EXPLANATIONS AND REFERENCES, 

 PLATE CLVI. 



Figures magnified 500 diameters. 



PAGE. 



Fig. 1-3. COELASTRUM MICROSPORUM, . . . . .170 



" 4. Variety speciosum, ...... 170 



" 5. COELASTRUM CAMBRICUM, ..... 170 



" 6-10. SORASTRUM SPINULOSUM, coenobia of various forms, differing 



according to age, . . .171 



Figs. 11, 12. SCENEDESMUS CAUDATUS, typical form. . . .172 



" 13, 14. Smaller forms, . . . . . . .172 



Fig. 15. Var. horridus, . . . . . . .172 



Figs. 10, 17. SCENEDESMUS ANTENNATUS, Var. rectus, . . 172 



Fig. 18-21. SCENEDESMUS DIMORPHUS, different forms, . . 173 



" 22-24. SCENEDESMUS OBTUSUS, various forms, . . . .173 



" 25-26. SCENEDESMUS ACUTUS, two fronds, .... 173 



" 27. SCENEDESMUS ROTUNDATUS, ..... 174 



" 28. DlCTYOSPHAERIUM RENIFORME, . . . . 186 



Figs. 29, 30, DICHTYOSPHAERIUM EHRENBERGIANUM, . . .186 



Fig. 31. A family after Naegeli's figure, . . . .186 



