Clare Island Survey — Phanerogamia. 



10 9 



On Bofin an interesting feature is the scarcity of woodland plants, seven 

 species being absent there which occur on both the other islands, against 

 which no species occurs on Bofin only. The presence of lakelets also makes 

 itself felt by eleven hydrophytes in the "present" list to two in the "absent"' 

 list. Xerophytes are also well represented; sixteen are present; only one 

 absent. In this category it is interesting to note that the influence of 

 calcareous sea-sands makes itself felt in the presence of some distinctly 

 calcicole species, such as AroMs ciliata, Centaurea Scabiosa, Ojphrys apifera, 

 Ceterach officinarum (the last on a dry-built wall). In any case, Bofin 

 enjoys generally a lighter soil, which gives to the flora a more xerophile 

 facies, as is well seen in the great abundance, as compared with the other 

 islands, of Senecio Jacobaea, and the corresponding scarcity of S. aquaticv.s. 



The above analysis of the flora of the three islands may be expressed 

 diagranrrnatically thus : — 



Using the " index of floral diversity " which Colgan has proposed, 1 we 



92 + 26 

 find that this index, as regards Clare and Turk, is — , or - 282 ; as regards 



Clare and Bofin, — , ... , or '300 ; as regards Turk and Bofin, '————, or - 308. 

 4o3 ° '416 



It will be seen that the amount of difference between the floras of the three 



islands is pretty uniform, there being a slightly greater divergence between 



Turk and Bofin than between the two other pairs. This is due to the fact 



that Bofin is best, and Turk is worst, provided with fresh water and with 



sandy beaches. 



It is interesting to see what common Irish plants are absent from this 



group of islands. "We may select for this purpose those species, absent from 



the three islands, which occur throughout Ireland (or the maritime species 



around the whole coast), and are also frequent or common in West Mayo. 



This latter qualification cuts out certain calcicole species, such as Euonymus 



1 Irish Nat., s., p. 236. The index of floral diversity is "the ratio which the total of species not 

 common to both areas bears to the total flora of the two areas combined." 



B.I.A. PROU., VOL. XXXI. B 10 



