PLATE V. 



Figures magnified 500 diameters. 



PAGE. 



Figs. 1. 2. PENIUM DJGITUS ; front view and transverse section. (See also 



Plate LXIV,) . . . 34 



Fig. 3. PENIUM CRASSA, four specimens, .... 37 



" 4. PENIUM LAMELLOSUM, . . . . . .34 



" 5. PENIUM MARGARITACEUM ; empty cell, ... 35 



" 6. " zygospore with empty cells attached, 36 



" 7. PENIUM BREBISSONII, zygospore and remains of cells, . . 37 



" 8. " " vegetative cell, ... 37 



Figs. 9, 10. PENIUM TRUNCATUM, and zygospore with husks of cells, . 36 



Fig. 11. PENIUM MARGARITACEUM, vegetative cell, . . 36 



" 12. PENIUM POLYMORPHUM ; group of four, . . .37 



" 13. PENIUM RUPESTRE ; two cell*, .... 38 



" 14. PENIUM INTERRUPTUM, (large form), . . . .36 



" 15. " " (small form), ... 36 



" 16. PENIUM NAVICULA, two sizes of cells, . . . .37 



" 17. PENIUM OBLONGUM, ...... 35 



" 18. PENIUM CLOSTERIOIDES, . ... 36 



Figs. 19, 20. PENIUM MINUTUM, (calocylindrus), ... . . 36 



" 21, 22. PENIUM TRUNCATUM, a variety of Fig. 10, . . .36 



