••0-. 



\ 





■4%f^' 



Fig. 162 Chroococcus. A, C. turgidus^ plant ( x 600). B, C. turgidusj 

 protoplasmic reticulum with accumulations of metachromatin at 

 nodal points, pg = plasmatic granules, mi = microsomes. C, C. macro- 

 coccus, normal daughter cell formation. D, C. macrococcus, daughter 

 cell formation with retention of the parent envelopes. (A, after 

 Smith; B, after Acton; C, D, after Crow.) 



cytology of this genus has shown that C. turgidus represents the 

 simplest condition with the metachromatin granules only just dif- 

 ferentiated. In C. macrococcus^ a more complex type, there is a 

 central body which is said to contain a fine reticulum with chromatin 

 at the nodal points, but a reinvestigation of this species is desirable 

 and might well lead to a different interpretation (cf Fig. 162). At 

 cell division the reticulum divides by simple constriction, but there 

 is no evidence of a mitosis. The genus is very widespread, the 

 species being either free floating or else forming a component of the 

 soil flora (cf. p. 379). 



Chroococcaceae : Merismopedia (merismOy division; /)^iza, plane). 

 Fig. 163 

 The free floating colonies form regular plates one cell in thick- 

 ness at first, but with increasing age they become irregularly square 

 or rectangular and are often curved or twisted. The cells are 

 spherical or ellipsoidal and their individual sheaths are confluent 



284 



