PLATE CXX. 



FIGS. PAGE 



1. Zygospore of Staiirast rum grande. x about 360 

 (after Cushman). Cushman gives the magnifi- 

 cation of this figure as 450 diameters, but this 

 is incorrect according to his own measurements 140 

 2-3. St. grande var. parviim W. & G. S. West. 2, x 



400; 3, x 500 . . . . 141 



4-6. St. Bieneanum Rabenh. 4, x 5UO; 5 and 6, zy go- 

 spores, x 520. The minute punctulations are 

 not indicated 011 the empty semicells of figs. 5 

 and 6 . . . . . 135 



7. St. Bieneanum forma spetsbergensis Nordst. x 



400 (after Nordstedt) . . 137 



8. St. Bieneanum var. ellipticum Wille. x 330 



(after Wille) . . . .137 



9-13. St. aversum Limd. 9, x 400 (after Lundell) ; 

 10, small form, x 500; 11-13, larger forms, 

 x 500 . 144 



