446 Proceedings of the Royal Irish Academy. 



Stictyosiphon (Kiitz.), Rke. 



In ttis genus plurilocular sporangia only are known ; the 

 tips of the branches are jointed and end in three hairs. 

 S. tortilis, Eke. (includes S. sul-articulatus, Hauck, of Holmes and 

 Batters' Revised List). 12 IST. 



Striaria, Grev. 



The tips of the filaments are tapering, the unilocular zoo- 

 sporangia are arranged in superficial dot-like zones. 



S. attemmta, Grev. 



11 Mc. 12D.M. 12 T. 12 H. 14 K 



Desmotriclium, Kiitz. 



B. undulatum, Rke. ION. 



The hairs are solitary ; the unilocular and the plurilocular 

 zoosporangia project from the thallus surface. 



Pxtnctaria, Grev. 



The dots on the thallus are in some cases due to the sori of 

 sporangia, in other cases to the tufts of hairs. The two are 

 distinct. Both unilocular and plurilocular sporangia are known 

 in all the British species. 

 P. plantaginea, Grev, 



On all the coasts. 



P. latifolia, Grev. 



Probably not less common than P. ijlantaginea. 



P. tenuissima, Grev. 



On all the coasts, probably. One of us formed the opinion 

 some time ago that P. tenuissima, though found fertile, is 

 simply the young spring state of P. plcmtagijiea and P. latifolia, 

 which are not so specifically distinct as is often described. 

 Dr. Moore has one specimen labelled "seemingly intermediate." 



Order IV. — Aspeeococcace^. 

 Myriotricliia, Harv. 



M. clavceformis^ Harv. 10-14. 

 M. filiformis, Harv. 10-14. 



Asperococcus, Lamx. 



The hairs and sori of sporangia occur mixed together ; in 

 this respect Asperococcus differs from Punctaria. The pluri- 

 locular zoosporangia were discovered by Buffham. 



