T. H. BUFFHAM ON ANTHERIDIA. 301 



Spermothamnion hermaphroditum Nag. has already been 

 mentioned. 



Antithamnion plumula Thur. (CalUthamnion plumulaJjyTigb.^ 

 — Long, thin, flexuous trichogjne. 



Halarachnion ligulatum Kiitz. (Halymenia ligulata Ag.) 



Polyides rotundus Grev. With fecundating tubes. 



CoralUna o'fficinaUs L, 



C. rubens Ellis et Sol. (Jania rubens Lamour.) 



I have said supra that the external portions of the parasitic 

 alga Choreocolax Folysiphonice are devoted to the production of 

 the reproductive organs. Cystocarps may be distinguished 

 from the others by the surface showing large brown cells 

 through a brown epiderm. Usually an ovoid, lobed form of 

 '5- "7 mm. in length comprises several cystocarps, and each has 

 a conspicuous ostiole about 30 /x in diam. Sections show a 

 remarkable structure differing considerably from that of any 

 other British alga. Mr. Richards {loc. cit.) has very fully 

 described and figured American specimens. The carpospores 

 line the whole of a deep ovoid cavity. I do not, however, see 

 them quite as he draws them. Instead of the spores being of 

 a nearly uniform size and regularly placed, while each is 

 accompanied by a slender paraphysis of the same height, my 

 sections show, at regular intervals, groups of spores in different 

 stages of maturity, with very few slender bodies that may be 

 barren threads. The tetrasporic specimens — of a similar size, 

 but globose — exhibit a surface in which the apices of the cells 

 are loosely set in gelatine with the tetraspores interspersed. 

 They resemble tetrasporic specimens of Harveyella mirahilis 

 (Fig. 41). In a section the tetraspores of Ch. Polysiphonice are 

 found to be elongated, and cruciately divided. (Folkestone, 

 June 1892, collected by Mr. Neeve). 



The female specimens of H. mirahilis usually consist of 

 groups of globose or ellipsoidal cystocarps, each about 1 mm. 

 in diam., which may be distinguished with a low power as the 

 greater part of a cystocarp is dark within. This is surrounded 

 by a concentric light zone, and this again by another less light 

 just within the surface (Fig. 40). In a vertical section we 

 observe another instance of structure differing from that of all 



