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Dublin Microscopical Club. 285 



examples of a protoncmatous growth, otherwise the primordial state 

 of some moss, seemingly, as it were, parasitic on a fern in the College 

 Botanic Garden. These characteristically reddish obliquely jointed 

 filaments seemed in several places as if inserted into and for the 

 time quasi-organically united to the fern, and issuing as hair-like 

 adventitious structures. 



Alliospora sapuectyas, Tim. — Mr. Pirn further showed another 

 state of the fungus brought forward by him at last meeting, with 

 the strings of spores in large tufted heads. 



Cosmarium cymatopleurum, Nordst., and Scottish and Irish Forms. 

 Mr. Archer showed Hcrr Xordstedt's specimen of his Cosmarium 

 cymatopleurnm, var. tyrolicum, also his figure of the 6ame, as well 

 , as that of his original C. cymdopleurum, together with the Scottish 



specimens of Mr. Archer's gathering, in continuation of the exhi- 

 bition at last meeting of Mr. Bissett's form taken from the hills on 

 the Dee-side. The form C. tyrolicum appears, Mr. Archer thought, 

 truly a distinct thing, and it has not occurred in Britain ; so also is 

 probably Mr. Bissett's form distinct from the true C. cymatopleurum. 



Specimens illustrating the Development of Echinus microtuberculatus 



exhibited. — Prof. A. C. Had don exhibited a series of Dr. Dohrn's 



preparations illustrating the development of Echinus microtubercu- 



' lotus, very beautifully showing various stages in development, and 



forming as stained very handsome objects. 



April 20, 1882. 



PWopteris Mertensii. — Dr.E. Perceval Wright, in exhibiting some 

 living specimens of Ptilopteris Mertensii, showed the peculiar manner 

 in which the ramuli bearing the spores (?) broke off, and themselves 

 grew up into perfect plants, which mode of growth had apparently 

 not been previously described. 



Xanthidium concinnum, n. s., Archer, a minute form somewhat of 

 a Cosmarium aspect. — Mr. Archer showed a minute Desmid of rare 

 occurrence, one of those, in their way, interesting forms as to which 

 a decision was difficult as regards their generic position. When met 

 with on the few occasions on which he had detected it, though then 

 in some quantity, he had marked the collecting-bottle " Acute- 

 angled Cosmarium ; " but, as a matter of fact, and taken strictly, 

 the form seemed to fit more properly in the genus Xanthidium. It 

 is very minute (about the size of Cosmarium tinctum), semicells 

 elliptico-hexagonal, the apices bearing at each side and at the upper 

 very obtuse angles a minute but very appreciable muero, each front 

 surface of each semicell showing a distinct median papilla ; end view 

 compressed, showing at the middle on each side the very distinct 

 now prominent papilla. Thus the essentials of the genus Xanthi- 

 dium were fulfilled ; for though the spines were reduced to a mini- 

 mum, they were there, albeit very minute and acute ; and whilst the 



