15 H4 Proceedings of the Royal Irish Arwhmji. 



tetrasporic fruit.- were collected in Februai v. The flabellate 

 arrangement of the cells on the under-surfaoe of the thallus(a feature which 

 Schmiti makes characteristic of the genus) distinguishes it at "nee, in our 

 area, from allied plants. 



Harvey records C. Dvbyi (sub 1' dia Dvbyi)a& occurring in great 



profusion in Birturbuy Bay, Roundstone (" Phyc. Brit") : but, as pointed out 

 below, this was an error, since the specimens preserved are thos 

 Peyssonnelia. It is remarkable that in Clew Bay Cruoriella should be 

 dominant, and at Roundstone Peyssonnelia. 



Peyssonnelia up. 



The Bpecies of Peyssonnelia occurring in west Ireland must for the 



present remain undetermined. It was recorded by Harvey as P. Dvbyi (new 

 Cruoriella Dubt/i): and he states that it is abundant in Birturbuy Bay. 

 Batters ('96, p. 11) showed that Harvey *s material consisted of a genuine 

 Feyssonnelia (the T.C.D., Kew, and Linn. Soc. material was examined , and 

 he referred the plant to P. rubra Grev.,a species originally described from the 

 Ionian islands, and, as generally understood, common in the Mediterranean. 

 Though the genus is correct, the specific identity appeared questionable. 

 From Greville's description, his species is a plant with free-growing Lobes, 

 i.e. with the habit of P. aguamaria ; whereas the Clew Bay plant has an 

 attached encrusting thallus, such as is found in P. Harvevana. In order to 

 settle the point it was necessary to examine the type in Greville's herbarium 

 at Edinburgh ; and through the kindness of Professor Bayley Balfour, it was 

 sent to Kew on loan. The specimens fully confirmed Greville's description and 

 figure, and there is no doubt that the Irish species must be kept distinct. 

 Madame "Weber van Bosse, who is engaged in unravelling the tropical species 

 of the genus, informs me that the form of the rhizoids, to which much value 

 has been attached, is an unreliable character. The species of this, and allied 

 genera, have in the past been so poorly described, that it is impossible to be 

 certain if any of them are identical with the present plant. On this account 

 it appears advisable to wait till a monographic work is available. The 

 alga is rare in Clew Bay, and fruits in winter. 



Porphyrodiscus simulans Batters. 

 On account of its characteristic nemathecia, the genus Porphyrodiscus was 

 founded by Batters for the reception of this plant (Journ. Bot., 1897, p- 4D9>. 

 He detected it at Berwick in 18S9. and apparently it has not been found 

 elsewhere. The Clew Bay specimens were obtained at Annagh Island, on 

 stones in muddy ground near low-water mark. 



