Gray • The Similarity Between the Flora of ]apan ' 47 



ably ranging round the arctic zone as eastern American and Asiatic floras 

 the present arctic species do, made which these speculations were to ex- 

 their forced migration southward upon plain have since increased in number, 

 widely different longitudes, and re- especially through the admirable col- 

 ceded more or less as the climate grew lections of Dr. Maximowicz in Japan 

 warmer; that the general difference of and adjacent countries, and the critical 

 climate which marks the eastern and comparisons he has made and is still 

 the western sides of the continents — engaged upon. 



the one extreme, the other mean— was I must refrain from all enumeration 

 doubtless even then established, so of the angiospermous or ordinary de- 

 that the same species and the same ciduous trees and shrubs, which are 

 sorts of species would be likely to se- now known, by their fossil remains, to 

 cure and retain foothold in the similar have flourished throughout the polar 

 climates of Japan and the atlantic regions when Greenland better de- 

 United States, but not in intermediate ser\'ed its name and enjoyed the pres- 

 regions of different distribution of heat ent climate of New England and New 

 and moisture; so that different species Jersey. Then Greenland and the rest 

 of the same genus, as in Torreya, or of the north abounded with oaks, 

 different genera of the same group, as representing the several groups of 

 redwood, Taxodium, and Glyptostro- species which now inhabit both our 

 bus, or different associations of forest eastern and western forest districts; 

 trees, might establish themselves each several poplars, one very like our bal- 

 in the region best suited to the par- sam poplar or balm-of-Gilead tree; 

 ticular requirements, while they would more beeches than there are now, a 

 fail to do so in any other. These views hornbeam, and a hop-hornbeam, 

 implied that the sources of our actual some birches, a persimmon, and a 

 vegetation and the explanation of these plane tree, near representatives of 

 peculiarities were to be sought in, and those of the Old World, at least of 

 presupposed, an ancestn,' in Pliocene Asia, as well as of atlantic North Amer- 

 or earlier times, occupying the higher ica, but all wanting in California; one 

 northern regions, And it was thought Juglans like the walnut of the Old 

 that the occurrence of peculiar North World, and another like our black wal- 

 American genera in Europe in the nut; two or three grapevines, one near 

 Tertiary period (such as Taxodium, our southern fox grape or muscadine, 

 Car}'a, Liquidambar, Sassafras, Ne- another near our northern frostgrape; 

 gundo, etc.) might be best explained a Tilia, vev)' like our basswood of the 

 on the assumption of earlv interchange Atlantic States only; a Liquidambar; 

 and diffusion through North Asia, a magnolia, which recalls our M. gran- 

 rather than by that of the fabled At- diflora; a Liriodendron, sole representa- 

 lantis. five of our tulip-tree; and a sassafras. 



The hypothesis supposed a gradual very like the living tree, 



modification of species in different di- Most of these, it will be noticed, 



rections under altering conditions, at have their nearest or their only living 



least to the extent of producing va- representatives in the Atlantic States, 



rieties, sub-species, and representative and when elsewhere, mainly in eastern 



species, as they may be variouslv re- Asia. Several of them, or of species like 



garded; likewise the single and local them have been detected in our Tertiary 



origination of each type, which is now deposits, west of the Mississippi, by 



almost universallv taken for granted. Newberry and Lcsqucreux. Herbaceous 



The remarkable facts in regard to the plants, as it happens, are rarely pre- 



