caused by the alternately darker or paler gonidia (cellules of the inter- 

 mediate stratum), seen through the superficial layer. The structure is much 

 denser than in Halymenia, more similar to that of Kalymenia. 



Until the fructification of this remarkable plant be discovered, 

 its exact affinities cannot be satisfactorily settled. By Kiitzing 

 it is referred to Halymenia, a genus which at diff'erent times has 

 been made to comprise a number of heterogeneous types. The 

 present species appears to me to be one of such, for judging 

 by the structure of the frond, I should suspect that its position 

 will be nearer to Kallymenia among the genera with compound 

 nuclei {favellidia). Sonder originally described it from very in- 

 complete and discoloured specimens. It is one of the largest 

 and strongest-growing of the Western Australian Bhodosperms, 

 and would require a folio plate to do it adequate justice. Some 

 specimens are very much narrower and more densely branched 

 than the one here figured. 



There is another Western Australian Alga {Nemastoma ? ge- 

 linarioides, Harv.), found at King George's Sound, which bears 

 a striking external resemblance to this plant ; but its structure 

 is difierent and much more dense. Its fruit also is unknown, and 

 the name given to it must therefore be considered provisional. 



Fig. 1. Gelinakia ulvoidea, — the natural size. 3. Section through the frond, 

 — magnified. 3. Minute portion of the cortical stratum : — more highly 

 magnified. 



