall 

 10961 (UC); Resting Springs Valley, Inyo County, Cotnlle and Funston 280 (US). 



SYNONYMS. 



1. BiGELOViA PANicuLATA Gray, Proc. Am. Acad. 8 : 644, 1873. The first publication with a description of C 

 paniadatus. 



2. Ericameria PANICULATA Rydberg, Fl. Rocky Mts. 853, 1917. Based upon Bigelovia paniculata. 



3. LiNOSYRis (Chrysothamnus) viscidiflora var. PAmcuiATA Gray, Hot. Mex. Bound. 80, 1859. This 

 was the first publication of the name, but it was not accompanied by a description. 



RELATIONSHIPS. 



Because of its similarity to species of Haplopappus section Ericameria, especially in 

 the resinous-punctate herbage, this is taken as one of the most primitive of the Chryso- 

 thamni, and hence it stands first in the taxonomic sequence. It differs from all species 

 of Haplopappus in the vertical arrangement of the involucral bracts and in the narrow 

 heads, while from the species which are most like it in other respects it differs also in the 

 absence of ray-flowers. Its habitat in the southwestern deserts, where it borders upon 

 the areas inhabited by species of Ericameria, also argues for its former connection with 

 that group. The characters of C paniculatus are remarkably constant, at least as far 

 as indicated by the specimens at hand. The length of corolla varies by only 0.2 mm., 

 or less than 5 per cent, as contrasted with variations of 3 to 6 mm., or about 100 per 

 cent in some of the more plastic species (table 17). In relative length of style-appendage 

 and stigmatic portion, however, the variation is nearly as great as in the most variable 

 species, namely, C. nauseosus. In most other floral characters and in vegetative features 

 the plants show but little fluctuation. In Brandegee's specimens from Bagdad, cited 

 above, the inflorescence is very narrow, almost racemose in fact, but aside from this 

 collection there are no variations of consequence and there have been no attempts to 

 segregate the species into varieties or other divisions. This remarkable uniformity is no 

 doubt due in part to the restricted distribution of C. paniculatus and suggests that this 

 species is much more primitive than the more plastic, variable and aggressive ones at 

 the opposite end of the genus. 



ECOLOGY AND USES. 



Chrysothamnus paniculatus is a rare species of little ecological significance. In life- 

 form it is a bush, flowering from May to October. It is subclimax in position, occurring in 

 rocky streamways with Lepidospartum squamatum, Hymenoclea salsola, and Encelia 

 frutescens, or with one or more of them, usually in the Larrea-Yucca ecotone. 



It seems unlikely that commercial products will ever be obtained from this plant. 

 The scarcity of the supply would alone prevent the utilization of the wild shrubs. It is 

 possible, however, that through selection, and especially through cross-breeding with 

 C. teretifolius, a rubber plant might be discovered with sufficient promise to warrant cul- 

 tivation on a commercial scale. The rubber-content of wild plants has been found to 

 average only about 2.5 per cent, but there is reason to believe that strains or at least 

 individuals can be found that will run much higher than this. The large size of the 

 shrubs, their resistance to low temperatures, and their ability to grow in the poorest of 

 soil where the water content is exceedingly low, are all characteristics highly desirable 

 in rubber plants. The nature of the product will be taken up under the next species. 



2. CHRYSOTHAMNUS TERETIFOLIUS (Durand and Hilgard) Hall, Univ. Calif. 

 Publ. Bot. 3:57, 1907. Plate 24. 



Shrub 3 to 9 dm. or rarely even 20 dm. high, irregularly much branched and spreading 

 to form a flattish or rounded bushy plant; bark of main stems dark gray, more or less 



