32 VEGETATION IN COLORADO-HOLM. [MemoieS [vol.xix; 



Polemonium viscosuin Nutt. 



This species is the southern Alpine analogue of the Arctic P. pulchellum Bunge. It is a 

 native of the Rocky Mountains from Montana to Colorado, where several other species of the 

 genus occur, nearly all being endemic. P. pulchellum Bunge is distributed throughout the 

 Arctic regions of both worlds and is almost circumpolar, beside being a native of Altai. 



Eritrichium argenteum White. 



The genus Eritrichium shows several centers with regard to geographical distribution, but 

 the species are relatively local; i. e., confined to certain mountain ranges and regions. E. argen- 

 teum White is a native of the Rocky Mountains, from Wyoming to Colorado, and E. elongatum 

 (Rydb.) White, which is very rare in Colorado, occurs also in Montana and Oregon. E. nanum 

 Schrad. is the only species that is known from the mountains of Austria and Switzerland, and is 

 reported also from the Caucasus. E. aretioides (Cham, et Schlecht.) is a native of northeastern 

 Asia, St. Lawrence Bay, etc., extending from there to Alaska, accompanied by E. Chamissonis 

 A. D. C. E. villosum Bunge is widely distributed through Arctic Russia and Siberia, and has, 

 furthermore, been reported from Baikal. At present E. villosum A. D C. shows the widest 

 geographical range of the species and is a member of the Arctic flora. Similar to Pleuropogon 

 Sabinei R. Br. and a number of other Arctic plants, it has reached the Baikal Mountains, but 

 nevertheless the original center of its distribution and development must have been located 

 in the Arctic mountains. Independently of this E. villosum A. D C, the European E. nanum 

 Schrad., became developed in the Alps of Switzerland, while the other species mentioned above 

 may have developed in West America, probably in the Rocky Mountains. 



THE GENUS MERTENSIA. 



With the exception of Mertensia maritima Don., the other species of the genus are relatively 

 local, and confined to certain mountain ranges. M. maritima Don. is, as we know, widely distrib- 

 uted, in the north especially, from the Atlantic coast, Gulf of St. Lawrence, and Hudson Bay, and 

 westward at various points on the Arctic coast to the Pacific and southward on sea beaches to 

 latitude 49°. Furthermore, the species occurs in Greenland, Spitzbergen, Scandinavia, includ- 

 ing Finmark, Arctic Russia, northeastern Siberia, Kamtschatka, and, finalty, it is not infre- 

 quent in Iceland, Faroe Islands, Great Britain, and Denmark. The Alpine species of Colorado 

 are, on the other hand, confined to these mountains, and several interesting forms have been 

 described in recent years. Mertensia Sibirica Don. occurs at lower elevations in Colorado, 

 and is known also from the higher parts of the Sierra Nevada, California, and far northward, 

 the var. Drummondii Gray having been recorded from the Arctic seashore. Typical M. Sibirica 

 Don. is known also from the mountains of Altai. In the Eastern States M. Virginica D C. is 

 distributed from New York to South Carolina and Tennessee. M. paniculata Don., a very 

 polymorphic species, shows a very wide distribution on this continent: Hudson Bay and Lake 

 Superior, thence to the Rocky Mountains (south to Utah and Nevada) , Alaska, Bering Straits, 

 extending from there to northeastern Asia (fide Gray). No doubt the Rocky Mountains con- 

 stitute an important center in respect to the genus Mertensia, while the Allegheny Mountains 

 are not inhabited by more than one species, M. Virginica D C. According to Ledebour, the 

 Baikal and Altai Mountains are the center of several species of the genus peculiar to Siberia or 



to these mountains alone. 



Chionophila Jamesii Benth. 



The monotypic genus Chionophila is confined to the Alpine regions of the Rocky Mountains 



of Wyoming and Colorado. 



Synthyris alpina Gray. 



This species is a native of the Alpine region of the Rocky Mountains of Wyoming and Colo- 

 rado. Some few other species have been described, and these are mostly from northwest 

 America, one, S. rubra Benth., extending as far north as British Columbia. 



