294 PROCEEDINGS OF SOCIETIES. 



and watched it in all stages, and felt quite satisfied that the mature 

 zygospore was now exhibited. 



Several other forms rarely found conjugated were also shown, 

 such as ^antliidiumfasciculatiim, Staurastrum cuspidatum, Arthro- 

 desmus convergens (always with a zygospore without spines), A. 

 incus, Euastruon ohlongum, E. didelta, JE. elegans, Docidium 

 Ehrenhergii, and others. 



Further, amongst the zygospores shown were those of Micras- 

 terias rotata and M. denticulata. This latter had not before been 

 met with in Ireland in the conjugated condition. It was pretty 

 abundantly taken on the late Club excursion to Tinnehely. Some 

 of the present examples were, however, from near Carrig Moun- 

 tain, where Mr. Archer had taken it, associated with M. rotata, 

 also conjugated ; and ^ now exhibited examples of both on the 

 ' same slide. The zygospore of M. rotata had not been recorded 

 till he met with it last year sparingly in Wales, and a few weeks 

 subsequently in Co. Wicklow, and here it turned up again along 

 with that queen of zygospores, so far as elegance and size are 

 concerned, that of M. denticulata. These are quite unlike, in 

 fact more so than are the forms themselves, abundantly distinct 

 as these are. M. rotata has a larger zygospore than M. denticu- 

 lata, and is beset by elongate, simple, subulate, acute spines ; 

 whereas, as is well depicted in Rails', that of Jil. denticulata is 

 smaller, and beset with shorter, much-branched spines, the 

 branches finally curved downwards. These are, however, scarcely 

 strictly spines, but rather hollow, branched processes, the granu- 

 lar contents from the central general cavity of the spore reaching 

 often a good way up the tube ; they are at first fringe-like cylindri- 

 cal projections, ultimately acquiring thicker walls, and becoming 

 branched. Mr. Archer could not help regarding the very decided 

 difierences in the zygospores of these two common species as a 

 conclusive argument for their specific distinctness, for which he 

 had, indeed, on other grounds, long contended. 



Mr. Crowe likewise showed examples of the zygosjDore of 

 Micrasterias denticulata taken at Tinnehely. 



Dr. John Barker showed examples of the conjugated state of 

 Closterium lunula, for the first time seen in Ireland. These 

 were quite in accord with , the figures given by De Bary, and de- 

 scribed in his work ' Untersuchungen iiber die Familie der Con- 

 jugaten,' p. 48. It would seem not to be quite certain that the 

 figures given by Mori'en, and called G. lunula, do not, some of 

 them at least, apply to G. Ehrenhergii, a species quite distinct 

 from the former. 



Mr. Archer showed, new to Ireland, Didymolielix ferruginea 

 (Griflith, in ' Micrographic Dictionary') = GaUionella ferruginea, 

 (Kiitz.). This elegant, excessively minute,doubly spiral filament 

 is an excellent test for the higher powers to resolve into its two 

 component helically coiled fibres, though they often occur not 

 intertwined. This plant seems to bear a relationship to Lepto- 

 thrix comparable to that of Oscillatoria to Spirulina. 



