54 GENUS ARTEMISIA. 



are there absent. The extreme development of the white form, with the leaves nearly all reduced to the trifid 

 type and with numerous gray, brittle twigs, is found at the most easterly known station for the species, namely 

 7 km. southeast from Palm Springs (February 1921, Jaeger). AU of these characters are in line with the general 

 tendency in desert vegetation. The ternately cleft nature of the foliage is derived from the pinnate type, as 

 indicated by specimens in which the leaves are 3-Iobed, but with one lobe attached lower down than the others 

 (130825 UC); in the typical form some of the leaves are often only ternately cleft or bifid at the summit (29665 

 UC and 91195 UC), while others are irregularly pinnatifid. Some of these leaf-forms are shown on the accom- 

 panying plate. The type offoliosa came from around Monterey. 



5. Crossostephium californicum Rydberg, N. Am. Fl. 34 : 243, 1916. A. californica. 



6. C. FOLiosuM Rydberg, 1. c. A. californica, the form, or state, referred to under No. 4. 



7. C. INSULARE Rydberg, 1. c. 244. A robust, insular variation of A. californica with leaf-segments 1 to 

 3 mm. wide and not revolut«. Thus far it is known only from San Clemente and San Nicholas Islands, off the 

 coast of southern California. The typical form also grows on at least one of these (San Clemente Island, 

 March 25, 1918, Evermann, Calif. Acad. Sci.). On neighboring islands are found forms intermediate between 

 the type of californica and the one listed above as folinsa. The remarkable width of the leaf-segments and 

 rachis in insulare is the result of the failure of the margins to become closely revolute, as in the other varia- 

 tions. This condition is approached in specimens from near Santa Monica, on the mainland nearly opposite 

 the islands on which insulare grows. In these the leaf-margins are revolute but do not meet. The largest 

 leaf -segments are 1.5 mm. wide (near Santa Monica Experiment Station, Barber 284, UC). Segments up to 1.8 

 mm. wide occur on vigorous shoots from as far north as the Oakland HOIs. Two color-forms occur on the 

 islands, both with the wide leaf-lobes, so that il foliosa is accepted as a species, or variety, it will be necessary 

 similarly to recognize these forms. The type of insulare came from along Pot's Trail, San Clemente Island. 



RELATIONSHIPS. 



There has been a wide divergence of opinion as to the relationships of this species. 

 Both Gray and Rydberg have assumed a close connection with Crossostephium artemi- 

 sioides Lessing (Artemisia chinensis Vahl, not Linnaeus), a species of the Philippine 

 Islands and China. The former author would therefore unite the genus Crossostephium 

 with Artemisia (Syn. Fl. N. Am. P:370, 1884), while Rydberg would refer californica, 

 together with 2 minor segregates, to the genus Crossostephium (N. Am. Fl. 34:243, 

 1916). The bases for this assumed relationship were (1) a distinct ribbing of the disk- 

 achenes and (2) the supposed presence of a coroniform pappus, two characters not other- 

 wise known at that time in the genus, except in the Hawaiian J., australis Lessing. There 

 can be no question as to the ribbing of the achenes in A. californica. In mature fruits 

 these ribs take the form of 5 sharp angles ; 3 and 4 ribs are included in descriptions but a 

 careful examination of numerous collections indicates that 5 is perhaps the universal 

 number. The presence of these angles suggests a remote connection, through forms 

 now extinct, with true Crossostephium of southeastern Asia, but further evidence is 

 needed in support of the hypothesis. This evidence is not to be found in the presence 

 of a pappus or in any other character thus far pointed out. As a result of detailed 

 studies on a large series of specimens, the conclusion is reached that the Californian 

 species never shows any evidence of a true pappus. The summit of the achene is broad 

 and the edges commonly curve upward to form a shallow cup or rim about the base of 

 the corolla-tube, as indicated in the detailed drawings of plate 2. But there is no reason 

 to interpret this as a pappus-crown, and, in fact, it is no more prominent than in some 

 species universally accepted as genuine Artemisias, for example, A. pontica and A. 

 tridentata (plates 1 and 18). There is never any splitting of this rim nor the presence 

 of distinct paleae as in the case of true Crossostephium. Furthermore, this monotypic 

 genus differs decidedly from our American plants in the presence of 2 rows of ray-flowers, 

 a character apparently overlooked both by Gray and by Rydberg. Although A. cali- 

 fornica and A. australis were described by Lessing in the same volume as his genus 

 Crossostephium, he made no comparisons with this last and presumably had no thought 

 of their relationship. His treatment, which considers Crossostephium as a monotypic 

 genus and refers californica and australis to Artemisia, was followed by Bentham and 

 Hooker and by Hoffman in Engler and Prantl's Pflanzenfamilien and is the one which 



