RHODOMELACEJE. 101 



below and divided alternately above • lesser branches long, 

 and but little divided; branchlets short, spine-like, awl- 

 shaped, scattered over the whole plant ; tubes in the stem 

 thirteen ; articulations varying, in different specimens and 

 in different parts of the same specimen, from once to thrice 

 as long as broad, visible in all parts of the frond. Spores 

 unknown ; tetraspores in forked branchlets. 



In consequence probably of being a native of deep 

 water this species has been seldom found, and is con- 

 sidered rare. Externally it bears some resembance to 

 Rytiphloea fruticu/osa, but may be easily known by its 

 more slender habit, and the distinct joints of its stem 

 and branchlets. It is annual, and grows during sum- 

 mer, generally on Nullipore banks, in from four to ten 

 fathoms of water. 



Polysiphonia obscura. Hidden Polysiphonia. 



Fronds densely matted together, spreading over rocks or 

 the roots of large sea-weeds, throwing out root-like pro- 

 cesses downwards, and erect undivided branches about half 

 an inch long upwards ; tubes about thirteen ; articulations not 

 quite as long as broad, visible in all parts of the frond. 

 Tetraspores in thickened pod-like branchlets. 



This plant may well be called the hidden Polysiphonia ; 

 for it is so tiny that only a diligent seeker has a chance 

 of finding it. I have no doubt that it grows in many 

 localities where it has been hitherto overlooked. 



Polysiphonia parasitica. Parasitic Polysiphonia. 



Fronds slender, rigid, feathery, alternately branched, from 

 one to three inches long, growing several together from the 

 same base ; branches tripinnate ; branchlets closely set, 



