238 The Irish Naturalist. December, 



of divisions 1 and 35 is 588 + 184, or 772, and the index of 

 diversity is y?4> or * 2 38, as against an index of "296 already 

 shown for South Kerry as compared with Antrim. 



Taking now the extreme south-east and extreme north-west 

 divisions, Wexford (12) and West Donegal (35), we should 

 expect to find these yielding a higher index than that just 

 shown for the extreme south-west and north-west divisions ; 

 and here again the statistics justify the expectation. The 

 total flora of the two divisions is 818, the total of peculiar 

 species 267, and the index '326, the diversity here being an 

 expression of dissimilarities, both of climate and of physical 

 features. Again, as another instance of diversity between 

 north and south, let us take Wexford (12), in the extreme 

 south-east, and Antrim, in the extreme north-east. The total 

 flora for the two divisions is 860, and the total of peculiar 

 species 254, yielding an index of '295, very slightly lower 

 than that shown for the extreme south-west and north-east. 

 And, finally, before passing from the maritime divisions, a 

 comparison of east and west diversity with north and south 

 diversity may be of interest. Taking Dublin (21) and West 

 Galway (16), both lying in the same latitude, but separated 

 by the whole breadth of the island, we find that the total 

 flora for the two divisions is 845, and the total of peculiar 

 species 275, giving as index "328. This, it will be seen, is a 

 considerably higher diversity than that between South Kerry 

 and Antrim ; a somewhat unexpected result if we take only 

 climatic influences into account. But these influences are 

 strongly reinforced in this case by dissimilarity of physical 

 features and the unequal operation of human agency. 



To touch briefly now on the diversities of some inland 

 divisions, Fermanagh and Roscommon, lying close together, 

 and with floras of almost equal richness, have a diversity 

 index of "25 ; Westmeath and Queen's County, separated only 

 by the breadth of King's County, and having also, like the 

 counties just mentioned, nearly equal floras, yield the higher 

 index of '272 ; while North Tipperary and Kildare, whose 

 surface conditions, relatively the one to the other, are fully as 

 diverse as those of Westmeath and Queen's County, yield the 

 much smaller diversity index of -237, which is yet almost as 

 large as the index for such widely separated divisions as 

 South Kerry and West Donegal. 



