io6 



FRESH-WATER BIOLOGY 



1 8 (17, 19) Colonies at first globular, later irregular in shape, and perforated 

 or netted Clathrocystis Henfrey. 



Cells spherical, united in great numbers to 

 form at first globular, later irregular colonies, 

 which often become clathrate, forming an open 

 meshwork. Common in lakes and ponds; C. 

 aeruginosa Henfr. is often thrown upon rocks 

 along shores to form, mixed with Coelosphacrium 

 kiitzingianum Niig., the so-called "green paint." 



Fig. 38. 



Clathrocystis aeruginosa Henfrey. X 465. 

 (Original.) 



19 (17, 1 8) Colonies irregular in shape, frequently forming films 20 



20 (21, 22) Individual mucous coats clearly evident for each daughter cell of 



the colony Gloeocapsa Ktitzing. 



Cells spherical, with thick, often 

 lamellose, gelatinous membrane; 

 solitary or generally united into 

 microscopic colonies in which the 

 membranes of the daughter cells 

 remain enclosed for a long time 

 within that of the mother-cell. 

 Forming gelatinous substrata on 

 moist walls and wet and dripping 

 rocks. 



Fig. 39. Gloeocapsa polydermatica 

 Kiitzing. X 465. (Original.) 



21 (20, 22) Cells enveloped in a common gelatinous matrix. 



Aphanocapsa Nageli. 



Cells globose, forming irregular colonies enclosed 

 in a thick, homogeneous integument. Differing from 

 Aphanothece only in its globose cells. In stagnant 

 water, on wet rocks, etc. 



Fig. 



Aphanocapsa grevillei Rabenhorst. 

 (After West.) 



X450. 



2 2 (20, 21) Cells globose, reddish purple, arranged in a thin gelatinous stra- 

 tum Porphyridium Nageli. 



Common on damp ground and at the base of damp walls. 



23 (12) Cells solitary or a few adhering together in a group, not forming a 

 definite layer Chroococcus NageH. 



Cells globose or somewhat angular, with firm, often thick, 

 lamellose or homogeneous membrane. Free-floating, or forming 

 a stratum on wet rocks. 



Fig. 41. Chroococcus giganUus West. X 300. (After West.) 



