quirements, while they would fail to do so in any other. These views implied that the sources of our actual vegetation and the explanation of these peculiarities were to be sought in and presupposed an ancestry in Pliocene or still earlier times, occupying the high northern regions. And it was thought that the occurrence of peculiarly North American genera in Europe, in the Tertiary period (such as taxodium, carya, llquidamber, sassafras, negundo, etc.), might best be explained on the assumption of early interchange and diffusion through Northern Asia, rather than by that of the fabled Atlantis. The hypothesis supposed a gradual modification of species in different directions under altering conditions, at least to the extent of producing varieties, sub-species, and representative species, as they may be variously regarded; likewise the single and local origination of each type, which is now almost universally taken for granted.
The remarkable facts in regard to the Northeast American and Northeast Asiatic floras, which these speculations were to explain, have since increased in number, more especially through the admirable collections of Dr. Maximowits in Japan and adjacent countries, and the critical comparisons he has made and is still engaged upon. I am bound to state that in a recent general work by a distinguished botanist, Prof. Guisebach of Göttingen, these facts have been emptied of all special significance, and the relations between the Japanese and the Atlantic United States floras may be said to be more intimate than might be expected from the situation, climate, and present opportunity of interchange. This extraordinary conclusion is reached by regarding as distinct species all the plants common to both countries between which any differences have been discerned, although such differences would probably count for little if the two grew in the same country, thus transferring many of my list of identical to that of representative species, and by simply eliminating from consideration the whole array of representative species—i. e., all cases in which the Japanese and the American plant are not exactly alike. As if, by pronouncing the cabalistic word species the question was settled, or rather the greater part of it remanded out of the domain of science, as if, while complete identity of forms implied community of region, any thing short of it carried no presumption of the kind—so leaving all these singular duplicates to be wondered at, indeed, but wholly beyond the reach of inquiry. Now, the only known cause of such likeness is inheritance, and as all transmission of likeness is with some difference in individuals, and as changed conditions have resulted, as is well known, in very considerable differences, it seems to me that if the high antiquity of our actual vegetation could be rendered probable, not to say certain, and the former habitation of any of our species, or if very near relatives of them in high northern regions could be ascertained, my whole case would be made out.
The needful facts, of which I was ignorant when my essay was
