12 Proceedings of the Roij/d Irish Academy. 



published, and contained a general survey of all Irish species and of their 

 distribution so far as they were known at the time. The section on 

 Algas was written by W. H. Harvey, who afterwards did so much in the 

 investigation of the marine species. In this work, after making certain 

 corrections which a fuller investigation of some species had rendered 

 necessary, 296 species were included. Adopting a modern classification, 

 these were as follows : — 





Freshwater. 



Marine 



Diatomacese, 



. 9 



9 



Cyanophycete, 



. 19 



9 



Conjugata3 







(«) Desmidiaceae, 



. 3 



— 



(&) Other Conjugatte, 



. 7 



— 



Chlorophycete, 



. 35 



28 



Phajophycese, 



. — 



63 



Ehodophycese, 



. 3 



111 



76 220 



Since that date — now over seventy years ago — the present paper is the 

 first attempt to give a general survey of Irish Algfe as a whole, and a 

 census of the species with their distribution. But, as will be seen, several 

 papers were published in the interval giving the distribution of several 

 sub-groups of Algffi in Ireland. 



The most outstanding names in connexion with Irish Algte since 

 Mackay's time are those of Harvey, Archer, and O'Meara. Harvey's work 

 was chiefly among the marine forms, and his " Phycologia Britannica " 

 (1846-51) is still the most authoritative treatise dealing with the species 

 found on the coasts of Britain and Ireland. Archer confined his labours 

 to the study of freshwater forms of life, especially the Desmids; and he 

 read numerous papers on the group before the Dublin Microscopical Club. 

 O'Meara, on the other hand, who also contributed papers to the Dublin 

 Microscopical Club, worked exclusively at Diatoms, freshwater and marine, 

 and it was his intention to publish a complete account of Irish Diatoms. 

 The first part appeared in a paper read before the Eoyal Irish Academy 

 in 1875, and contained 426 species. The final part never appeared, as 

 he seems to have died soon after. 



Important local lists of Alg£e were published in the various Handbooks 

 drawn up in connexion with the British Association's visits to Belfast, 

 Dublin, and Cork. 



Coming down to more recent times, the chief investigators among the 



