

When placed in water the innumerable thread-like fronds of the 

 Litosiphon stand out from the Chorda, and spread in all direc- 

 tions round it, like the hairs of a bottle-brush. 



This plant was orginally noticed by Capt. Carmichael, who 

 called it Asperococcus pusillus, a name by which it has been 

 generally known to succeeding botanists ; although all have 

 admitted that its claim to be regarded as a species of Asperococ- 

 cus was, to say the least, very doubtful. In the list of species 

 appended to the first volume of this work I called it Chlorosiphon, 

 supposing that it must be the plant called by Kiitzing Chloro- 

 siplion Shuttleworthianus, a name given by that author to an Alga 

 gathered by Mr. Shuttle worth, on the West Coast of Ireland. 

 I made this reference after reading the description in Kiitzing' s 

 work, but a subsequent communication with that author showed 

 me that I had committed an error, for a specimen of Mr. Shut- 

 tleworth's Alga kindly sent to me by Professor Kiitzing, proves 

 to be that young state of Chorda lomentaria, to which Carmichael 

 gave the name Asperococcus castaneus. In these circumstances 

 it becomes necessary to bestow a new name on the present plant, 

 and I have chosen one applicable in a double sense. 



As a genus it seems to come nearest to Dictyosiphon, from 

 which it obviously differs in having an unbranched frond. I am 

 not at all satisfied respecting the nature of the so-called spores, 

 but no other fructification has yet been discovered. 



Fig. 1. Litosiphon pusillus, growing on Chorda filum: — of the natural size. 

 2. Part of a young frond. 3. Part of an older frond, with spores. 

 5. Quarter of a transverse section of the frond: — more or less highly 

 magnified. 



