Arctic Plants: Geographical Distribution 121 b 



In other words, some of these arctic representations of Gentiana occur as 

 annuals or biennials, as alpine or lowland plants, and evidently they all have 

 developed in the temperate regions, G. glauca, G. propinqua, and G. arctophila 

 on this contineM, the remaining in Eurasia. However, the occurrence of G. 

 tenella in the Rocky mountains of Colorado is difficult to connect with its wide 

 distribution in Europe unless we presume that the species did originate from two 

 centres, one in the Rocky mountains, and a second in temperate Europe, Scan- 

 dinavia, for instance. And we are confronted with the same difficulty when we 

 attempt to locate the centre for the high-alpine Gentiana frigida Hke. Of this 

 the typical plant is known only from the Carpathian mountains but a variety 

 algida Pall. ((?. Romanzovii Griseb.) occurs in Siberia: Terra Tschuktchorum, 

 Altai and Baikal, besides on this continent in the Rocky mountains of Colorado 

 and Utah; it is recorded also from St. Paul and Shumagin islands, Alaska. I 

 cannot believe that this species developed from -a single centre, in Eurasia or on 

 this continent. The Carpathian mountains as well as Altai and the Rocky 

 mountains constitute centres of the greatest importance to the distribution and 

 development of Gentiana, and the remoteness of these stations in connection 

 with the association of the species with several allied types may, I believe, 

 indicate its origin from these three mountain ranges. ^ 



Pleurogyne carinthiaca Griseb. is a native of the European Alps but it is 

 absent from the Pyrenees; it occurs, however, in Caucasus, Ural, Altai, Baikal, 

 Davuria, Kamtchatka, and the Himalayas (10-13,000 feet); on this continent 

 it has been found in Canada, but only at a very few stations, viz. : Anticosti and 

 RiviSre du Loup, Quebec, besides on the arctic coast explored by the expedition, 

 the only arctic stations thus so far recorded. The wide distribution in the south 

 speaks in f avoiu^ of its actual centre having been located there but it is, of com-se, 

 impossible to decide whether in Europe or in Asia. The occurrence in North 

 America evidently depends on its distribution from Kamtchatka to the islands 

 of Alaska, rather than suggesting an independent development of the species on 

 this continent where it is, as far as we know, so extremely rare and represented 

 only by specimens of diminutive size and very few-flowered. 



The other species, P- rotata Griseb., is in Europe only recorded from arctic 

 Russia while in Asia it is known from Altai, Baikal, and Davuria; it is rare on 

 the west coast of Greenland, between Lat. 60° and 69°, while on the American 

 continent it is distributed from Labrador and Hudson bay to the northwest 

 coast of Alaska; it also occurs in the Rocky mouritains as far south as Colorado 

 where it is'not alpine. It is evidently of southern origin, but of course the actual 

 centre of its distribution cannot be decided. We have thus in the genus Pleuro- 

 gyne two species which are annual and of which the distribution extends across 

 an area of enormous extent throughout the northern hemisphere, but of which 

 p. carinthiaca has reached a wider range in Europe, viz.: to the Alps and 

 Caucasus. It seems strange that the Gentianaceae, though principally high- - 

 alpine, are so scantily represented in the polar regions, and especially by annual 

 or biennial types. 



The almost exclusively American family Polemoniaceae is in the arctic 

 regions but poorly represented. Polemonium boreale is circumpolar, and 

 outside the polar regions it has only been found in the Altai mountains. It is 

 thus absent from the Rocky mountains which otherwise constitute such an 

 important centre of the genus. It would seem very strange if this species were 

 of a more southern origin since, at present, it is almost confined to the arctic 

 region, and especially because, as stated above, it is absent from the Rocky 

 mountains. And with respect to the other species of the genus, the variety 

 villosum is almost circumpolar, while the typical plant is widely distributed in 

 the south, in Europe, Siberia, and on this continent. It actually appears, by 

 considering the geographical distribution of these plants, as if the genuS'has 



