422 Canadian Record of Science. 



Another circumstance would seem to show that the 

 migration may have been across America into Asia. The 

 tendency to variation in plants, will result from or be 

 facilitated by the application of new conditions, and once a 

 variation is permanently established, the plant is unlikely 

 to return to its original form under the influence of a still 

 newer set of conditions. The tendency would rather be to 

 further variation. Now, if a species originating in Europe, 

 migrated to America by way of Asia, and variation should 

 take place in Asia, under the influence of the new set of 

 circumstances which its progress across that continent 

 would present, we would hardly expect to find the plant 

 when it, in the long lapse of time, reached America, return- 

 ing to the original form which it still possesses in Europe. 

 It is much more probable that the American plant, as w'e 

 now find it, must have come direct from Europe, and that 

 the Asiatic variety was the result of the further migration 

 of the American immigrant into Asia under new conditions 

 which assisted variation, or that the European plant 

 migrated both eastward and westward, undergoing change 

 in the one route and preserving its originality in the other. 

 A third hypothesis is that America was the centre of dis- 

 persion. To illustrate these ideas, I give two lists of plants 

 occurring, some on the Amur River, and all in Japan, the 

 one list of species found in both Europe and America, the 

 other of species exclusively American, but each species 

 showing a variation in Japan. My authority for the 

 Japanese varieties are Messrs. Franchet and Savatier. 



American and European. 



Species in America. Represented in Japan by 



Caltha palustris, L C. palustris v. Sibirica, Reg. 



Cerastium vulgatum, L C. vulgatum v. glandulosa, Koch. 



Honckenya peploides, Ehrh H. peploides v. oblongifolia, Gray. 



Vicia cracea, L V. cracca v- canescens, Max., and v. 



Japonica, Mig. 



Linum perenne, L L. perenne v. Sibirica, Mig. 



Humulus Lupulus, L H. Lupulus v. cordifolia, Max. 



Alnus viridis, D.C. A. viridis v. Sibirica, Reg. 



A. incana, Willd A. incana v. glauca, Ait. 



Betula alba, L., in Europe, and v. popu- 



lifoliii, Spach, in Canada B- alba v. vulgaris, Reg. 



