10 NATURAL HISTORY SOCIETY OF DUBLIN. 



markable combinations of conditions, not only in their vegetative parts, 

 bnt also in their reproductive organization, which render them exceed- 

 ingly interesting, and in many points of view highly instructive. That 

 they should reproduce themselves by zoospores — thisphenonemon having 

 been now so long known and observed in so many Algae — may not be 

 surprising ; but they are also amongst those of the humbler Algae, in 

 which, thanks mainly to Professor Pringsheim's masterly researches, 

 a true reproductive process by the mutual co-operation of distinct 

 sperm-cells and germ-cells — a true fertilized spore — was first known to 

 be formed.* 



With the exception of the species of (Edogonium and Bulbochsete 

 described by Pringsheim and de Bary, I am not acquainted with those 

 of any other author which I can regard as of any value. Indeed, I 

 think it would be vastly better had these never before been described at 

 all, and the more advisable course seems to be to ignore them. Possibly, 

 indeed, the plant I now bring forward may have been met with and de- 

 scribed before ; but, inasmuch as the distinctions hitherto put forward in 

 OEdogonieoe are founded, not on the characters presented by the fructi- 

 fication, but simply on comparative dimensions of the vegetative parts, 

 it would be impossible to be certain. Therefore, in the present instance, 

 the only course seems to be to follow Pringsheim, and name the present 

 plant on the characters offered by the reproductive organization. The 

 fact is, that it is quite possible that the true species in the (Edo- 

 goniese are by no means so numerous as are the pseudo-species re- 

 corded in books, on what seem to be, at least comparatively, unessen- 

 tial characters. 



In the Family of the (Edogonieas, besides the long-known asexual 

 mode of propagation by means of zoospores, which here are produced, in 

 the ordinary cells destined thereto, by the formation of the whole of the 

 contents into a single zoospore with an anterior wreath of cilia, there 

 also occur three types of sexual fructification — namely, a monoecious 

 and a dioecious type, as well as a third kind, partaking somewhat of 

 the nature of each, denominated by Pringsheim, " gynandrosporous." 



In the monoecious and dioecious groups the antheridia are formed 

 from one or several very short adjacent cells of the same or different fila- 

 ments from those bearing the oogonia (as the case may be) ; the contents 

 of each of these cells, with a single exception, do not at once give rise 

 to antherozoids (spermatozoids), but the cell becomes divided by a very 

 delicate transverse, or, in one instance, r vertical, septum, into two 

 daughter-cells, each of which latter becomes the special-mother- cell of 

 a single antherozoid, in form like a minute zoospore. This escapes 

 generally by the circumscissile dehiscence of the antheridial cell, 

 though Yaupell describes a species (CEdog. setigerum), in which it 

 escapes by a lateral aperture. f 



* " Jahrbiicher fur wissenschaftliche Botanik," Bd. I., p. 1, " Morphologie der OEdo- 

 gonien." 



f " Jagttagelser over Befrugtningen hos en art af Slsegten (Edogonium." 



