156 



GENUS ARTEMISIA. 



be accounted for in this way. As far as examined, each bract subtends one of the disk- 

 flowers. When the latter are numerous, some of them are devoid of bracts. It therefore 

 seems more reasonable to look upon the presence of receptacular bracts as a case of 

 reversion. This is not due to the persistence of an ancestral trait, as is evident from the 

 high position of Seriphidium within the genus and from the absence of these structures 

 in immediately related genera many of which are more primitive than Artemisia. 



Since no one of the American Seriphidia approaches A. palmeri, its relationships are 

 perhaps to be sought in the Old World, and this must be left for later studies. A possible 

 alternative is its evolution from some group of the section Abrotanum. The habit, cut 

 of leaf, and other features are very suggestive of A. vulgaris mexicana, but a derivation 

 from this group would involve at once the loss of ray-flowers, the development of recep- 

 tacular bracts, and a change in the shape of the achenes in addition to minor changes. 

 This connection is therefore scarcely more than a remote possibility. 



As compared with most Artemisias, the achene more closely approaches a truly pris- 

 matic shape. It is even more decidedly quadrangular and evenly truncate at summit 

 than in other species of the section Seriphidium, where subprismatic achenes are the rule. 

 Although sharply 4-angled, the achene is not otherwise ribbed or crowned, as sometimes 

 described. The characters of the corolla, even down to the peculiar glandular-granu- 

 liferous tube and the style-branches, are as in other members of its section. Other char- 

 acters are indicated in the subjoined table. 



ECOLOGY AND USES. 



Artemisia palmeri is a tall shrub with more or less herbaceous branches. It forms a 

 sparse consocies in ravines and along moist banks, and also pushes a short distance up 

 slopes, where it meets A. calif ornica and its associates. 



It is rare and local, and hence has not been used, though its odor suggests that it may 

 possess the value of certain European species for flavoring. 



Table 16. — Variation in Artemisia palmeri. 



No. of 

 bracts of 

 receptacle. 



No. of 

 flowers. 



Length 

 of disk- 

 corolla. 



San Diego County, Calif, (type) . 



Near San Diego, Calif 



National City, Calif 



La JoUa, Calif 



Alpine, Calif 



All Saints Bay, Lower Calif 



Gr 



29705 UC 

 91220 UC 



Gr 

 239844 US 



Gr 



Average . 



2.0 2.5 

 3.5 



25 30 

 2.0 



2.1 2.5 

 2.0 3.0 



2.5 



9 



10 10 



10 9 



11 



