DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 281 



vegetation witliin the polar circle. I then again went through the catalogue with the 

 herbarium, with every work treating on arctic plants that was accessible to me, and lastly 

 revised it, verifying the habitats, comparing specimens from each province, adding new 

 localities from more recent floras, catalogues, and voyages; tracing the extra-arctic 

 distribution of the species, and noting all points requiring further investigation. 



Tabulated View of Arctic Flowering Flants and Ferns, with their Distribution. 



In tlie appended table of the distribution of arctic plants I have included every species which I know 

 or believe has been found to extend north of 66^° N. lat. Of these, some few may but just cross 

 the polar circle, and hence be scarcely entitled to the term arctic ; but, on the other hand, there are 

 no doubt temperate species which are entitled to be so considered, but which have not yet been recorded 

 from so high a latitude. This remark applies especially to Arctic Siberia, and possibly also in a less 

 degree to Arctic America, where however Richardson's* conscientious researches, conducted with the 

 view of tracing the polar limits of plants, along the valleys of the great rivers Coppermine and Mackenzie, 

 must have left little of importance to be added or corrected. A cross in a column indicates that the 

 species is naturalized. 



The columns showing the distribution of each species are so arranged and filled up as to express in 

 the most simple manner the rather complicated directions of migration of each species or group of species. 

 The leading idea, it will be observed, is to demonstrate the influence exerted by the glacial epoch, and^the 

 columns selected and letters introduced are intended to express the apparent results of this influence on 

 each species, such letters indicating physical obstacles to migrations which the species has or has not 

 overcome. I have hence avoided all further complication than appeared to me necessary to illustrate the 

 conclusions I have an-ived at. It would have been easy to have expressed in greater detail the southern 

 and eastern distribution of the species, subspecies, and varieties in the European column for instance ; 

 but I could not have done so in like manner for the same plants in the Asiatic, nor for any but a few 

 species in the West American columns. 



When the species, subspecies, or varieties grouped under one in these columns shall have been disen- 

 taneled in other countries as they have been in Scandinavia, and when their exact geographical limits also 

 shall be ascertained as accurately in other countries as they have been in Scandinavia, then the time will 

 have arrived for a history of the origin as well as the direction of migration of arctic plants throughout 

 the circle and elsewhere. Meanwhile, as before explained, this essay pretends to no more than laying the 

 foundations of this inquiry on a satisfactory basis. 



The globe is divided into five principal areas; or rather the species are traced in five directions, as fol- 

 lows : — 



I. Arctic Distribution. — 1. Arctic European, from Lapland eastward to the Gulf of Obi. An S. in 

 this column indicates that the plant attains the extreme northern limits of phajnogamic vegetation in this 

 district — viz., Spitzbergen. 2. Arctic Asia, from the Obi to Behring's Straits. 3. Arctic Western Ame- 

 rica, from Behring's Straits eastward to the Mackenzie River. 4. Arctic Eastern America, from the 

 Mackenzie to Baffin's Bay. An M. in this column signifies that the plant extends to the islands north 

 of Lancaster Sound, and to the Parry Islands, including Melville Island, the best explored of them. 

 5. Arctic Greenland. An S. in this column implies that the species has been found south onlj' of the 

 arctic circle in Greenland ; and E. that it is found on the east coast only, the only explored portions of 

 which lie to the north of lat. 70°. 



II. NoKTH AND Central European and North Asiatic Distribution. — From the arctic circle 



* Sir John Richardson has had the kindness to revise the list of arctic plants apjiended to the 2nd vol. of liis ' Boat 

 Voyage through Rupert's Land,' &c. ; and I have his authority for excluding any genera and species whicii ajipcar 

 there, and which are not included in my catalogue. 



