1919] Hall: Chrysothamnus )wuseosus and Its Varieties 179 



21. Chrysothamnus nauseosus var. mohavensis (Greene) comb. iiov. 



Bigeloviu mvliavensis Greene, in Gray, Syn. Fl., vol. 1, part 2, p. 138, 1884. 

 Clniisnthavinns mohavensis Greene, Eryth., vol. 3, p. 113, 1895. 



Shrub of medium or large size, with many erect or ascending 

 branches which are often nearly leafless and rush-like: leaves filiform, 

 very acute, 1-nerved, nearly glabrous : inflorescence a rounded or some- 

 what elongated thyrse : involucre narrow, 9 to 10 mm. long, sharply 

 5-angled; bracts obtuse to acute, in very distinct vertical ranks, 

 glabrous: corolla 8 to 10 mm. long; lobes 1.5 to 1.8 mm. long, spread 

 ing. 



In this variety we have apparently a southern derivative of viridu- 

 lus. It belongs to higher ground where the drainage is better and the 

 soil not obviously alkaline. It skirts the westerly side of Owens Valley, 

 California, extending southward to the slopes west of Antelope Valley 

 and swings around the latter as far as the desert slopes of the San 

 Bernardino Mountains. It occurs also at an isolated station on 

 Mt. Hamilton, far out of its general known range, but the specimens 

 at that station seem entirely typical and Dr. Greene, the first to detect 

 the form, himself admitted them as mohavensis. The species will 

 probably be found elsewhere along the hot inner South Coast ranges, 

 a little-explored district where many species of the soutlicrii deserts 

 extend their ranges northward. 



Although first described as sparsely leafy or leafless this character 

 cannot be relied upon since the tendency toward an early dropping 

 of the leaves is common to the whole group. It is true, liowever, that 

 mohavensis is more commonly leafless or nearly so. Tlie naked wand- 

 like branches are sometimes much elongated, in one case measuring 

 7.5 dm. without leaf or branch (11. M. H., no. 10570). The best 

 characters lie in the involucre, which is mostly longer than in the 

 other forms. Although the longest involucres of virididus slightly 

 exceed the shortest ones of mohavensis, yet tlie average of the former 

 is about 7 mm., of the latter about 9 mm. The l)racts are distinctly 

 five-ranked and carinate, so that the involucre is sharply five-angled. 

 They are somewhat obtuse but in some specimens which are referable 

 here by all other characters the bracts are decidedly acute (II. M. H., 

 nos. 9894, 10570, 10611, and Hall and Babcock, no. 5090). 



As indicative of the gradation between mohavensis and viridulus 

 may be cited a specimen from Oak Creek, along the west side of 

 Owens Valley (H. M. H., no. 10611). The habit is that of mohavensis 

 althouuh some of the twigs were leafy when gathered on October 30. 



