GENUS CHRYSOTHAMNUS. 

 HISTORY, LIMITS, AND RELATIONSHIPS. 



The genus Chrysothamnus is a member of the Astereae or aster tribe of the Compositae 

 and is closely related to Haplopappus. Within the limits of the genus as here set, there 

 have been described a total of 88 forms, nearly all of which have been given the rank of 

 species at one time or another. These are now organized into 4 sections, 12 species, and 

 40 subspecies. Since it is well known that generic lines are difficult to draw in this group 

 of the Compositae, it is not surprising that the species have been assigned at various times 

 to no fewer than 6 different genera. Although Chrysothamnus was proposed by Nuttall 

 in 1840, it was not until within the last 25 years that there has been an approximate 

 agreement among systematists as to its proper limits. Even at the present day there is 

 a strong tendency to unite the section Punctati of this treatise with Ericameria, a section 

 or subgenus of Haplopappus. On the other hand, however, in only three instances have 

 species of other genera been referred to this one, and there is little doubt that the group as 

 now accepted is a natural one. 



The first species of Chrysothamnus to receive recognition were described by Pursh as 

 members of the South African Chrysocoma (Pursh, Fl. Am. Sept. 2:517, 1814), a genus 

 well separated from the one now under consideration by its nearly globose, solitary heads, 

 the bracts of which are foliaceous and not at all vertically ranked, and by its compressed 

 achenes. This usage was followed by Nuttall four years later in his Genera of North 

 American Plants, where two species are described. In 1834 Hooker (Fl. Bor. Am. 2:24) 

 described a species under the name Crinitaria viscidifiora, but the true Crinitarias are 

 species of Aster and were so accepted by Bentham and Hooker in their Genera Plantarum 

 (2:274, 1873), in which work viscidifiora is referred to Chrysothamnus (p. 256). 



It was in 1836 that DeCandolle established for these plants a name under which they 

 were destined to be known more or less continuously for over half a century. This was 

 Bigelovia (DeCandolle, Prodr. 5:329, 1836), a name which, as Greene has pointed out, 

 had at least five chances to revert because of its having been previously used for other 

 genera, and what is still worse, a name that was made to include species so widely sepa- 

 rated phylogenetically that it can not possibly be retained for all of them. Fortunately 

 for Chrysothamnus, DeCandolle took as the type of his Bigelovia not one of the West 

 American shrubs now under consideration, but the decidedly herbaceous southeastern 

 B. nudata, or Chondrophora nudata as it is sometimes known. The true Bigelovias as 

 represented by nudata, differ from all species of Chrysothamnus not only in their very 

 different habit, but also in a number of other characters, which may be contrasted as 

 follows : 



Bigelovia (Chondrophora). 

 Perennial herbs. 

 Leaves chiefly basal, the few upper ones different in 



shape from the lower. 

 Involucral bracts spirally imbricated, with no tendency 



to form vertical rows. 



Flowers 3 or 4. 



Receptacle with central cusp. 



Corolla-lobes very long, strongly recurved. 



Achenes short, turbinate. 



Style-branch abruptly narrowed to the appendage. 



Chrysothamnus. 

 Shrubs. 

 Leaves equitably distributed, all ahke. 



Involucral bracts imbricated in vertical rows, or at 

 least with an obvious tendency towards a vertical 

 alignment. 



Flowers 5 to 20 (occasionally only 4). 



Receptacle without cusp. 



Corolla-lobes shorter, seldom much recurved. 



Achenes longer, narrower. 



Style branch tapering to the appendage. 



Every attempt should be made to conserve genera and generic limits after they have 

 been in use for long periods of time. It would therefore seem desirable to use Bigelovia 

 in a sense so inclusive as to embrace both of the above groups. This, however, would 



