Arctic Plants: Geographical Distribution 107 b 



S. 'reptans where stolons above ground are developed, but otherwise the habit 

 is the same, and the structure of the style, so characteristic of the genus, is 

 identical. 



And, when a small genus like Sieversia has actually been • produced at 

 stations so remote from each other, but in the alpine regions, there seems to be 

 a corresponding probability to suppose that the same species might also be 

 produced independently from more than but a single centre, as long as the 

 conditions are the same, or at least approximately so, in respect to climate and 

 soil and in regard to association with allied types. 



If it were within the scope of this report to include the geographical dis- 

 tribution of alpine species, several instances might be mentioned which would 

 be strongly in favour of Schouw's hypothesis. However, I cannot abstain from 

 recording one, inasmuch as it is a Canadian plant. I think of the discovery of 

 Papaver pyrenaicum L. in the Rocky mountains: South Kootenay pass, Sheep 

 mountain, Waterton lake, besides that I found some specimens in the U. S. 

 Nat. Herb, from Montana: Near Stanton lake, alt. 7,500 feet; these were 

 labelled P. nudicaule. I might state at the same time that Mr. James M. 

 Macoun sent the specimens to the British Museum in order to have my determin- 

 ation verified, and he was informed by the botanists of the said institution that 

 the specimens proved the first record of the species on this continent. 



It would certainly be too strange, I think, to explain the presence of this 

 South European species in the Rocky mountains, as being in any way connected 

 with some centre in the Pyrenees. The stations in both countries are alpine, 

 and the association with allied types is about the same: P alpinum L. and P. 

 nudicaule L. Consequently, it seems probable that P. pyrenaicum originated 

 from two centres: one in the Pyrenees and a second in the Rocky mounta,ins. 



Returning to the arctic species of the Rosaceae, the genus Potentilla is 

 represented by seven species, two of which, P. palustris and P. nivea, are circum- 

 polar; the others, with the exception of P. fruiicosa, are principally arctic types. 

 With respect to P. palustris, this species is nowhere abundant in the arctic region, 

 and it is perhaps one of southern species which accompanied the arctic on their 

 retreat, rather than having actually originated there. P. nivea, on the other 

 hand, is undoubtedly of arctic origin owing to its very wide distribution and 

 frequently abundant occurrence; its occurrence in the Alps, the Pyrenees, Cau- 

 casus, the Altai and Baikal mountains may be explained as it being a remnant of 

 _ a post-glacial vegetation left over on these mountains. But concerning P. 

 pulchella, P. rubricaulis, P- Vahliana, and P. emarginata, these appear to_ be 

 arctic American types, some having extended eastward to Greenland. It is a 

 strange fact that P pulchella occurs in Spitzbergen although it is entirely absent 

 from arctic Europe; perhaps a former more extensive distribution may have 

 been interrupted. 



The circumpolar Rubus Chamaemorus is not uncommon in Central Europe 

 but, nevertheless, it is not represented in the Alps of Switzerland nor in the 

 Pyrenees, and it is also absent from the Rocky mountains; in Greenland it is 

 very rare and has only been found between 61° and 64° N. L. With regard to 

 the occurrence of the species in Canada, John Macoun states that it is especially 

 abundant in the north and that, when found at its southern limit, it always 

 occurs in cold peat bogs; as far south as 53° N. L. it has been found in peat bogs 

 at the base of Porcupine mountain in Manitoba. King William island is the 

 only station known from the American archipelago. It is interesting to notice 

 that in Canada it is often accompanied by Rubus arcticus L., as is the case also 

 with the Scandinavian plant. 



Evidently the habitat "peat bog," where the species thrives at its best, 

 explains its absence from the southern mountains, and the centre of its distribu- 

 tion may be sought in the polar regions, even though it seldom becomes sufficiently 

 advanced to produce mature fruit in these regions. 



