32 



GENUS ARTEMISIA. 



Although a discussion of Tanacetum and its three segregates does not fall within the 

 province of this paper, Chamartemisia is so near Artemisia that its generic position should 

 be here considered. This proposed segregate of Tanacetum has the subulate anther-tips 

 of Artemisia, but in habit, inflorescence, receptacle, and corollas it agrees with the 

 Sphaeromeria section of Tanacetum. There is, to be sure, no other Sphaeromeria with a 

 pappus, but the genuine species of Tanacetum have a coroniform pappus. The species 

 of Artemisia are universally devoid of pappus, and moreover, the presence or absence of 

 pappus can not be accepted as of generic value in this case. It seems, therefore, that 

 Chamartemisia is much more closely related to Tanacetum than it is to this genus, and 

 that it may be referred to Tanacetum, section Sphaeromeria, or a new section established 

 for it, since its distinguishing characters are not sufficient to sustain a new genus. The 

 inflorescence in the few specimens thus far collected is so reduced that one can not say 

 with certainty whether it is of the paniculate or of the cymose type, but the assemblage 

 of other characters perhaps warrants the conclusion that it is the former. 



Crossostephium, as here delimited, consists of but a single species, namely C. arte- 

 misioides Lessing, based upon Artemisia chinensis Vahl, not Linnaeus, a species of the 

 Philippine Islands and China. Gray had suggested that this be reduced to Artemisia 

 and that it stand next to A. australis Lessing, of the Hawaiian Islands, and A. calif ornica 

 Lessing, of western North America (Syn. Fl. P : 370, 1884). Rydberg has taken the 

 same view of this relationship, but refers all three of the species just mentioned to the 

 genus Crossostephium. It seems that both treatments are erroneous, and that it is better 

 to restrict Crossostephium to C. arteviisioides alone. This belief is based upon a careful 

 examination of material, by which it is found that the American and Hawaiian species 

 referred to Crossostephium are lacking in the two essential features of that genus, namely, 

 the coroniform pappus and the double row of ray-flowers. A more detailed statement 

 is given in the discussion of the relationships of A. calif ornica (p. 54). 



The two remaining segregates of Artemisia indicated in the preceding key are based 

 each upon a single character. Picrothamnus, with but one species, A. spinescens, 

 is an Artemisia of the section Dracunculus. It was established by Nuttall (Trans. Am. 



' Differs from all the others in the somewhat utricular achenes, the surface of which becomes gelatinous in water. 



' Chamartemisia has pappus of Tanacetum, corolla of Sphaeromeria, and anther-tips of some Artemisias. 



' Crossostephium as originally described has only one species; extended by Rydberg to include Artemisia californiea with 

 ray-flowers in a single row and no pappus (see page 54). 



* Picrothamnus was separated from Artemisia on spiny habit, villous achenes, and villous corollas (achenes and corollas 

 glabrous to rarely pubescent in Artemisia). 



