British North American Plants. 413 



tinctive floras to associated physical and past geological 

 conditions. 



The considerable resemblance between the floras of Japan 

 and the Eiver Amur on the one hand and the Northern 

 United States and Canada on the other, has before now 

 attracted attention. A large number of species are identical, 

 whilst some others in America are represented in Japan 

 and the Amur country by varieties whiGh, no doubt, all 

 have more or less their origin in the changed conditions 

 under which the plants in their new homes exist. The 

 more complete knowledge we now have of the range of 

 these species in Canada, has thrown some new light on the 

 interesting problems which arise in tracing the origin of 

 this identity, and the relations of our flora to that of 

 Europe. Messrs. A. Franchet and Lud. Savatier have in 

 their " Enumeratio Plantarum in Japonia," (Paris, 1879), 

 considerably extended our knowledge of the Japanese flora, 

 and I have taken them as the authority for the occurrence 

 of plants in Japan, whilst Maximowicz is my authority for 

 the plants of the Amur. In a list which I have compiled 

 from Franchet and Savatier's volumes, and which excludes 

 all naturalized plants and garden escapes, there are 221 

 species common to Japan and Canada. The list will be 

 increased, no doubt, as Japan becomes botanically better 

 known. Of this number of identical species, 150 are found 

 in Europe and 85 are also in Alaska. The range of 

 these 221 identical species in Canada, however, suggests 

 some interesting questions. The occurrence of very many 

 European plants in Arctic and temperate America had long- 

 ago attracted attention, and had given rise to various 

 hypotheses, that generally accepted being that in some 

 comparatively recent epoch there had been a connection 

 between America and Europe which had resulted in an in- 

 termingling of the plants of the two continents. In recent 

 years Prof. Asa Gray has suggested the probability of the 

 migration of European plants to America having been 

 across the continent of Asia, and this suggestion he was led 

 to make by finding in Japan many European and American 

 species. After a careful analysis of the range in Canada of 



