34 VEGETATION IN COLOKADO-HOLM. [MbmoirS [vo A l TI ^x l 



Polygonum viviparum L., and Oxyria digyna Campd. are circumpolar, and widely distrib- 

 uted throughout the Northern Hemisphere; in Colorado they are quite abundant and typically 

 developed. 



Betula glandulosa Michx. 



This shrub has been found in south Greenland, and the geographical range extends from 

 there to Labrador and Newfoundland westward to the barren grounds of Mackenzie River, 

 through British Columbia to Alaska; it follows the Rocky Mountains as far south as Colorado; 

 in Asia the species is known from eastern Siberia and the Altai Mountains. It does not occur 

 within the Arctic region, and it is very seldom Alpine. Being so widely distributed on this 

 continent, I presume that the boreal regions of Canada are the original home of this species. 



Of the Alpine willows Salix reticulata L. is the only one of interest from a geographical point 

 of view. It is circumpolar, and originated undoubtedly in the polar regions similar to S. polaris 

 Wahlenb. and S. glauca L., which are also circumpolar. 38 



Lloydia serotina Reich, is an Arctic-Alpine type, but it is absent from Greenland, Spitz- 

 bergen, and Scandinavia, and has only been recorded from a few stations in the boreal regions 

 of this continent, viz, northern Arctic coast (Dr. Richardson), St. Lawrence and Ounalashka 

 Islands, Alaska,- 39 thus it is hardly to be defined as a circumpolar species. Lloydia and Allium 

 Sibiricum L. are about the only bulbous plants which so far have been found in the Arctic 

 regions. By considering the geographical distribution, Lloydia has been recorded from several 

 of the higher mountains in Europe and Asia, and its occurrence also in the Rocky Mountains 

 may indicate that it is a mountain type rather than an Arctic. In other words, it is evidently 

 of southern origin, but one of those which accompanied the Arctic plants on their return to the 

 north, when the ice receded. 



JTTNCACEAE. 



Among the Juncaceae, Lusula spicata D C, and Juncus biglumis L. are circumpolar. The 

 latter does not occur in the Alps and Pyrenees, neither in Caucasus, Baikal, and Altai Mountains, 

 nor in the Himalayas. In the Rocky Mountains it was known only from north of Smoking 

 River (fide Macoun, 1. c.) until I found it on Longs Peak, the most southern station, so far, of 

 this species. It is undoubtedly of Arctic origin, and the same is evidently the case of J. castaneus 

 Sm., J. triglumis L., and J. arcticus Willd., although these have been recorded from the higher 

 mountains farther south. Luzula spicata may also be looked upon as representing an Arctic 

 type inasmuch as it is associated in the Arctic regions with several close allies of much the 

 same structure but quite distinct from those which abound in the mountains and lowlands 



farther south. 



With regard to the Cyperaceae, Elyna Bellardii (All.) is an Arctic-Alpine type widely dis- 

 tributed in the Arctic regions cf Europe, less so of Asia and North America; but it is frequent 

 in the Rocky Mountains, also in the European Alps, while in Asia it has been recorded from 

 Caucasus, Alatau, Altai, and Davuria. The genus, as well as Cobresia, has its largest distri- 

 bution in the higher mountains of central or oriental Asia, and especially in the Himalayas, 

 which may be regarded as the center of its development and distribution. 



CAREX. 



In a previously published paper 4 ° I have discussed the geographical distribution of all the 

 species known from Colorado, and with respect to the Alpine types, collected by myself, the 

 following table shows their distribution in general : 



■ Holm, Theo.: Novaia Zemlia's Vegetation. (Dijmphno Togtet's Zoologisk-botaiiiske Udbyttc. Kjobenhavn, 1887. P. 28.) 



» Macoun, John: Catalogue of Canadian plants. Part IV. Montreal, 1S8S. P. 42. 



• Holm, Theo.: The genus Carex in Colorado (Am. Journ. of So., Vol. XVI, July, 1903, p. 17). 



