238 BRITISH SEA-WEEDS. 



Callithamnion mesocarpum. The middle-fruited 

 C allithamni on . 



Fronds from an eighth to a quarter of an inch high, rising 

 from creeping filaments, erect, simple, or sparingly 

 branched ; branches alternate, naked, or with a few branch- 

 lets ; articulations several times longer than broad, with a 

 transparent margin. Favellae unknown ; tetraspores tri- 

 partite, elliptical, borne on the side branches. 



Captain Carmichael discovered this minute plant at 

 Appin, and described it as " growing on rocks in con- 

 tinuous tufts, forming a broad, shaggy, purple crust." 

 The original specimens are preserved in Sir William 

 J. Hooker's herbarium, and Dr. Harvey has figured them 

 in his ' Phycologia Britannica,' but at the same time he 

 expresses a doubt whether the plant should not be alto- 

 gether erased from the list of species, and referred as a 

 synonym to C. Turneri. Professor Agardh speaks of the 

 species as unknown to him. 



Callithamnion Daviesii. Davies's Callithamnion. 



Fronds about a quarter of an inch high, growing in tiny 

 tufts or continuously, irregularly branched ; branches elon- 

 gate, alternate, spreading ; secondary branches short, alter- 

 nate or secund, one or two only on each primary branch ; 

 branchlets short, secund, springing from the two or three 

 lower joints of the secondary branches, forming what ap- 

 pear to be axillary tufts. Tetraspores tripartite, elliptical, 

 borne on stalks on the axillary branchlets. 



This species is parasitic on Ceramium rubrum and 

 other sea-weeds, and, small as its tufts are, the axillary 

 branchlets are so constantly infested with parasites and 



