220 DARWINIANA. 



geographical distribution. The point to be remarked 

 is, that many, or even most, of the genera and species 

 which are peculiar to North America as compared with 

 Europe, and largely peculiar to Atlantic North Amer- 

 ica as compared with the Calif ornian region, are also 

 represented in Japan and Mantchooria, either by iden- 

 tical or by closely-similar forms ! The same rule holds 

 on a more northward line, although not so strikingly. 

 If we compare the plants, say of New England and 

 Pennsylvania (latitude 45°-47°), with those of Oregon, 

 and then with those of Northeastern Asia, we shall find 

 many of our own curiously repeated in the latter, 

 while only a small number of them can be traced along 

 the route even so far as the western slope of the Rocky 

 Mountains. And these repetitions of East American 

 types in Japan and neighboring districts are in all de- 

 grees of likeness. Sometimes the one is undistinguish- 

 able from the other ; sometimes there is a difference of 

 aspect, but hardly of tangible character; sometimes 

 the two would be termed marked varieties if they grew 

 naturally in the same forest or in the same region ; 

 sometimes they are what the botanist calls representa- 

 tive species, the one answering closely to the other, 

 but with some differences regarded as specific ; some- 

 times the two are merely of the same genus, or not 

 quite that, but of a single or very few species in each 

 country ; in which case the point which interests us 

 is, that this peculiar limited type should occur in two 

 antipodal places, and nowhere else. 



It would be tedious, and, except to botanists, ab- 

 struse, to enumerate instances ; yet the whole strength 

 of the case depends upon the number of such in- 



