PLATE XLVI. 



Figures magnified 500 diameters ; the Micrasterias 375 diameters. 



PAGE. 



Fig. 1. MICRASTERIAS ALATA, . . . . . .125 



" 2. MICRASTERIAS MAMILLATA, . . . . 126 



" 3. MICRASTERIAS DKNTICULATA, zygospore, . . .120 



" 4. STAURASTRUM ARCTISOON, Var., . 163 



" 5. COSMARIUM CONSPERSUM, Var. retusum, front view, . . 82 



" 6. COSMARIUM BIRETUM, Var. Floridense, front view, . 93 



Figs. 7, 8. STAURASTRUM COHMARIOIDES, front and vertical views, . 139 



" 9, 10. STAURASTRUM BREVISPINA, Var. inerme, . . . 134 



" 11, 12. STAURASTRUM CORNUTUM, front and vertical views, . . 158 



