SUB-CLASS V 
CYANOPHYCEA 
THE primitive forms of Algz classified under this 
name possess in all cases a thallus of much sim- 
plicity, being unicellular, or composed of single rows 
of cells, nearly always embedded in definite gelatin- 
ous sheaths or gelatinous masses of indefinite out- 
ward form. The individual plants are in most cases 
associated together in colonies, the tendency to form 
gelatinous envelopes causing them to cohere in this 
fashion. Reproduction is typically a process of 
division of the thallus cells, though the precise 
mode of it, and of the liberation of the propagative 
bodies so formed, varies in the groups into which 
the Cyanophycee are divided. In Chroococcaceee the 
cells are transformed into sporangia. A power of 
movement is exhibited, in the absence of cilia, by 
many members of the group, especially in the pro- 
pagative cells, but this power is sometimes retained 
by the mature thallus, as in the case of Oscillaria. 
The colouring matter of the cells is a bluish-green 
substance, phycocyanine, in addition to chlorophyll. 
