62 GENUS ARTEMISIA. 



The relationship of each of these to norvegica will be discussed under the respective 

 species. The exact place of origin of norvegica probably will never be determined, but 

 from the facts of distribution it seems to have been somewhere near the central portion 

 of Eurasia. After its migration toward the north, the species spread west and east 

 along the Arctic shores and seems to have broken up into two principal stocks, one 

 resulting in the form represented by the present nomenclatorial type, the other yielding 

 a group of forms centering around subspecies saxatilis. The former is of northwestern 

 distribution, being most abundant in Scandinavia; the latter belongs to extreme north- 

 eastern Asia and America. No specimens are at hand from the intervening area, that 

 is, northern Siberia, and it seems from the literature that no forms of the species are 



Inflorescence open. Inflorescence close, 



paniculate or loosely narrowly racennose fo 



racemose ; large glomerulate ; low plants, 



plants, mostly green mostly canescent or silky 



Fio. 6. — Phylogenetic chart of the subspecies of Artemisia norvegica. 



there present. If further exploration proves this to be the case, then the close similarity 

 between Scandinavian and American forms will be most remarkable. It is quite possible, 

 however, that the species has reached America through a route extending westerly 

 from Scandinavia, since Wille reports it in Greenland (Engler's Bot. Jahrb. 36, beiblatt 

 81 :58, 1905). The Old World and Rocky Mountain types are so nearly alike in most of 

 their characters that W. J. Hooker was unable to see any differences whatever between 

 certain specimens from Norway and others from the Rocky Mountains (Hooker, Fl. 

 Bor. Am. 1:325, 1833). But a careful comparison of large series from both regions 

 establishes certain decided tendencies which render their subspecific separation highly 

 desirable, while at the same time the overlapping in all essentials makes their specific 

 segregation impossible. Typical norvegica, as it grows in Scandinavia, is a plant with 

 leaf-blades often as broad as long through the congestion of the segments near the end 

 of the rachis; the heads average larger than in any American variety (see table 4), and 

 the peduncles are usually longer. In all of these characters, however, it is sometimes 

 matched by forms of subspecies saxatilis. Although the two are widely separated 

 geographically, there are some specimens of each that can not be positively identified 



