591 



made by Prof. Asa Gray.* I quote the abstract of his views given in his 

 "Address". 



The singular relations between the Japanese flora and that of North- 

 eastern America gave rise to the speculations which were published 

 "before Heer had developed the rich fossil botany of the arctic zone; before 

 the immense antiquity of existing species of plants was recognized ; and 

 before the publication of Darwin's now famous volume on the 'Origin of 

 Species' had introduced and familiarized the scientific world with those now 

 current ideas respecting th.e history and vicissitudes of species with which I 

 attempted to deal in a moderate and feeble way. 



"My speculation was based upon the former glaciation of the northern 

 temperate zone, and the inference of a warmer period preceding and perhaps 

 following. I considered that our own present vegetation, or its proximate 

 ancestry, must have occupied the arctic and subarctic regions in Pliocene 

 times, and that it had been gradually pushed southward as the temperature 

 lowered and the glaciation advanced, even beyond its present habitation ; that 

 plants of the same stock and kindred, probably ranging round the arctic zone 

 as the present arctic species do, made their forced migration southward upon 

 widely different longitudes, and receded more or less as the climate grew 

 warmer; that the general difference of climate which marks the eastern and 

 the western sides of the continents — the one extreme, the other mean— was 

 doubtless even then established, so that the same species and the same sort 

 of species would be likely to secure and retain foothold in the similar climates 

 of Japan and the Atlantic United States, but not in intermediate regions of 

 different distribution of heat and moisture ; so that different species of the 

 same genus, as in Torreya, or different genera of the same group, as Redwood, 

 Taxodium, and Glyptostrobus, or different associations of forest-trees, might 

 establish themselves each in the region best suited to the particular require- 

 ments, 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 higher northern regions. And it was thought that the 

 occurrence of peculiarly North American genera in Europe in the Tertiary 

 period (such as Taxodium, Carya, Liquidambar, Sassafras, Negundo, &c.) 

 might be best explained on the assumption of early interchange and diffusion 

 through North Asia rather than by that of the fabled Atlantis.' 7 



•Memoirs of the American Academy of Arts and Sciences, vi, pp. 3/7-458, 1859. See also his 

 address at the Dubuquo meeting of the American Association for the Advancement of Science, held 

 August, 1872. See also American Naturalist, vi, 577. 1872. 



