DIVISION CYANOPHYTA 



In this division the cells are without chromoplastids, the pigments 

 being diffused generally throughout the peripheral portion of the 

 protoplast. In some forms the pigments occur as granules crowded 

 and somewhat localized just within the cell membrane. Besides the 

 usual complement of pigments found in the green algae (although 

 chlorophyll-b is lacking in the Cyanophyta), phycocyanin (water- 

 soluble ) and myxophycean phycoerythrin may be present. Different 

 concentration and combinations of these pigments are responsible 

 for the multitudinous colors exhibited by the blue-green algae. 



Photosynthetic products are glycogen and glycoproteins rather 

 than starch. Frequently proteinaceous granules ( cyanophycin ) are 

 present. There is no definite nucleus, although the presence of 

 chromatin bodies has been proved in the central region of the cell. 



Usually the cells or colonies of individuals are invested by muci- 

 laginous substances, which may be either soft and watery or firm 

 enough to form a definite sheath. The cell membrane is thin and is 

 composed of two layers, the outer one gelatinous and contributing 

 to the investing mucilage. Many forms contain pseudo vacuoles 

 which are dark and refractive and sometimes cause the cells to 

 appear black, reddish, or purple. According to some investigators, 

 these are gas vacuoles; others identify them as pockets of mucilage. 



Reproduction occurs principally by fission and by fragmentation, 

 but in some of the filamentous members, akinetes, sometimes referred 

 to as gonidia, function as reproductive cells. Sexual reproduction is 

 unknown in the Cyanophyta. In a few forms, endospores may be 

 employed. These are especially characteristic of the Chamaesipho- 

 nales where gonidia-like bodies are formed from the protoplast by 

 either simultaneous or successive constrictions or divisions. 



Colonial organization is very simple, and the range of architecture 

 is limited, the branched trichome being the climax of structural 

 complexity. 



As interpreted here, the Cyanophyta include 2 classes, the blue- 

 green algae or Myxophyceae, and the Chlorobacteriaceae, a group 

 of pigmented, bacteria-like organisms. 



CLASS MYXOPHYCEAE 



The Chamaesiphonales and Chroococcales constitute the tribe 

 Coccogoneae, and the Hormogonales the tribe Hormogoneae of 

 some authors. 



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