338 THE JOURNAL OF BOTANY 



BOTANICAL DIVISIONS OF THE BEITISH ISLANDS. 

 By C. E. Moss, D.Sc. 



In arranging the general plan of the new Cambridge British 

 Flora, one important matter has been to decide whether or not 

 Watson's and Praeger's topographical divisions should be followed. 

 After much consideration it has been decided not to use these 

 divisions entirely, but to have divisions which are understood by 

 the general public and easily ascertainable by foreign botanists. 

 At the same time, it is essential to have the new divisions of 

 such a nature that the mass of accumulated detail regarding the 

 distribution of plants within the limits of the British Isles should 

 be capable of being fully utilized. It is also desirable to arrange 

 the new divisions into larger and, so far as the nature of the case 

 permits, natural phytogeographical groups. 



Accordingly, the divisions adopted follow, in nearly all cases, 

 ordinary British counties. A few of the largest of these are sub- 

 divided into smaller units, and a few of the smallest are merged 

 with neighbouring ones. The counties that are subdivided are 

 Hampshire, Yorkshire, Aberdeenshire, Perthshire, Inverness- 

 shire, Argyllshire, Eoss and Cromarty, and Galway. The counties 

 that are merged with neighbouring ones are Kutland (merged 

 with Leicestershire), Clackmannanshire (merged with Stirling- 

 shire — not with a part of Perthshire as was done by Watson), 

 Kinross-shire (merged with Fifeshire), and Nairnshire (merged 

 with Elginshire — not with a part of Inverness-shire as was done 

 by Watson). The Channel Isles and the Isle of Man are, for the 

 present purpose, treated as if they were British comital divisions, 

 though it is well known that their government is of quite a diffe- 

 rent nature. Many reasons might be advanced for similarly 

 treating the Danish Faroes; but, on the whole, it has been thought 

 best to keep the main unit a political and not a natural one. In 

 doing this one is simply following the plan of practically all floras. 



The botanical and other important characteristics of the various 

 divisions will be elucidated in volume i. of the new Flora ; but, as 

 several other volumes will be issued before this, it has been 

 thought desirable to tabulate the new divisions at once. At 

 present one need only state that the guiding principles in arrang- 

 ing the major divisions (A to T) and the minor divisions (1 to 

 127) have been, first, floristic relationships of -species ; secondly, 

 climate (judged chiefly by the standard isothermal lines) ; thirdly, 

 soil; and, fourthly, topographical position. 



The numbers which appear in brackets after the name of the 

 minor divisions are, in the case of Great Britain, the Watsonian 

 vice-comital numbers, and, in the case of Ireland, the numbers 

 used by Praeger. Of course, one has made the present Irish 

 numbers follow consecutively on the British numbers, and has 

 departed from Praeger's plan of beginning again at number one. 

 It will thus be possible in the future to give a comital number for 

 the whole of the British Isles : in the past, the numbers for Great 



