Chllorophycae of phylum thallophyta

Phylum Thalophyta - The Algae - Chlorophycae

The Chlorophyceae are Algae in 'which the only pigment is chlorophyll. It is contained in special bodies within the cells, which are termed chloro­plasts. The shape and arrangement of these chloroplasts varies greatly in the different groups, and is frequently used as a means of classification. Among higher plants the chloroplasts are remarkably uniform in shape, but it is evident that the Green Algae are still in an experimental stage of evolution in this respect and that fixity of form has not been attained. 

The lower members are unicellular or colonial. The higher members are mostly filamentous, but a few form flat thalli consisting of cells which divide in two planes. In certain types the body of the organism consists of a ingle giant cell containing many nuclei; such a structure is termed a coenocyte. Occasionally the thallus may be made up of a number of coenocytes embedded in mucilage. 

The Green Algae occur mostly in fresh water, though a few are found in he sea, and some occur on land, but generally in moist situations. In fact quite a large number have been isolated from the soil, though all of very simple types. 

The method of reproduction varies considerably. In some species both 

exual and asexual reproduction occurs, the former either by isogametes or by complex antheridia and oogonia; the latter by small motile bodies termed zoospores. This name recalls the belief of early naturalists that in producing these motile cells the plant was actually turning into an animal. 

The Chlorophyceae are divided into a number of Orders, of which we hall consider types from the following :- 

1. Volvocales (e.g., Chlamydomonas, Haematococcus, Gonium, Pandol'ina, Eudorina, Volvox). 
2. Chaetophorales (e.g., Pleul'ococCUs, Coleochaete). 
3. Ulotrichales (e.g., Ulothrix). 
4. Oedogoniales (e.g., Oedogonium). 
5. Conjugales (e.g., Spirogyra). 
6. Siphonales (e.g., Bl'yopsis, Vaucheria) .
7. Siphonocladiales (e.g., Cladophora). 

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