Arctic Plants: Geographical Distribution 67 b 



circumpolar nor strictly alpine; it is relatively rare in the polar regions, but it 

 has been recorded from northeastern America, Greenland, Iceland, and Finmark, 

 where it occurs only as what may be termed the "typical" plant. But much 

 farther south and especially in the subalpine zone of the Rocky mountains is a 

 herd of this same species, accompanied by several aberrant forms, besides by 

 species that are apparently distinct, but among its closest allies: C. athrostachya, 

 C. pratensis, C. petasata, etc. Judging from our present knowledge of the distri- 

 bution of C. festiva, its geographical centre seems to have been in the south, in 

 the Rocky mountains, where it is, thus, typically developed, and associated 

 with characteristic varieties, and with allied species. A more complicated case 

 may be illustrated by Carex atrata and C. alpina. The former is only known as 

 arctic in a few stations of Greenland and the European continent, while the 

 latter has been collected in arctic Russia, Finmark, Greenland, and North 

 America, but is more frequent farther south. In the Rocky mountains of Color- 

 ado these species are associated with several allied types, e.g. C. melanocephala, 

 C. bella, and C. chalciolepis ; a close ally of C. atrata, C. ovata, abounds in the 

 northeastern part of this continent, thus illustrating the occurrence of allied 

 types associated with each other. This might indicate the location of the 

 geographical centre as being in the Rocky mountains, so far as concerns the 

 American representatives of C. atrata and C. alpina. In Europe C. atrata is, to 

 some extent, accompanied by two plants, C. nigra and C. aterrima, both of 

 which may be looked upon as immediate allies of this species. And if we extend 

 our comparison of these species with those that occur in the Himalayas, we find 

 there not only C. atrata and C. alpina, but also some deviating forms, and some 

 aUied species, among which C. Lehmannii, C. obscura, C. Duthiei, and C. nivalis. 

 If thus the association with allies in connection with frequent occurrence and 

 tendency to vary may throw some light upon the question as to their centre of 

 distribution, I certainly consider it natural to attribute to these species three 

 distinct centres, one in the Rocky mountains, another in the European Alps, 

 and a third one in the Himalayas. 



Similar results may be obtained by comparing the distribution of other 

 plants, when represented in both "V\^orlds. For instance. Anemone narcissiflora, 

 Lloydia, Elyna, Pyrola, Saxifraga, and several others from the arctic shore are 

 very instructive from this particular point of view. 



24657— .51 



