INTRODUCTION. xlix 



moimtain guUies and rock-slielves in many parts of Cork and Kerry. 

 To this south-western sub-group may be added Saxifraga hirsuta, a 

 plant intermediate between S. umhrosa and 8. Geum, but entitled 

 to rank only as a variety. This is of frequent occurrence in the 

 south-west. 



Almost a full degree of latitude separates the northern limit of 

 this di-vision of the Cantabrian group from the southern limit of the 

 second or western division. The latter is made up of the three 

 heaths, Erica mediterranea, Dabeocia poUfoUa, and Urioa MacJcaii, 

 whose area of distributeon in Ireland is confined to the western 

 parts of the counties of Mayo and Galway. The so-called 

 Mediterranean Heath, which, in spite of its name, is nowhere found 

 in the Mediterranean region, occurs abundantly in West Ireland in 

 many stations, from Roundstone in Galway northward to Belmullet 

 in Mayo, over a distance of some 60 miles. Here its early flowering 

 character is well preserved, the plant being usually found m full 

 bloom with us towards the nuddle of March. The more beautiful 

 Dabeocia polifolia, the Connemara or Saint Dabeoc's Heath is 

 quite as widely distributed in the district, for while its northward 

 range from Galway Bay to Curraun AohiH falls considerably short 

 of that of the Mediterranean Heath, its inland extension is much 

 greater. The third member of this sub-group, Mrioa Maohaii, which 

 occurs in the neighbourhood of Eoundstone, is apparently much 

 rarer than either of the others, and its claims to specific rank are 

 perhaps little stronger than those of Saxifraga hirsuta. It can 

 hardly be regarded as more than a sub-species of U. Tetralix. 

 The exclusively western distribution of this Cantabrian group in 

 Ireland is shown graphically on the botanical map issued with this 

 edition. 



Origin of the Cantabrian Group. — Of the many problems in plant 

 distribution, presented by a study of the Irish flora, perhaps none 

 is more perplexing, certainly none has excited more interest or 

 speculation, than the remarkable isolation in Ireland of this 

 Cantabrian group at the extreme northern and western limit of its 

 present European range. It is only in past geological changes that 

 we can hope to find a solution of this problem. The members of 

 the group are undoubtedly iudigenous in Ireland ; and the hypothesis 

 which regards them as relics of a once widespread pre-glacial flora 

 seems to be the one which, however open to objection, presents the 

 least difficulty. Under this view we may assume the group to have 

 ranged in pre-glacial times from the southward into that part of the 



