256 EXPLANATION OF Til E PLATES. 



Figs. 4 and 4 b. Scytonema cortex, Wood. Portions of filaments, magnified 750 diameters. 



Fig. 5. Piece of a small twig with a well-formed and also a very young frond of Chsetophora 

 elegans, Ag., growing upon it, magnified a few diameters. 



PLATE VII 



Fig. 1. A perfect tricboma of Scytonema cataractum, Wood. 

 Fig. 16. A terminal part of a filament, magnified 250 diameters. 



Fig. 2 a. A portion of a filament of Scytonema immemum, Wood, magnified 750 diameters. 

 Fig. 2 b. Nearly a whole filament or trichoma, amplified 260 diameters. 



Fig. 3. Rhaphidium polymorphum, Wood, different forms, magnified 750 diameters. 



Fig. 4. Protococcus of undetermined species. 



Fig. 4 a. The largest and most mature form, probably the hibernating or Winter cell. 

 Fig. 4 b. The same, commencing its active life. 



Fig. 4 d. Colony cells believed to have been developed out of the cell represented by fig. 4 6, 

 magnified 750 diameters. 



Figs. 4 and 4 c. The motile state of the species. 



PLATE VIII. 



Fig. 1 b. Portion of the frond of Tolypothrix distorta (Miiller), magnified 500 diameters. 

 Frg. 1 a. Heterocysts magnified 800 diameters. 



Fig. 2. Portion of a frond of Sirosiphon pellucidulus, Wood, magnified 260 diameters. 

 Fig. 2 a. End of the branch. 



Fig. 3. Portion of a frond of Sirosiphon compactus (Ag.), magnified 260 diameters. 



Fig. 3 a. End of a filament, magnified 160 diameters. 



Fig. 3 c. Portion of a filament showing the heterocyst magnified 460 diameters. 



Fig. 4. Portion of a frond of Sirosiphon neglectus, Wood. 



Fig. 5. Frond of Sirosiphon guttula, Wood. 



Fig. 5 b. End of a branch, magnified 460 diameters. 



Fig. 6. Portion of a frond of Scytonema Nsegelii, Ktz. 



Fig. 7. Different forms of Qlceocapsa sparsa, Wood, magnified 700 diameters. 



Fig. 8. Merismopedia nova, Wood, magnified 400 diameters. 



PLATE IX. 



Fig. 1. Fragment of a frond of Sirosiphon scylenematoides, Wood. 



Figs. 2 and 2 c. Portions of fronds of Sirosiphon lignicola, Wood, magnified 260 diameters. 

 Fig. 2. The end of a branch of the same, magnified 460 diameters. 



Fig. 3 a Portion of a very old frond of Sirosiphon argillaceus, Wood, magnified 460 diameters. 

 Fig 3 b. A terminal branch of a growing frond of the same. 



Fig. 4 a. A frond of Stigonema RaveneMi, Berkeley, magnified 125 diameters ; also a fragment 

 of the same plant, magnified 450 diameters. 



