428 Mr. II, J. Carter on the Development o/" Sorastrum, 



bond of attacliment which extends from centre to centre of the 

 proximate flat triangular sides of the divisions, while two pairs 

 unite to form the zygospore, which is echinated. On the other 

 hand, the individual of Sorastrum is spined only at two ends, 

 the other corner of the cuneate cell being stipitate, while in its 

 normal condition it forms one of a group of eight, sixteen, or 

 thirty-two individuals. The latter, again, do not appear to 

 undergo binary division, but produce one or more baby groups 

 of Sorastrum, and, if we are right in our conjecture, a smooth 

 sporangium, formed probably from the impregnation of a ma- 

 crogonidium by microgonidia. 



Thus the former, by its zygospore, is essentially a Desmid, 

 and the latter, by its mode of generation, essentially allied to 

 Pediastrum (see A. Braun's figures &c. of the development of 

 Pediastrum gramdatum, pi. 3, in ' Rejuvenescence of Nature,' 

 translated in Botanical Reports by Henfrey, Ray Soc. Pub. 

 1853) — a view at which Mr. Archer had also arrived by hav- 

 ing frequently witnessed the evolution of young groups from 

 Coelastrum and Scenedesmus. Hence, in his last letter to me, 

 this able authority states : — " At present, and so far as obser- 

 vation has yet gone, I could assume Sorastrum (as well as 

 Pediastrum, Coelastrum, and Scenedesmus) as not belonging at 

 all to the Desmidicifi." Of course the observations which have 

 led to this conclusion have been made since the last edition of 

 Pritchard was published, in which these genera are all placed 

 by Mr. Archer, as heretofore, among the Desmidiea^. Further, 

 Mr. Archer's present view is also corroborated by Rabenhorst, 

 who [ojy. cit. 1868) has assigned all these genera to his family 

 of Protococcaccee. 



(It is curious, too, as showing the gradual development of 

 our knowledge in these respects among people widely sepa- 

 rated and without intercommunication, although probably of 

 contemporaneous education previously, in the same kind of 

 seminaries, that, in the month of June 1861, I had myself 

 made drawings of Pediastrum, Scenedesmus, &c., to show at 

 some future period that these organisms belonged rather to the 

 Protococcacese than to the Desmidiere.) 



Although, however, Rabenhorst figures and places all these 

 genera under his family Protococcaccaj as "Al</a' unicellulares 

 sensu strictissimo,^^ still a group of eight, sixteen, or thirty- 

 two individuals linked together in the form of Sorastrum can 

 hardly be considered " unicellular," any more than the conca- 

 tenated cells of a filament of Spirogi/ra. But, be this under- 

 stood as it niay, these organisms, tor reasons above stated, un- 

 doubtedly belong nmch more to the Protococcaceie than to the 

 Desmidieas. 



