acadkmv ok sc.ences.] CENTERS OF DISTRIBUTION. 29 



gives the range as follows: "Rocky banks through the subarctic regions and common north- 

 ward, ranging south to the Allegheny Mountains, New Mexico, and the northern borders of 

 California." In Greenland the typical plant is rare, while the var. arctica Lge. is frequent on 

 both coasts. Two other varieties, striata Schum. and uniflora Lge., are also reported from 

 Greenland, but these are quite rare. Typical C. rotundifolia L. is, on the other hand, known 

 from Arctic Europe and Asia, from the European Alps, and Pyrenees, Caucasus, Ural, Baikal, 

 and Altai Mountains. It is evidently a plant of southern origin, but one of those that accom- 

 panied the Arctic vegetation on its return to the north when the ice receded. The very wide 

 geographical distribution through both hemispheres does not exclude the possibility of the 

 species having originated from one single station on this continent or in Europe. Being unques- 

 tionably a lowland plant and as such being much more abundant in Em-ope than in Asia and 

 North America, I presume that middle Europe may have been the original center of develop- 

 ment of the species. Furthermore, in Europe the species is associated with some others of 

 which the general habit is much the same, but of which the capsule is dehiscent near the apex 

 instead of at the base. These species are C. patula L., C. Ranunculus L., and C. persicifolia L. 



Campanula uniflora L. 



This species is almost circumpolar, and it seems natural to suppose that it developed 

 in the Arctic regions. In Siberia it has only been reported from Nova Zembla, Konyam 

 Bay, and Arakamtschetschene Island, but it is absent from Arctic Russia. In North 

 America the species occurs "on the shores and islands of the Arctic Sea from the eastern to 

 the western extremity" (Hooker), and has been recorded from a number of stations in the 

 Alpine regions of the Rocky Mountains south to Colorado. However, the species is one of 

 those of which the geographical range does not include the European Alps or the mountains 

 of Asia, and, as present, it is not known to be abundant anywhere. 



Vaccinium Myrtillus L. and the var. microphyllum Hook. 



These I found growing together with Alpine plants in the deep, cold canyon known as 

 Thompsons Canyon. Typical V. Myrtillus L. is known from Alaska and British Columbia, 

 from there extending as far south as Colorado and Utah. A like distribution within the Rocky 

 Mountains is given of the variety microphyllum Hook. ; of these the former has also been collected 

 in Greenland, but the exact station is not known. In Europe the range of the species extends 

 to the northern borders of Scandinavia, 71° 10' north latitude, and of Russia, but otherwise 

 the plant is much more frequent farther south in the mountains as well as in the lowlands, 

 where I presume it originated. Concerning the variety, this is known only from the Rocky 

 Mountains and Sierra Nevada, California, and mostly occurring at high elevations. 



Arctostaphylos Uva-ursi Spreng. 



This plant reaches the Arctic region in both worlds, and farther south the geographical 

 distribution is the same as that of Vaccinium Myrtillus L. Being more frequent at lower 

 elevations and much more abundant in the cold temperate regions than in the Arctic, it seems 

 safe to conclude that the plant is not of Arctic origin and that the main center of distribution 

 was located in middle Europe. 



Kalmia glauca Ait. var. microphylla Hook. 



This depauperate, Alpine form has been collected at several stations in the Rocky Moun- 

 tains as far south as Colorado and the Sierra Nevada, California, while the typical plant is 

 common in peat bogs from the Atlantic to the Pacific, but scarcely extending north of the 

 Arctic Circle. Neither the species nor the variety have been observed in Greenland, and the 

 genus is altogether confined to this continent and Cuba. 



