in TEMPERATE FLORAS 31 



in about the same average latitude, but with less than one- 

 third the area, has considerably more. The south-eastern 

 States extending to 30 S. lat have about the same number 

 of species as Europe from the Alps and Carpathians south- 

 ward, while the area of the latter is very much smaller and 

 its latitude about eight degrees farther north. 



The whole Mediterranean flora was estimated by 

 Griesbach and Tchikatcheff, in 1875, to comprise 7000 

 species in an area of about 550,000 square miles; so 

 that the best comparisons that we can make between large 

 European and American areas show a decided superiority 

 in the former. This is no doubt partly due to the much 

 severer winter climate in corresponding latitudes of North 

 America ; and perhaps the long persistence of such con- 

 ditions 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 

 northern hemisphere. The great work of Boissier, Flora 

 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 intermingled with luxuriant valleys 

 and plains, and almost tropically warm in its southern portion. 

 So much of it is difficult of access, however, that the collec- 

 tions hitherto made must fall far short of being complete. 

 Its extreme richness in certain groups of plants is shown by 

 the fact that Boissier describes 757 species of Astragalus 

 or Milk-vetch, a genus of dwarf plants spread over the 

 whole 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. Hemsley of the Kew Herbarium) 

 is China and Corea, occupying a little more than i^ million 

 square miles. The enumeration, completed in 1905, shows 

 8200 species of flowering plants actually described. But 

 as large portions of this area have never been visited by 

 botanists, and as new species were still flowing in rapidly at 



