With the Cyanophyceae must be included, as their nearest allies, the Bacteriaceae (see Bacteriology).
In the Cyanophyceae the contents of the cell are differentiated into a central colorless region, and a peripheral layer containing the chlorophyll and other coloring matters together with granules of a reserve substance called cyanophycin.
A census of the Cyanophyceae with their two main groups is given below: I.
Glycogen, a substance related to starch and sugar, is found in the Fungi and Cyanophyceae as a food reserve.
The nature of the contents of the cells of Cyanophyceae has given rise to considerable controversy.
Notwithstanding the absence of chlorophyll, and the consequent parasitic or saprophytic habit, Bacteriaceae agree in so many morphological features with Cyanophyceae that the affinity can hardly be doubted.
Bacteria (see BACTERIOLOGY) and Cyanophyceae (see ALGAE), which are often grouped together as Schizophyta, are from points of view of both structure and reproduction extremely simple organisms, and stand apart from the remaining groups, which are presumed to have originated directly or indirectly from the Flagellatae, a group of unicellular aquatic organisms combining animal and plant characteristics which may be regarded as the starting-point of unicellular Thallophytes on the one hand and of the Protozoa on the other.
The existence of ciliated micrococci together with the formation of endospores - structures not known in the Cyanophyceae - reminds us of the flagellate Protozoa, e.g.
The foreign algae are always members of the Cyanophyceae and on the same individual and even in the same cephalodium more than one type of gonidium may be found.
Unknown in Cyanophyceae and Phoeophyceae, known only in Bangiaceae and Nemalion among Rhodophyceae, they are of frequent occurrence among Chlorophyceae, excepting Characeae.