Aquatic - Semi-Equatic - Algae and their 4 Classificaitons

ALGAE 
The Algae are aquatic or semi-aquatic Thallophyta in which all or most of the cells of the thallus normally contain chlorophyll. The simpler types are unicellular, but in the higher forms the thallus may become complicated and of large size, with a considerable amount of cellular differentiation. Except in the Euglenophyceae reproduction is both sexual and asexual. In the simpler members sexual reproduction consists of the fusion in pairs of exactly similar, motile cells, called isogametes, while in the higher types distinct sex organs are developed, which consist of antheridia, the male organs, and oogonia, the female organs. The different gametes produced in these sex organs may be shed and fuse externally (heterogamy), or the emale may be retained within the body of the plant and be fertilized by a motile male gamete (oogamy).
The Algae are classified according to the colour of the pigment present the cells. The following are the more important groups :-

1. Euglenophyceae (Motile organisms, devoid of a cell wall, either colourless or containing chlorophyll, often with various additional pigments. 
2. Chlorophyceae (Green Algae, containing chlorophyll only). 
3. Cyanophyceae (Blue-green Algae, containing phycocyanin in addition to chlorophyll). 
4. Phaeophyceae (Brown Algae, containing fucoxanthin in addition to chlorophyll). 
5. Bacillariophyceae (Diatoms, containing diatomin in addition to chlorophyll). 
6. Rhodophyceae (Red Algae, containing phycoerythrin and phycocyanin in addition to chlorophyll). 

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