PLATE CXXIL 



FIGS. PAUE 



1-5. Staurastrum tumidum Breb. All x 400. 1-3, 

 triangular forms ; 4, vertical view of quadran- 

 gular form ; 5, zygospore (after Lundell) . 142 

 6. St. Clepsydra Nordst. x 400 (after Nordstedt) 152 

 7-10. St. Clepsydra var. sibericum (Borge) W. & Gr. S. 

 West. 7, x about 330 (after Borge) ; 8-10, x 

 T)20. 7 and 8, forma ovalis; 9 and 10, forma 

 trigona . . . .152 



