152 FRESH-WATER BIOLOGY 



127 (no, 128) Colonies somewhat cubical, showing a dark, gelatinous layer 

 between the cells Gloeotaenium Hansgirg. 



Cells globose or flattened, colonies of two, four, or eight cells, with 

 wide lamellate walls. Reproduction by aplanospores. 



FIG. 171. Gloeotaenium loitelsbergerianum Hansgirg. X 220. (After Transeau.) 



128(110,127) Colonies the shape of the individual cells 129 



129 (130) Cells reniform, colony of the same shape or oval. 



N ephrocytium Nageli. 



Cells single or in clusters, as in Sphaerocystis, but reniform in 

 shape. 



: N ephrocytium resembles Oocystis except that the cells are curved. 

 / It is widely distributed but not very abundant. 



FIG. 172. Nephrocytium agardhianum Nageli. X 580. (Original.) 



130 (129) Cells fusiform Elakatothrix Wille. 



Cells elongated, fusiform, gelatinous sub- 

 '- x stance dense, often lamellate. 



FIG. 173. Elakatothrix viridis Wille. X 575- 

 (Original.) 



131 (90, 95, 175) Cells without a thick gelatinous envelop holding them 



together; sometimes adhering to each other after di- 

 vision 132 



132 (137, 155, 174) Reproduction by fission only, or rarely by fission and 



internal division. . . Family PLEUROCOCCACEAE . . 133 



*33 ( J 34> i35> 136) Reproduction by fission in one direction only, forming 

 equal cylindrical cells, the length being one and one-half to 

 three times the breadth Stichococcus Nageli. 



^> <^> 



0g. ^ Chromatophore a parietal plate lying only on one side of the cell, 



v with no pyrenoid. Reproduction by simple fission, the cells sometimes 



<kv ^C=E> & adhering to each other after the division, but not forming perfect 



^ ^ "^ filaments. 



# l\ 



& FIG. 174- Stichococcus bacillaris Nageli. X about 400. (Original.) 



o 



*34 (i33, 135, 136) Reproduction by division in three directions. Cells 

 spherical or, if in small complexes, somewhat angled. 



Pleurococcus Meneghini. 



Cells either single or in small clusters of two, four, or more cells which later 

 fall apart. Chromatophore a thin lining to the membrane with an opening on 

 one side, and with or without a pyrenoid. 



Pleurococcus is the chief constituent of the green coating on the bark of trees, 

 old wood, and stones. 



FIG. 175. Pleurococcus vulgaris Meneghini. X 560. (Original.) 



