22 VEGETATION IN COLORADO-HOLM. m * mm $2&JS£ 



especially in hilly and mountainous regions," " is hardly correct. Moreover, Thl. cocMeariforme 

 D C. is by no means identical with real Thl. alpestre L. of the European Alps nor with Thl. 

 Suecicum Jord. of Sweden. It is, on the other hand, more safe to consider, at least, the Rocky 

 Mountain species of the genus as distinct from the European. 



None of the perennial species of this genus have been recorded from the Arctic regions, 

 but the annual Thl. arvense L. appears frequently as an introduced weed in Arctic Norway; 

 however, only for a shorter period. The Alps of Switzerland and Germany are the home, and 

 evidently the original, of several species: Thl. perfoliatum h., Thl. alpestre L., Thl. montanumli., 

 Thl. alpinum Jacq., and Thl. rotundifolium Gaud. Of these, the annual Thl. perfoliatum L. has 

 been reported as occurring in Canada (Ontario). A few species are known from the Caucasus: 

 Thl. arvense L., B. baicalense D O, Thl. perfoliatum L., and Thl. umbellatum Gm. jun; from 

 Altai Mountains, Thl. perfoliatum L. and Thl. montanum L. It would thus appear as if the 

 Rocky Mountains and the European Alps are the two principal centers of the genus with regard 

 to development and geographical distribution. 



Smelowskia calycina C. A. Mey. 



This plant inhabits the Alpine summits of the Rocky Mountains from Colorado to Alaska 

 but is known also from Altai, where two other species occur, viz, S. integrifolia C. A. Mey. and 

 S. cinerea C. A. Mey. Of these the latter, together with S. asplenifolia Turcz, are recorded 

 from Baikal by Turczaninow (1. c, p. 285). No doubt the geographical center of these species 

 lies within the mountain ranges of Baikal and Altai, from where S. calycina C. A. Mey. has 

 become distributed across the Bering Strait to Alaska and south to Colorado. 



Cardamine cordifolia Gr. 



It is only seldom that this species occurs above timber line, and, as we know, only a few 

 species, C. bellidifolia L., C. pratensis L., C. digitata Richards, and C. purpurea Cham, et Schl. 

 are recorded from the Arctic regions. Of the species with the leaves undivided some are char- 

 acteristic of the Allegheny Mountains, others of the Rocky Mountains, but 0. cordifolia Gr. 

 does not occur outside the mountains of Wyoming, New Mexico, Colorado, and Arizona. 



Viola bellidifolia Grne. 



Viola bellidifolia Grne is known only from a few stations in Wyoming and Colorado. It is 

 a segregate of V. Muehlenbergii Torr., a native of Labrador and Greenland, reported also from 

 the Allegheny Mountains south to North Carolina, and it is interesting to note that V. canina L., 

 a near ally of these two species, also occurs in the Artie regions of Scandinavia and Russia, as well 

 as in south Greenland. However, in consideration of the prevalence of these caulescent species 

 with their numerous allies farther south, it would be most natural to suppose that the geo- 

 graphical center is located there rather than in the northern regions. V. bellidifolia Grne. has 

 undoubtedly developed in the Rocky Mountains, similar to V. retroscabra Grne., V. Sheltonii 

 Torr., and some of the more or less well-marked varieties of the eastern V. Canadensis L. 



The Caryophyllaceae and especially the Alsineae, exhibit a remarkably wide geographical 

 distribution throughout the northern hemisphere, being able to thrive in the most northerly 

 points and at the highest elevations at which flowering plants are known to exist. Hart 18 

 reports Lychnis apetala from 81° 52', L. affinis from 81° 50', Cerastium alpinum from 82° 50', 

 Stellaria longipes and Alsine verna from 82° 27', and Alsine Groenlandica from 81° 42'. Accord- 

 ing to Hemsley 19 Arenaria Stracheyi grows at an elevation of 19,200 feet in Tibet; Cerastium 

 trigynum, Stellaria subumbellata, and Sagina procumbens are reported from the Himalayas at 

 an elevation of 16,000 to 17,000 feet. 



i' B. L. Robinson in Gray: Synopt. Flora of North America. Vol. 1, pt. 1, New York, 1S95-1S97. P. 123. 



'» Hart, H. C: On the botany of the British Polar Expedition of 1875-1S76 ( Journ. of Bot., 1SS0) . 



» Hemsley, W. B., and Pearson, H. H. W.: On some collections of highland plants from Tibet and the Andes (Journ. of Bot., 1900, p. 238). 



