156 HEREDITY AND EVOLUTION IN PLANTS 



these two regions. The skunk-cabbage (Symplocarpits 

 Jcetidiis, Fig. 72), species of Magnolia, Hydrangea, 

 Hamamelis (witch-hazel), Liquidambar (sweet-gum), Ara- 

 lia (ginseng), Eupatorium, Onoclea (sensitive fern), Ly co- 

 podium (L. lucidulum), and scores if not hundreds of other 

 species, have a similar type of distribution. 



Similarity of Floras of Eastern Asia and Eastern 

 North America. The similarity in the floras of eastern 

 North America and eastern Asia and Japan was first 

 pointed out by Asa Gray, 1 in 1859, on the basis of his 

 study of the plants collected in Japan in 1855, by Charles 

 Wright, botanist of the U.S. North Pacific exploring ex- 

 pedition. Of 580 Japanese plants of this collection 

 Gray found only 0.37 per cent, having representatives in 

 western North America, while 0.6 1 per cent, has repre- 

 sentatives in eastern North America; for identical species 

 the corresponding percentages were 0.27 per cent, and 0.23 

 per cent. Of 56 Japanese species not known in Europe, 

 22 were known from eastern but not from western North 

 America. Exploration subsequent to the date of Gray's 

 paper has altered our knowledge of the distribution of 

 many species in the region referred to, but the broad 

 fact pointed out by Gray has only been confirmed by more 

 careful investigation. 



Several writers 2 have called attention to the fact that 

 various species of plants and of invertebrate animals are 

 confined to the west of Ireland and North America. 



1 Gray, Asa. On the botany of Japan, and its relations to that of North 

 America, etc. Botanical Memoirs, extracted from Vol. VI (New Series) of 

 the Mem. Amcr. Acad. Arts and Sciences. Boston and Cambridge, 25th 

 April, 1859. 



2 E.g., Colgan, N., and R. W. Scully. Cybcle Hibcrmca. 2d Ed. p. 

 71. Scharff, R. F. Proc. Royal Irish Acad. 28: 13. Nov., 1909. 



