102 B Canadian Arctic Expedition, 1913-18 



generally distributed south of the arctic region; moreover, the number of species 

 that occur in Greenland and on this continent only is extremely small : Lesquer- 

 ella, Draba aurea, Hesperis, Arabis Holboellii, and A. Hookeri. 



By comparing the geographical distribution of the genus Saxifraga, we have 

 seen that not less than 7 out of the 15 species collected are circumpolar; and 

 with the only exception of (S. rivularis, they are, furthermore, widely distributed 

 farther south. Engler,' who has arranged the species in very natural sections, 

 attributed the following geographical distribution to those of the species which 

 occur within our region, i.e., the one explored by the expedition. 



Nephrophyllum: Of the 19 species, representing this section, 10 occur in 

 the mountains of Spain, south of the Pyrenees, and 6 of these are endemic to 

 these mountains; among the others some few are known from the Alps, 

 Caucasus, the Himalayas, eastern Siberia, the Rocky mountains, and Alaska. 



The section Hirculus contains 11 species, 10 of which are endemic to the 

 Himalayas; the eleventh species, S. Hirculus, shows, as may be seen from the 

 table, an extraordinarily wide distribution throughout the northern hemisphere. 



Boraphila with 23 species is mainly Siberian, about 16 species being charac- 

 teristic of the districts between Altai and Kamtchatka, besides western North 

 America; some other species are more widely distributed on this continent, 

 and 9 of these are endemic; several species are also known from the Himalayas, 

 among which 3 endemic. The section is, furthermore, widely distributed in the 

 arctic region. 



While 36 species are attributed to the section Dactyloides, most of these are 

 from Spain, Atlas, and the Canary islands; some few are known from the Car- 

 pathian mountains and the South American Cordilleras; a very few species 

 occur in the Asiatic mountains, but none in the Himalayas. 



With regard to the section Trachyphyllum, most of the species are 

 Himalayan, and only a very few have been reported from Altai, Kamtchatka, 

 western North America, and Central Europe. 



Of the four species representing the section Porphyrion, three are confined 

 to the mountains of Central and South Europe, while the fourth one, S. oppositi- 

 folia, shows an enormous distribution through the northern hemisphere and is, 

 besides, circumpolar. 



The data regarding the distribution of the sections, of which species were 

 collected by the expedition, thus indicate the difficulty in locating the actual 

 centres of their distribution, whether the species originated in the north, notably 

 the arctic region, or in the south. However, with reference to S. radiata Small 

 (S. exilis Steph.), the very limited distribution points towards the centre having 

 been Ic^cated in northeastern Siberia, where it is accompanied by a near ally, 

 S. sibirica. 



S. refiexa Hook., being exclusively arctic and confined to the coast between 

 the Mackenzie and Coppermine rivers, must have originated there. S. aestivalis 

 grows on the north coast of Siberia, but is seemingly rare there; from there it 

 extends to Altai and Baikal, and eastward to Kamtchatka, the coast of Man- 

 churia, and St. Lawrence island. On this continent the species has been reported 

 from Alaska, together with the very local S. Nelsoniana, as well as from the 

 Rocky mountains, as far south as Colorado, and the Cascade mountains. Being 

 apparently very rare in the arctic region as compared with its distribution 

 farther south, and especially in eastern Asia, I presume the centre of both.jS. 

 aestivalis and S. Nelsoniana must have been in northeastern Asia. 



With respect to S. bronchialis, the very wide distribution of this species in 

 the arctic region of Russia and Siberia, and being so very rare on this continent, 

 absent from Greenland and the arctic American archipelago, seems to indicate 

 that its geographical centre may have been located in Siberia, but not necessarily 

 within the arctic region since the species seems to be quite well distributed 



' Monosraphie der Gattung Saxifraga. Breslau, 1872. 



