38G Mr. Hassall's Notices of British Freshwater Conferva. 



M. Agardh divides the Algae into two classes, of one only 

 of which we have at present to speak, viz. the Zoospores, 

 which are made by Agardh to embrace the following orders : 

 Nostochinee, Oscxllatorice, Conferva, Conjugates, Ectocarpce, 

 Ulvacece, and Siphonacece. It is thus characterized : 



u Materia granulosa interna uniuscuj usque loculi (cellulae 

 articuli vel tubi) frondem constituentis tandem in fructifica- 

 tionem abeunte ; sporidiis maturitate motu praeditis et singulis 

 loculis per porum unicum egredientibus, demum, per exten- 

 sionem evolutis. Viridescentes incolae praecipue aquae dulcis 

 marisque minus salsi, in scrobiculis sinubusque, rarissime in 

 aperto vel profundiori mari." 



From this most extensive class as constituted by Agardh, 

 in which the most diverse productions are evidently embraced, 

 M. J. Decaisne, as already noticed, has removed the Conju- 

 gate of Vaucher, and raised them into a distinct group under 

 the name of Synspores, doubtless on very sufficient grounds ; 

 and I have contented myself with subtracting the true fresh- 

 water Confervae, concerning the reproduction of which such 

 erroneous notions are entertained both by Agardh and M. J. 

 Decaisne ; the opinion of the latter differing only from that of 

 the former in the disbelief of the motion of the zoospores, I 

 feel at the same time assured that it ought to be reduced 

 within still narrower limits. Although I am not disposed to 

 go the length of questioning the existence of the motion of 

 zoospores in all Confervae, I yet feel confidence in doing so in 

 reference to all freshwater Confervae with simple filaments, 

 whether belonging to the group of Synsporece, the Vesicu- 

 laspermcE, or the Sphceroplece, excluding only C. mucosa and 

 C. punctata. 



Many other objections besides those already urged in the 

 course of these remarks might be raised to Agardh^s definition 

 of the zoospores ; but for the present I pass these by, reserving 

 one or two observations, until we come to speak of the zoo- 

 spores as limited by M. Decaisne. 



M. Decaisne thus defines the zoospores, which he makes 

 to embrace only the Nostochince, the true Confervae, and the 

 Ulvacece : " Ont la spore formee aux depens de la matiere verte 

 qui s'organize a l'interieur de chacun des articles ou utricles 

 qui composent toute la plante ; chacun de ces organes peut 

 contenir une seul* ou plusieurs spores." 



And again, M. Decaisne, in another part of his memoir, 

 thus more particularly defines the true Confervae, or Vesicula- 

 spermae : " Les Conferves proprement dites, dont les filaments 

 n'ofirent jamais le curieux phenomene de la conjugation, et 

 chez lesquelles les spores sortent des tubes sous la forme de 



