Clare Island Survey — Marine Algae. 15 105 



70-loU x 7-lU n ; blue-green to olive -green , base nut thickened. Sheaths 

 thin, colourless, or becoming slightly yellow with age ; diffluent above or 

 absent. Trichomes 7-8 /x thick, attenuated, but not ending in a hair (dried 

 specimens only examined) ; cells usually shorter than wide. Heterocysts 1-2, 

 basal or rarely intercalary. 



In Enteromorpha torta Reinke(?). Salt-marsh, Annagh Island, Oct., 1910- 

 This species gives to the Enteromorpha filaments in which it grows a 

 deep, almost black, colour, which caused them to stand out conspicuously 

 against a background of Rhizoclonium. The plant-mass was distinguishable 

 in the field from Oscillaria and Lyngbya, and was collected as a very dark 

 species of Enteromorpha. On examination, however, the tubes were found 

 to contain blue-green filaments, which for the most part were tightly packed 

 along the whole length of the Enteromorpha fronds. A good supply of 

 material was collected, all of which showed the same phenomenon, so that 

 there can be no question of accidental growth. 



Its remarkable habitat renders the plant very distinct ; and except for 

 C. parasitica, no species of similar habit has been described. In the latter, 

 the filaments are embedded in the thallus of Nemalion ; but they occur in 

 fascicles, and project at right angles from the host-plant. The cells of the 

 present species vary considerably in length ; and the lateral walls may be 

 straight or markedly torulose. In October, 1910, the plant was plentiful on 

 the salt-marsh ; but in May, 1911, it was searched for in vain. 



Haplosphaera viridis Schm. 



Mr. G. P. Farran tells me that this species has been noted in the 

 plankton of the Clare Island district during the cooler months of the 

 year. 



The following table, drawn up from Gough's list ('04), is of interest in 

 showing the marked seasonal development of the plant : — 

 Skullmartin (Co. Down), March, April. 



South Arklow (Co. Cork), February- April ; September, October. 

 Coningbeg (Co. Wexford), January- May ; September-December. 

 Fastnet (Co. Kerry). February, March ; (July) September-December. 



Codiolum gregarium Braun. 



Much diversity of opinion exists as to the limits of the species of 

 Codiolum. All the Clare Island forms occurring commonly on the rocks 

 in company with Calotkrix scopulorum, I have referred to C. gregariv.m. 

 The plants vary much in size and length of stalk ; the head in the larger 

 specimens being about 250 fx long by 50-70 p broad, and passing either 



R.I. A. PKOC, VOL. XXXI. O 15 



