Chroococcacece 



347 



is only in one direction, and a number of cells are usually associ- 

 ated to form a small colony. 



Species of this genus occur on wet rocks, among wet mosses, and in bog- 

 pools. Gl, linearis Nag. (length of cells 1O5 18 p; breadth 1'3 2'3/ij 

 fig. 161 A) and Gl. confluens Nag. (length of cells 57 7'5 p. ; breadth 2'6 3 p ; 

 fig. 161 B) are the most frequent British species. 



Rhabdoderma linear e Schmidle 1 seems very closely allied to Glceothece 

 linearis Nag., if not actually identical with it. 



Genus Aphanothece Nag., 1849. This genus only differs 

 from Glceothece in the ag- 

 gregation of large numbers 

 of cells within a common 

 mass of mucus. The cells 

 are cylindrical and longer 

 than their diameter. 



A. microscopica Nag. (length 

 of cells 58 p, breadth 3'5 

 4 p ; fig. 161 C) and A. saxicola 

 Nag. are the most frequent 

 species. They are found in 

 bog-pools, at the margins of 

 lakes, and on wet rocks. 



Genus Synechococcus 



Nag., 1849. The cells, 

 which are cylindrical with 

 hemispherical apices, are 

 larger than in the preced- 

 ing genera, and are desti- 

 tute of the outer mucous 

 coat. They occur free- 

 floating in ponds, ditches, 

 and bog-pools, often in considerable quantity. The cell-contents 

 are usually of a brilliant blue-green, rarely of a rose-purple colour, 

 and contain numerous large granules. 



S. ceruginosus Nag. and S. major Schroeter (length of cells 26 29 p; 

 breadth 15'5 17'5 p ; fig. 161 D and E) are the most abundant British 

 species, the latter often occurring in quantity in bogs. 



Genus Dactylococcopsis Hansg., 1888. The cells are generally 

 associated to form small colonies, rarely solitary, and in many 



1 Schmidle in Berichte Deutsch. Botan. Gesellsch. 1900, xviii, p. 149, t. vi, 

 f. 811. 



Fig. 161. A, Glceothece linearis Nag., from 

 Old Cote Moor, W. Yorks. B, Gl. confluens 

 Nag., from near Settle, W. Yorks. C, Aphano- 

 thece microscopica Nag., from Withiel, Corn- 

 wall. D and E, Synechococcus major Schroet., 

 from Adel Bog, W. Yorks. (All x 450.) 



