168 Ulothricaceae 



but containing scattered granules of starch. Cell-wall composed 

 of layers of cellulose which, for the dispersal of zoospores, pull 

 apart in such a way as to leave sections which appear like a letter 

 H in optical section. 



Asexual reproduction by means of 2- or 4-ciliate zoospores, 

 one or two in each cell ; also by means of 2-ciliate microzoo- 

 spores, several formed in a cell (gametes ?) ; germination of both 

 kinds direct. Akinetes and aplanospores are also produced. 



Inhabitants of fresh water. Type M. floccosa (Vauch.) Thuret. 

 [Etym. fAtxp6<z } small, and o-opd, spore.] 



Thuret separated this genus from Conferva on account of the 

 squared appearance of the chromatophore and the method of dis- 

 persal of the zoospores, namely, by the pulling apart of the 

 halves of the cell-wall. 



Both genera were recognized by Rabenhorst ('63, '68) and by 

 Wolle in his earlier study, as is evidenced by his published lists and 

 by labels in his herbarium. Wille ('81), taking no account of 

 chromatophore form, but making an elaborate study of exsiccatae, 

 reunited Microspora with Conferva because he found that in certain 

 species left in Conferva (Tribonemd) the structure of the cell-wall 

 is similar to that described for Microspora. It remained for Lager- 

 heim ('87, '89) to define properly both genera by their chromat- 

 ophore characters and assimilation products. 



A great effort has been made to furnish a contribution to the 

 meager knowledge of the reproductive processes in this genus, 

 but it is a matter of great difficulty to obtain zoospores in any 

 species. We have seen them produced only in two cases, in 

 Microspora floccosa and M. stagnorum. In the case of the former, 

 only a single filament was forming zoospores, and the number ot 

 cilia could not be made out, though the specimen was immediately 

 fixed in osmic vapor. In M. stagnorum the zoospores, which did 

 not seem at all like gametes, had only two cilia, whereas they are 

 usually said to be 4-ciliate. 



Akinetes are frequently seen in most of the species. The 

 filaments become moniliform, the cell-wall thickens and finally the 

 cells fall apart as globose bodies, which, in the mass, resemble 

 resting cells of Chlamydomonas. It is probable that these akinetes 

 usually go through a period of rest before germinating. 



