EXPLANATION OF PLATES. 



PLATE I. 



Fig. 1. A single filament of Oscillaloria cldorina, Kiitzing, magnified 150 diameters. 



Fig. 2. The end of a filament of an Oscillaloria supposed to be identical with 0. Froldichii 

 Kiitzing. 



Fig. 3. 0. nigra, Yaucher. 



Fig. 3 a. Represents a portion of a mat or mass of Oscillaloria nigra, Vauchcr ; there is too 

 much green in the color. 



Fig. 3 b. Represents several filaments separated from the edge of*tJic mass and slightly magni- 

 fied. 



Fig. 3 c. A portion of a filament. 



Fig. 3d. A portion of another filament still more highly magnified. The color in 3 c is more 

 natural than that of 3 d. 



Fig. 4. A portion of a filament of 0. limosa, Agardh, magnified 1250 diameters. Tlje articles in 

 this filament are more distinctly separated than natural. 



Fig. 5. O. neglecta. Wood. 



Fig. 5 a. An outline view of a filament, magnified 450 diameters. 



Fig. 5 6. A full figure of the same, magnified 500 diameters. 



Fig. 6 0. imperalor. Wood. 



Fig. 6 a. Represents the end of a filament, magnified 250 diameters. In the centre of the plate 

 is a fragment (marked simply fig. b.), out of which the endochrome has been partially squeezed to 

 show the markings of the sheath at the joints. 



Fig. T. Ltjngbyabicolor, Wood. Fig. 1 represents a moderately magnified portion of a filament. 

 Fig. a (near to fig. 8) represents a portion of an ordinary filament very slightly magnified. 

 Fig. 1c. A portion of a filament containing a heterocyst, magnified 800 diameters. 

 Fig. Id. A broken end of a filament showing the sheath extending beyond the endochrome, 

 magnified 800 diameters. 



Fig. 8. A variety(?) of Lyngbya bicolor. Wood, from the Schuylkill River, magnified 200 dia- 

 meters. 

 Fig. 9 Cosmarium Qidmbyii, Wood. The bands between tiie cells arc too heavy and prominent. 



PLATE II. 



Figs. 1 b and 1 c. Different stages of germination of the spore of a Cylindrosjiermum of unknown 

 species, magnified respectively 800 and 1200 diameters. 



Fig. 1 a. A chain of spores, believed to belong to the same species; one of these spores has 

 commenced to germinate. 



Fig. 2. A portion of the upper surface of a frond of Nostoc calidarium, Wood. 



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