15 162 Proceedings of the Royal Irish Academy. 



scarcity of records. The fact that the Survey has added about 250 species to 

 Connaught, and over 100 species and varieties to Ireland, shows how little we 

 really know of the distribution of algae. The south-east of Ireland needs 

 special attention ; also south-west Wales, north Cornwall, and the Scilly Isles. 

 Borgesen has pointed out how badly the Shetland algae are in need of 

 re-investigation ('05, p. 787 ; see also '03) ; and the same applies with equal 

 force to north-west Scotland. For Donegal and the coast-line generally 

 between Aehill and Portrush there is hardly a record ; and yet it is along this 

 coast that the southern species disappear and the northern forms, such as 

 Odonthalia dentata, Porphyra miniata, and Monostroma ■f^oscum, begin to show. 

 With regard to France and Spain, although we have good French handbooks, 

 additions to the flora may still be made ; and were it not for Sauvageau's two 

 valuable lists ('97), which are admittedly preliminary, we should have 

 practically no reliable data for the north of Spain. 



For the above reasons I have not attempted to classify the whole flora 

 into definite phytogeographic groups. We may, however, recognize certain 

 well-marked elements, and by means of these attempt to analyse it. 



(a) Southern Element. — Of the species which have a markedly southern 

 distribution, the following are among the most noticeable : — 



Cladophora prolifera. Bostrychia scorpioicles. 



Codium adhaerens. Chondria tenuissima. 



Mesogloia lanosa. Polysiphonia subulifera. 



M. Griffithsiana. P. furcellata. 



Petrospongium Berkeleyi. Dasya corymbosa. 



Cutleria multifida. Spondylothamnion multifidum. 



Bifurcaria tuberculata. Halurus equisetifolius. 



Cystoseira ericoides. Monospora pedicellata. 



C. granulata. Bornetia secundiflora. 



Taonia atomaria. Callithamnion granulatum. 



Dictyopteris membranacea, C. tripinnatum. 



Nemahon elminthoides. Compsothamnion thuyoides. 



Callymenia reniformis. Schizymenia Dubyi. 



Bonnemaisonia hamifera. Corallina squamata. 

 We may mention also eight species which were not found during the 

 Survey, but are known to occur in S.W. Ireland : — 



Asperococcus compressus. Xitophyllum Gmelini. 



Helminthocladia purpurea. Pterosiphonia complanata. 



Gigartina acicularis. Dasya ocellata. 



Xitophyllum Hilliae. Callithamnion tetricum. 



