The Vegetation of Japan. 
45 
exclusion of other species, in Central Japan grow singly or in small 
groves on the lower border of Tsuga forests or mingled with broad¬ 
leaved trees. In northern Japan and on the high mountains of 
Honto, birches are more abundant than they are in the northern 
forests of America, and the river banks in the north, like those of 
N. Europe and Siberia, are lined with arborescent willows and 
alders, which are rare in eastern America, where these genera are 
usually represented by shrubs. This difference is due to the other 
dominant plants peculiar to each flora. The nnmber given in 
Gray’s estimation should also be reduced slightly, since he included 
as natives some Chinese and Corean plants cultivated in Japan. 
Besides these and some endemic species, we have, as I have 
already remarked, a great many plants of the boreal region of the 
old world. For instance, Asperula odorata which occurs in Europe 
but not in America, grows abundantly in North Japan. In South 
Japan many tropical and sub-tropical elements may be seen. 
Certain plants growing in the central and southern parts of the 
country have also a close affinity to those of S. China as well as to 
those of the Himalayas. 
IV.— Regions of Vegetation. 
As has already been said, owing to the considerable length of 
the Empire, we cannot deal with the vegetation collectively, but 
are bound to divide it into certain regions. It may conveniently be 
arranged in three divisions mainly based on the climatic conditions:— 
(1) Northern, (2) Middle, and (3) Southern Regions. The Northern 
Region extends from the 38th degree of latitude northwards to 
the Kuriles and Saghalien. We may also include in it the northern 
part of Corea. The Middle Region is formed of the greater part of 
Honto and Shikoku, a small part in the north of Kyushu, and 
South Corea. The Southern Region includes the southern parts 
of the province of Kii and Shikoku, the greater part of Kyushu, 
the Bonin Islands, the Loochoos, Formosa, and the Pescadores. 
We must note here that within each of these regions there 
exists a certain degree of difference in the vegetation, according as 
we consider the northern or the southern portion. The northern 
part of the Northern Region is represented by the arctic, and the 
southern part by the sub-arctic, with a few elements of the cold 
temperate flora. In the northern part of the Middle Region the 
plants of the cold temperate flora are to be found, and in its 
southern part those of the warm temperate. The Southern Region 
