brownish in drying. Substance very rigid, horny when dry, in which state 

 tlie plant does not adhere to paper. 



My first acquaintance with this plant was from a specimen 

 given me in 1838 by Mr. James Backhouse, and I then placed 

 it, unhesitatingly, in the genus Mhodomela ; but did not publish 

 it with a name. Afterwards, in 1845, Sonder described it, from 

 Preiss's specimens, under the name Trigenea australis, which 

 name I adopted in the 'Nereis.' Lastly, in 1854, having col- 

 lected personally, and received from Mr. Clifton, Dr. Curdie, 

 and Dr. Mueller, more perfect specimens, I return to my earlier 

 opinion, and replace it among the Rhodomela, retaining Sonder's 

 name " Trigenea " for the species. So far as the fructification 

 is known, it agrees with Rhodomela, and there is nothing in 

 structure or habit which compels us to put it in a different 

 genus. The multiplication of generic groups which have no 

 strongly marked limits, is one of the banes of modern botany. 



Eig 1. Ehodomela Trigenea, — the natural size. 3. A ramulus, with cerami- 

 dium. 3. Cross section of the ramulus : — the latter figures variously mag- 

 nified. 



