EXPLANATIONS A^D REFERENCES, 

 PLATE CCVIII. 



Figures magnified 250 diameters. 



PAGE. 



Figs 1, 2. OSCILLARIA IMPERATOR, smaller form, . . 317 



" 3, 4. " typical form, . . .317 



Fig. 5. LEPTOTHRIX HINNULEA, . . 320 



Figs. 6, 7. BEGGIATOA LEPTOMITIFORMIS, two small mats; and single fila- 

 ments, . . . 319 

 Fig. 8-10. BEGGIATOA NIVEUM, two clusters, and single filaments more 



highly magnified, . .318 



Figs. 11, 12. LEPTOTHRIX CAESPITOSA, two caespitose clusters under low 



power, .... 320 



Fig. 13. LEPTOTHRIX HERBACEA, . . 320 



" 14. LEPTOTHRIX OCHRACEA, 

 " 15. LEPTOTHRIX RIGIDULA, ...... 321 



" 16. LEPTOTHRIX TINCTORIA, . . 321 



Figs. 17, 18. LEPTOTHRIX LAMINOSA, ... 321 



Fig. 19. LEPTOTHRIX BULLOSA, . . . 321 



" 20. " single filaments under higher power, . 321 



" 21. LEPTOTHRIX CALCICOLA, (muralis), . . . 319 



