Plate XXVIII; Figures 181 to 187; Figs. 182, 186 Mag- 

 nified 250 Diameters ; all others 500 Diameters. 



Fig. 181. Spirogyra varians (Hass.) Kiitz. . page 67 

 Fig. 182. 



Conjugating ..... " " 



Figs. 183, 184. Spirogyra Wcberi Kiitz. . " " 



Fig. 185. Spirogyra maxima (Hass.) Witt. 

 Fig. 186. " ' jugalis (Dillw.) Kiitz. . 



Fig. 187. 



Conjugating .... " " 



