Genera of Fresh Water Algce. 205 



travel in the same direction, as from Fig. 3 to Fig. 5, and to the 

 left the change will be from Fig. 3 to Fig. 4; this is contrary to 

 what one might at first suppose; a little reflection will show 

 the reason for this. 

 Geneva. N. Y. 



DUBIOUS CHARACTER OF SOME OF THE GENERA 

 OF FRESH WATER ALG^. 



BY REV. FRANCIS WOLLE. 



{^Received February 24th, iSjp.) 



Algologists have made a number of genera of unicellular 

 plants, as Gl(Vocapsa,Aficrocystis,Ghvothece,F>-oiococcus, and the like. 

 My observations of these forms during the past few years in- 

 duce me to question the place given them as plants, and to 

 suggest that they are merely forms of gonidia or spores, or 

 sporangia, various stages of development in the life history of 

 filamentous plants. It has been observed by some authors, that 

 forms of Sirosiphon are developed from cells similar to Ghvocapsa 

 •cells, and that the two kinds of plants live together, also that 

 the articles of the internal cellular structure of Sirosiphon fila- 

 ments are often very similar to the cells of Glxocapsa, but that 

 the one originates the other, and is in turn again reproduced 

 by it, does not appear to have been entertained. This is not 

 surprising, because each form appears to have a life of its own. 

 The filaments develop and multiply, and the spores or gonidia 

 develop and multiply; the latter not unlike some of the lower 

 forms of animal life, as certain Infusoria. In the annexed plate 

 I illustrate three genera of plants, and show how the plants are 

 developed from spores, and how the spores are produced from 

 the plants; and again, how spores reproduce spores often 

 through three or more cycles. These spores represent as many 

 different genera of the so-called unicellular plants. The 

 changes continue through many generations, and sometimes 

 the cells spread over extended surfaces before any of them 

 prove fertile in reproducing the mother plant. 



As an illustration, I represent in Plate XVIII., Fig. i, first a 

 fragment of an old filament {A A) of a common Sirosiphon {al- 

 pini/s). The cells of the plant are usually subspherical and lam- 

 ellate as in the end {B) of the figure. At the other end they 



