328 



NATURE 



{Feb. 6, 1879 



instead of our southern red bay tree. Nor in any of the genera 

 common to the two does the Pacific forest equal the Atlantic in 

 species. It has not half as many maples, nor ashes, nor poplars, 

 nor walnuts, nor birches, and those it has are of smaller size and 

 inferior quality ; it has not half as many oaks, and these and the 

 ashes are of so inferior economical value, that (as we are told) a 

 passable waggon-wheel cannot be made of California wood, nor 

 a really good one in Oregon." 



Prof. Gray then illustrates graphically by diagrams, which we 

 here reproduce, this poverty of the western forest in species in 



1. Atlantic American Forest. 



2. Pacific American Forest. 



3 4 



3. Japan-Manchurian Forest. 



4. European Forest. 



type (of timber-trees) ; it has only 31 genera and 78 species to 

 66 genera and 155 species on the Atlantic side. In the appended 

 diagrams the short side of the rectangle is proportionate to the 

 number of genera and the long side to the number of species. 

 The geographical areas of the two forests are not very different, 

 the length of the Pacific forest making up to some extent for its 

 comparative narro\vness. 



' ' How can so meagre a forest make so imposing a show ? 

 Surely not by the greater number and size of its individuals, so 

 far as deciduous (or more correctly non-coniferous) trees are 

 concerned ; for on the whole they are inferior to their eastern 

 brethren in size if not in number of individuals. The reason is, 

 that a larger proportion of the genera and species are coniferous 

 trees; and these, being evergreen (except the larches), of 

 aspiring port and eminently gregarious habit, usually dominate 

 where they occur. While the east has almost three times as 

 many genera and four times as many species of non-coniferous 

 trees as the west, it has slightly fewer genera and almost one- 

 half fewer species of coniferous trees than the west. That is, 

 the Atlantic coniferous forest is represented by eleven genera 

 and twenty-five species ; the Pacific by twelve genera and forty- 

 four species. This relative preponderance may also be expressed 

 by the diagrams, in which the smaller inclosed rectangles, drawn 

 on the same scale, represent the coniferous portions of these 

 forests. 



"Indeed, the Pacific forest is made up of conifers, with non- 

 coniferous trees as occasional undergrowth or as scattered indi- 

 viduals, and conspicuous only in valleys or in the sparse tree- 

 growth of plains, on which the oaks at most reproduce the 

 features of the 'oak openings' here and there bordering the 

 Mississippi prairie region. Perhaps the most striking contrast 

 between the west and the east, along the latitude usually traversed, 

 is that between the spiry evergreens which the traveller leaves 

 when he quits California, and the familiar woods of various-hued 

 round-headed trees which give him the feeling of home when he 

 reaches the Mississippi. The Atlantic forest is particularly rich 

 in these, and is not meagre in coniferous trees. All the glory of 

 the Pacific forest is in its coniferous trees : its desperate poverty 

 in other trees appears in the annexed diagram. These diagrams 

 are made more instructive, and the relative richness of the forests 

 round the world in our latitude is most simply exhibited, by 



adding two or three similar ones. Two will serve, one for 

 Europe, the other for North-East Asia .... 



"Keeping as nearly as possible to the same scale, we may 

 count the indigenous forest trees of all Europe at 33 genera 

 and 85 species. And those of the Japan-Manchurian region, of 

 very much smaller geographical area, at 66 genera and 168 

 species. I here include in it only Japan, Eastern Manchuria, 

 and the adjacent borders of China, The known species of trees 

 must be rather roughly determined, but the numbers here given 

 are not exaggerated, and are much more likely to be sensibly 

 increased by further knowledge than are those of any of the 

 other regions. Properly to estimate the surpassing richness of 

 this Japan-Manchurian forest, the comparative smallness of 

 geographical area must come in as an important consideration. 



" To complete the view, let it be noted that the division of 

 these forests into coniferous and non-coniferous is, for the 



European non-coniferous, 

 „ coniferous 



Japan-Manchurian non-coniferous 

 „ ,, coniferous 



26 genera, 68 species. 



7 „ 17 M 



33 



85 



47 genera, 123 species. 

 19 ,1 45 .. 



66 



168 



In other words, a narrow region in Eastern Asia contains twice 

 as many genera and about twice as many species of indigenous 

 trees as are possessed by all Europe ; and as to coniferous trees, 

 the former has more genera than the latter has species, and over 

 twice and a half as many species. 



"The only question about the relation of these four forest 

 regions, as to their component species, which we can here pause 

 to answer, is to what extent they contain trees of identical 

 species. If we took the shrubs, there would be a small number, 

 if the herbs a very considerable number, of species common to 

 the two New World and to the two Old World areas respectively, 

 at least to their northern portions, even after excluding arctic- 

 alpine plants. The same may be said, in its degree, of the North 

 European flora compared with the Atlantic North American, of 

 the North-East Asiatic compared with the northern part of the 

 Pacific North American, and also in a peculiar way (which I 

 have formerly pointed out and shall have soon to mention) of the 

 North- Eastern Asiatic flora in its relations to the Atlantic North 

 American. But as to the forest trees there is very little com- 

 munity of species. Yet this is not absolutely wanting. The Red 

 Cedar {Junipcrus Virginiana) among coniferous trees, and 

 Populus treviuloidcs among the deciduous, extend across the 

 American continent specifically unchanged, though hardly deve- 

 loped as forest trees on the Pacific side. There are probably, 

 but not certainly, one or two instances on the northern verge of 

 these two forests. There are as many in which eastern and 

 western species are suggestively similar. The hemlock-spruce of 

 the Northern Atlantic States, and the yew of Florida are ex- 

 tremely like corresponding trees of the Pacific forest ; indeed the 

 yew-trees of all four regions may come to be regarded as forms 

 of one polymorphous species. The white birch of Europe and 

 that of Canada and New England are in similar case ; and so is 

 the common chestnut (in America confined to the Atlantic 

 States), which on the other side of the world is also represented 

 in Japan. A link in the other direction is seen in one spruce 

 tree (called in Oregon Menzies spruce) which inhabits north-east 

 Asia, while a peculiar form of it represents the species in the 

 Rocky Mountains." 



Prof. Gray then asks why the Pacific forest region, which is 

 rich and in some respects unique in coniferous, should be so poor 

 in deciduous trees. And how came California to have the 

 monopoly of the two Big-trees, Sequoias, which have no near 

 relatives anywhere ? " Such relatives," he goes on to say, "as 

 the Sequoias have are also local, peculiar, and chiefly of one 

 species to each genus. Only one of them is American, and that 

 solely eastern, the taxodium of our Atlantic States and the 

 plateau of Mexico. The others are Japanese and Chinese. Why 

 should trees of six related genera, which will all thrive in 

 Europe, be restricted naturally, one to the eastern side of the 

 American continent, one genus to the western side and very 

 locally, the rest to a small portion of the eastern border of Asia ? 

 Why should coniferous trees most affect and preserve the greatest 

 number of types in these parts of the world ? And why should 

 the north-east Asian region have, in a comparatively small area, 



ft i 



