academy ok SciE nc ES .] CENTERS OF DISTRIBUTION. 23 



Lychnis montana Wats. 



This is a member of the section Wahlbergella Fr., of which three species are recorded from 

 the Arctic regions, L. triflora R. Br., L. affinis Vahl, and L. apetala L. L. nesophila Holm is a 

 native of an island north of Hudson Bay, and a variety of L. apetala L., "gracilis Hook," is 

 recorded from the Himalayas at an elevation of 15,000 to 17,000 feet. Wahlbergella is thus an 

 Arctic-Alpine subgenus, and L. apetala L. is circumpolar, but known also from Altai and the 

 Himalayas. Eulychnis Fenzl is represented in North America by only one species, L. Drum- 

 mondii Wats., which is distributed from Canada to Arizona, especially in the mountains, but 

 is not Alpine. Concerning the geographical center of the subgenus Wahlbergella, the cir- 

 cumpolar L. apetala L. undoubtedly originated in the polar mountains; L. affinis Vahl is a very 

 rare plant in Arctic Europe, but not in Greenland, where it extends as far north as 81° 40'; L. 

 triflora R. Br. is known only from Greenland and Grinnell Land, and I presume these two species, 

 L. aflinis Vahl and L. triflora R. Br., were originally developed in Greenland. L. nesophila 

 Holm maj- be looked upon as a descendant of these, and much younger; finally, with regard to 

 our Alpine L. montana. Wats., this may represent a western remnant of the glacial vegetation, 

 and is a close ally of L. triflora R. Br. 



Cerastium arvense L. 



Cerastium arvense L. is very variable in Europe, and according to Koch 20 "variat foliis 

 angustioribus, anguste linearibus, et latioribus, rarius fere ovalibus, erectis, patentibus et 

 reflexis, pilisque pedunculorum glandulosis eglandulosisve, horizontaliter patentibus et reflexis." 

 This author mentions its range as being from the lowlands to the high Alpine regions of the 

 European Alps. Ledebour 21 enumerates several characteristic varieties from Russia and 

 Siberia, and in North America the species appears to be equally common and variable in accord- 

 ance with environment; in recent years a number of these varieties have been raised to specific 

 rank, although the distinction depends mainly upon such variations in structure of leaves and 

 hairs as are already pointed out by Koch (1. c.) , and hardly of sufficient importance to be con- 

 sidered as really specific. The very wide distribution of C. arvense L. naturally points toward 

 the conclusion that certain modifications have taken place, thus the species does not always 

 show the same habit or structure. 



Stellaria umbellata Turcz. 



The mountains of Colorado and Arizona, also the Sierras of California to Oregon, is the geo- 

 graphical range of this species on this continent, but it was in the mountains of Baikal that the plant 

 was discovered and described by Turczaninow. In Colorado the species is one of those that inhabits 

 the highest peaks, the very summits of these, but it descends also to the timbered belts at much 

 lower altitudes; the Rocky Mountains constitute undoubtedly a most important geographical 

 center of this plant, but its occurrence in the Baikal Mountains may indicate that the species 

 developed there, and that it wandered from there to this continent associated with a number of 

 other Siberian types, as, for instance, Smelowskia calycina C. A. Mey. and others. 



Claytonia megarrhiza Parry inhabits the highest peaks, and follows the Rocky Mountains 

 northward to British Columbia. Several other species of the genus occur in these mountains, 

 but at lower altitudes, and it appears as if the Rocky Mountains are an important center of 

 development of the genus. The fact, however, that such Alpine types as O. arctica Adams 

 and O. tuherosa Pall, occur in the mountains of Siberia, Altai, for instance, may indicate another 

 and perhaps much older center of distribution as well as of development; and it deserves atten- 

 tion that the species which illustrate the structure of Arctic-Alpine types are those of which the 

 geographical range is the widest, Altai, Alaska, and Rocky Mountains. 22 



'•" Synopsis Florae Germanieae et Helveticae Leipzig 1857. Vol. 1, p. 107. 

 n Flora Rossica, Vol. 1. Stuttgart, 1841. P. 413. 



k Holm, Theo.: Claytonia Gronov. A morphological and anatomical study. (Nat. Acad, of Sci. Vol. X, Mem. 2. Washington, 1905.) 

 Holm, Theo.: Types of Claytonia. Mindeskrift for Japetus Steeustrup. Kobenhavn, 1913. 



