INTRODUCTION 



As the most westerly portion of the continent of Europe, as it 

 exists at present, Ireland possesses a peculiar interest to the 

 student of botanical geography. This interest is heightened when 

 we find, in the flora of Ireland, living evidence of changes in the 

 distribution of sea and land — changes of great magnitude, involving 

 the whole western edge of the continental plateau, and of consider- 

 able geological antiquity. The range in Ireland of the plants 

 referred to furnishes important testimony regarding the nature 

 and extent of these changes. Furthermore, the distribution not 

 only of these, but of other component groups in the Irish flora, 

 is very suggestive when considered in connexion with the present 

 conditions of situation, soil, and climate, under which they grow. 

 An exact knowledge cff the range of each species in the country is 

 therefore for many reasons desirable ; and the present work is an 

 attempt at a detailed account of Irish plant-distribution, on the lines 

 of Watson's " Topographical Botany," so far as rendered possible 

 by the materials available. 



Let us, first of all, endeavour to obtain a clear general idea 

 of the position and physical characters of the island with which we 

 have to deal. 



I. PHYSICAL DESCRIPTION OF IRELAND. 



Size and Position. — Ireland is roughly elliptical in outline, the 

 longer axis (about NNE. and SSW.) measuring about 300 miles, 

 the shorter (about WNW. and ESE.) about 185 miles; its area is 

 32,524 square miles. The island extends from latitude 51°26'N., 

 to 55° 23' N., and from longitude 5°26'W. to 10°29'W. On the 

 north, west, and south, Ireland is fully exposed to the Atlantic 

 Ocean, and these coasts have suffered much greater marine denu- 

 dation, and are also bolder and more irregular, than the eastern 

 shore-line. A channel, which varies in width from 131 to 150 



