84 THE WORLD OE LIFE 



sistence of siicli conditions before the glacial period may be 

 the main cause of the whole phenomenon. 



It is, however, in temperate Asia that we find what seem 

 to be the richest extra-tropical floras, at least in the north- 

 ern hemisphere. The great work of Boissier, Elora Orientalis 

 (1880), describes 11,876 species in the region of East Europe 

 and South- West Asia, from Greece to Afghanistan inclusive, 

 the area of which may be roughly estimated at 2,000,000 

 square miles. It is a region of mountains and deserts inter- 

 mingled wdth luxuriant valleys and plains, and almost trop- 

 ically warm in its southern portion. So much of it is diffi- 

 cult of access, however, that the collections hitherto made 

 must fall far short of being complete. Its extreme richness 

 in certain groups of plants is showm by the fact that Boissier 

 describes 757 species of Astragalus or Milk-vetch, a genus of 

 dwarf plants spread over the w^hole northern hemisphere, but 

 nowhere so abundant as in this region. Europe has 120 

 species. • 



The only other extensive area in temperate Asia the plants 

 of which have been largely collected and recently catalogued 

 (by Mr. W. B. Ilemsley of the Kew Herbarium) is China 

 and Corea, occupying a little more than 1% million square 

 miles. The enumeration, completed in 1905, shows 8200 

 species of flow^ering plants actually described. But as large 

 portions of this area have never been visited by botanists, 

 and as new species w^re still flowing in rapidly at the close 

 of the enumeration, there can be little doubt that the total 

 will reach, before many years have elapsed, 10,000 or per- 

 haps 12,000 species. It is, moreover, an area that is es- 

 pecially rich in trees and shrubs, and as these are less col- 

 lected by the travelling botanist than the herbaceous plants, 

 it becomes still less easy to speculate on the actual number 

 of species this country really contains. Japan, which is prob- 

 ably better known, has about 4000 species in less than one- 

 tenth the area, and is thus a little richer than Erance. It 



