108 HOOKER ON AKCTTC TLANTS. 



been found north of the Arctic Circle in each continent ; then to 

 divide the Polar Zone longitudinally into areas characterised by 

 difFercnces in their vegetation ; then to trace the distribution of 

 the Arctic Plants, and of their varieties and very closely allied 

 forms, into the Temperate and Alpine regions of both hemispheres. 

 Having tabulated these data, I have endeavoured to show how- 

 far their present distribution may be accounted for by slow 

 changes of climate during and since the Glacial Period. 



The Arctic flora forms a circumpolar belt of 10° to 14° latitude 

 north of the Arctic Circle. There is no abrupt break or change 

 in the vegetation anywhere along the belt, except in the meridian 

 of Baffin's Bay, whose opposite shores present a sudden change 

 from an almost purely P^uropean flora on its east coast, to one 

 with a large admixture of American plants on its west. 



The number of flowering plants which have been collected 

 within the Arctic Circle is 762 (Monocot. 214, Dicot. 548). In 

 the present state of cryptogamic botany it is impossible to esti- 

 mate accurately the number of flowerless plants found within the 

 same area, or to define their geographical limits; but the fol- 

 lowing figures give the best approximate idea I have obtained : — 



Filices - - 28 Characese - 2 Fungi - 200? 



Lycopodiacea - 7 Musci - 250 Alga8 - 100 



Equisetacea) - 8 Hepaticaj - 80 Lichenes - 250 



Total Cryptogams - 925 

 ,, Phaenogams - 762 



1,687 



Regarded as a whole, the Arctic flora is decidedly Scandi- 

 navian, for Arctic Scandinavia, or Lapland, though a very small 

 tract of land, contains by far the richest Arctic flora, amounting 

 to three-fourtlis of the whole ; moreover, upwards of three-fifths 

 of the species, and almost all the genera of Arctic Asia and 

 America, arc likewise Lapponian, leaving far too small a per- 

 centage of other forms to admit of the Arctic, Asiatic, and 

 American floras being ranked as anything more than sub- 

 divisions, which I shall here call " Districts," of one general Arctic 

 flora. 



Proceeding eastwards from Baffin's Bay, there is, first, the 

 Greenland District, whose flora is almost exclusively Lapponian, 

 having an extremely slight admixture of American or Asiatic 

 types ; this forms the western boundary of the purely European 

 flora. Secondly, the Arctic-European District, extending cast- 

 ward to the Obi River, beyond the Ural range, including Nova 

 Zenibla and Spitzbergen ; Greenland would also be included in 

 it, were it not for its large area and geographical position. 

 Thirdly, the transition from the comparatively rich European 

 District to the extremely poor Asiatic one is very gradual ; as is 

 that from the Asiatic to the richer fourth or West- American 

 District, which extends from Behring's Straits to the Mackenzie 

 River. Fifthly, the transition from the West to the East- American 



