336 Mr. HassalPs Notices of British Freshwater Conferva. 



XLIL— Observations on a new Group, Genus and Subgenus, of 

 Freshwater Conferva, vnth descriptions of Species mostly 

 new. By Arthur Hill Hassall, Esq., M.R.C.S.L., 

 Corresponding Member of the Dublin Natural History 

 Society. 



[Continued from p. 47.] 



Vesiculasperm^e. 



Char. Filaments simple, slightly tapering, usually attached, 

 not conjugating, in their young condition cylindrical, articu- 

 lated ; extremities lanceolate ; spores usually either oval or 

 spherical, each contained in a separate enlarged cell not un- 

 frequently of the same form as the spore. 

 My first impression with respect to the species contained 

 in this group was, that it would be sufficient to regard them 

 as constituting a new genus ; subsequent reflection and ex- 

 amination have however convinced me that they should hold 

 a higher than a generic station, and that it would be more in 

 accordance with strict propriety to consider them as forming 

 a separate group. 



In addition to the distinctive characters indicated in the 

 definition given above, viz. the tapering of the filaments, and 

 the production of spores without union of the filaments, which 

 spores are usually contained in inflated cells, the Vesiculaspermce 

 are distinguished by other, though somewhat less obvious not 

 less important characteristics. The filaments are of a firmer 

 texture than other freshwater Confervae, they possess compara- 

 tively but little flexibility, are not mucous, and consequently do 

 not exhibit that glossy appearance presented by so many Con- 

 fervae when removed from the water, and which they retain 

 when dried upon paper, in all which particulars they stand in 

 marked opposition to that numerous and important division of 

 the freshwater Confervae, the Conjugates of Vaucher, which 

 have been recently denominated by M. Decaisne, Synspore'es ; 

 in all the species of which division the filaments are flexuous, 

 mucous and shining in the highest degree ; in these too the 

 filaments never taper, but are always exactly and equally cy- 

 lindrical, and the spores, with the four exceptions alluded to 

 in the observations already published on the genera Zygnema 

 and Mougeotia, are invariably formed by the admixture and 

 union of the contents of two cells of different filaments. More- 

 over the joints differ in the two groups : in the Vesiculaspermce 

 they are strongly marked, and when dried become con- 

 tracted and dark-coloured ; while in the Synspores they are 

 faintly indicated, and in dried specimens are often with diffi- 

 culty discoverable. 



