Arctic Plants: Geographical Distribution 105 b 



But of these D. octopetala is very rare on the islands of the American archi- 

 pelago (Boothia Felix), and on the west coast of Greenland it has only been 

 found at a very few stations between 76° and 79° N. L., while it is frequent on 

 the east coast between 70° and 76° N. L. D. integrifolia, on the other hand, is very 

 common on the west coast of Greenland, between 60° and 76° N. L., while it has 

 only been found at a few stations on the east coast, between about 70° and 74° 

 N. L. (Dus6n and Hartz) ; from the islands of the archipelago it has been recorded 

 from many stations. 



On the shore between Point Barrow and Bathurst inlet D. octopetala was 

 found only near Sadlerochit river, Alaska; by the GjQa expedition it was found 

 at King point, together with D. integrifolia and the forma intermedia Nathorst. 

 D. integrifolia was, on the other hand, collected at many stations along the 

 entire coast explored by the expedition; the intermediate form was found at 

 Port Epworth harbour. 



Farther westward, at Port Clarence, D. integrifolia was observed by Kjell- 

 man to be quite frequent, while the other species seemed to be absent; but on 

 the Asiatic coast of Bering strait Kjellman found both species, and D. octopetala 

 was very abundant, the other species very rare. Finally, on the north Siberian 

 coast from 173° 24' W. L. to 68° E. L. D. octopetala is the only species, so far 

 observed, according to Kjellman (Sibir. Nord-Kust. Flora I.e.). 



With regard to the third species, D. Drummondii, the distribution of this 

 is on this continent confined to the Canadian provinces. In his Catalogue of 

 Canadian Plants (I.e.), John Macoun states that it never grows on mountain 

 slopes, and that it is distributed from Quebec westward to British Columbia, 

 and extends as far north as the shores of the Arctic sea, according to Richardson. 

 Moreover, it occxu-s in eastern Siberia, along the Aldan river (Turczaniliow). 

 With regard to the Siberian plant Ledebour (Fl. Ross. I.e. Vol. 2, p. 21 ) makes 

 the following statement: "Specimina fructifera, quae benevolentiae cl. Turcz. 

 debeo, ab americanis a cl. Hooker mecum communicatis non differunt nisi 

 laciniis calycinis paulo angustioribus et longioribus." 



We have thus in the genus Dryas three species, the only ones of the genus, 

 viz. : D. octopetala which is circumpolar-alpine, D. integrifolia which is arctic- 

 alpine, and finally D. Drummondii which is only exceptionally arctic, and which 

 furthermore does not seem to be alpine farther south. 



The centre of distribution of D. octopetala and D. integrifolia may have 

 been within the polar regions, from where they migrated towards the south 

 during the glacial epoch. Of these the former became thus widely distributed 

 in the mountains of both Worlds, except the Himalayas, while D. integrifolia did 

 not extend beyond the mountains of this continent. D. Drunimondii, on the 

 other hand, evidently had its centre south of the arctic regions, in the Canadian 

 Rockies evidently, and may have developed much later than the others. D. 

 octopetala and D. integrifolia, especially the former, are still, as we know, repre- 

 sented on the higher mountains as remnants of a glacial flora. The limited occur- 

 rence in the arctic region shown by D. integrifolia well corresponds with its 

 present distribution farther south on the American continent, but, as mentioned 

 above, this species and D. Drummondii have extended their range in a western 

 direction to the eastern part of northern Asia. But with regard to D. octopetala, 

 ■ the wide range which it occupies throughout the mountainous districts of both 

 Worlds is seemingly in good accordance with a former, equally extensive dis- 

 tribution in the polar regions. 



Another interesting distribution may be illustrated by the genus Sieversia, 

 and although only one species, S. glacialis, was found by the expedition, it may 

 be appropriate to give a general view of the distribution of the genus "in toto." 



The following species occur on this continent: S. glacialis R. Br., S. trijlora 

 R. Br., S. Rossii R. Br., S. calthifolia Menz., and S. radiata (Michx.) Greene. 

 Of these, S. triflora is not arctic, but extends from Labrador and Newfoundland 

 to British Columbia, and follows the Rocky mountains south to Colorado 



