236 8CYTONEME2E. 



respond with the genus as defined by Mr. Berkeley or 

 myself, neither does his genus Sirosyphon answer to the 

 genus Hassallia, formed by Mr. Berkeley for those species 

 hitherto associated Avith the genus Scytonema, but which the 

 definition of that genus, as it at present stands, does not 

 embrace. 



The following is Kiitzing's definition of Scytonema : 

 " Trichomata vagina duplici, firma crassiuscula colorata 

 arete inclusa ramosa ; rami ex continuatione trichomatis in- 

 terni et prolongatione vaginae oriundi, non basi iis discreta. 

 Spermatia ex articulis intumescentibus progenita." 



In the genus as thus characterised, Kiitzing includes the 

 following British species. Scytonema cerugineo-cinereum 

 ( Ocellatoria rupestris, Grev. Scot. Flor. Turf. 246. ?), S. my- 

 ochrous, S. turfosum, and S. compactum. Now out of these 

 four species there is but one which could be received into 

 the genus Scytonema of Mr. Berkeley, and that one is Scyt. 

 myochrous. It is clear, therefore, that there is no correspond- 

 ence between the genus Scytonema of Berkeley and that of 

 Kiitzing. 



1. SCYTONEMA HIBERNICUM Hass. 

 Plate LXVIII. Fig. 1. 



Char. Filaments of considerable diameter. Cells about as 

 long as broad, issuing in pairs at right angles with the 

 stems. 



Scyt. hibernicum Hassall, MS. 



Hab. On a clayey bank, co. Antrim, Ireland: Mr. 

 Moore. 



Of this beautiful species I have seen but a single specimen. 

 It was sent to me by Mr. Moore, with the name of Scyt. 

 ocellatum upon it, with which plant however it has no affi- 

 nity. The cells are of exactly the same form as in Scy. 

 myochrous, from which it differs principally in being alto- 

 gether larger. 



