The articulations are pellucid in all parts of the frond, and composed of four 

 tubes surrounding a minute cavity ; the lower ones are several times as long 

 as broad, the upper gradually shorter, and the ultimate ones scarcely exceed 

 their breadth. No fruit has yet been observed. The colour is a beautifully 

 brilliant rosy-red, well preserved in drying, in which state the plant adheres 

 firmly to paper. The substance is soft and very flaccid, but not gelatinous, 

 and the frond does not rapidly decompose in fresh-water. 



This delicate little species of Polysiphonia, which is not done 

 justice to in our figure, being represented somewhat coarser 

 than nature, was dredged in considerable plenty by Mr. Clifton 

 and myself in June, 1854, in the anchorage off the mouth of 

 the Swan River. I have not detected it elsewhere, nor received 

 it from correspondents, and am unacquainted with its fruit. 

 It appears to be most related to the European P. formosa, or 

 to the Antarctic P. abscissa (recently found in Tasmania), but 

 differs from both sufficiently in ramification, etc. The specific 

 name is bestowed in honour of J. S. Roe, Esq., R.N., Surveyor- 

 General of Western Australia, in which capacity he has explored 

 many distant portions of the Colony ; and, though not a bota- 

 nist, never neglects an opportunity of promoting botanical re- 

 searches. I was much indebted to his kindness during my visit 

 to Western Australia. 



Fig. 1. Polysiphonia Roeana, — the natural size. 2. Part of a small branch, 

 with ramuli. 3. Two of the lower joints. 4. Upper joints. 5. End of a 

 ramulus. 6. Cross section of the frond : — the latter figures more or less 

 magnified. 



