KXPLANATION OP THE PLATES. 255 



Fig. 7 b. The first broaking-up of the contents of the large cell into a brood of cells. 

 Figs. 7 d ami 7 c. Different stages in the life of the latter brood-cells and their progeny. 



PLATE IV. 



Fig. 1. Mastiyonema fertile, Wood, a single plant (not magnified 750 diameters, as marked on 

 tbi- plutc). 



Fig. 1 b. A hcterocyst magnified 750 diameters, also a spore cell and spore similarly amplified. 



Fig. 3 o. A portion of the frond of Mastigonema scjunctum, Wood, amplified 250 diameters. 

 Fig. 2 b. A single filament magnified 800 diameters. 



Fig. 3. A single filament of Zonotrichia mollis, Wood, enlarged 260 diameters. 



Fig. 4. A section of the frond of Zonolrichia parcezonala, Wood, magnified a few diameters. 



Fig. 5. The base of a filament of Dasyactis mollis, Wood. 



Fig. 5 a. Section of the frond, magnified 450 diameters. 



Figs. 5 b and 5 c. Young filaments; each magnified 450 diameters. 



Fig. 0. Fronds of Caelosphaerium dubiitm, Wood. 



PLATE V. 



Fig. In. A portion of the frond of Masligonema elongatum, Wood, slightly magnified to show 

 tin' filaments radiating from the fragment of matter to which they are attached. 

 Fig. 16. A single filament magnified 4GO diameters. 



Fig. 2 c. A cluster of youngish filaments of Mastigonema halos, Wood. 



Fig. 26. A portion of an older filament to show the spore-like divisions of the cndochrome, miig- 

 nified 400 diameters. 



Fig. 3. A pair of young connate filaments of Masligoihrix fibrosa, Wood, magnified 450 

 diameters. 



Fig. So. An old filament magnified 800 diameters. 



Fig. 36. A young filament with heterocyst, enlarged 450 diameters. 



Fig. 3d A filament with two basal cells magnified 450 diameters. 



Fig. 4 o. A portion of filament of Scytonema Ravenellii, Wood, magnified 160 diameters. 

 Fig. 4 6, The end of a branch magnified 450 diameters. 



Figs. 5 o, 6, c, &c. Different forms of Chroococcus refraclus, Wood. Fig. 5 A is not a good 

 one. I was not able to express well the peculiar translucent shining tint, and the artist who copied 

 my drawing failed even more decidedly in simulating it ; the pink shade is altogether wrong, I 

 never saw any such color in the plant. 



Fig. 6. Different forms of Chroococcus multicolor at us, Wood. 



Fig. 6 c. Represents what was thought to be possibly a hybernating form of the species. 



PLATE VI. 



Fig. la. A portion of a frond of Scytonema thermale, Ktr., magnified 260 diameters. 

 Fig. I 6. Outline sketch, showing the form of the heterocyst, magnified 750 diameters. 



Fig. 2. Trichoma or frond of Scytonema callitrichoides, Ktz., amplified 250 diameters. 



Fig. 3 a. Outline sketch showing the cells or chambers of Scytonema dubium, Wood, magnified 

 750 diameters. 



Figs. 3 6 and 3 c. Portions of the filaments or tricboma, magnified 460 diameters. 



