Range of thallus organisation in Algae

The body structure of algae is a thallus i.e., they doesn’t have well differentiated body structure and exhibit numerous range of thallus organisation, from microscopic to macroscopic structure, unicellular to multicellular, motile to non-motile and many more. This huge range of thallus organisation of algae are discussed below:

1. Unicellular motile:

This is the simplest form of algae. They are unicellular with a rounded, pear-shaped body structure and two flagella at their anterior region. They are motile i.e., they are capable of changing their position. Examples: Chlamydomonas, Euglena, etc.     

2. Unicellular non-motile:

Algae of this type are unicellular, small, more or less spherical, non-flagellate and are non-motile. Examples: Chlorella, Chlorococcum, etc.

3. Multicellular motile:

In this type, a large number of flagellated unicellular algae are embedded together in the gelatinous sheath forming a rounded motile colony. Examples: Volvox, Pandorina, etc.     

4. Multicellular non-motile:

In this type, a large number of non-flagellated unicellular algae are arranged in a single layer along the long axis and thus they are non-motile. Examples: Hydrodictyon, Pediastrum, etc.     

5. Palmelloid:

It is a temporary stage that are formed in some alga where the daughter cells are embedded within a common gelatinous envelope formed by the gelatinisation of the parent cell wall. This daughter cells then divide further forming numerous cells within the matrix which later on become motile by the formation of flagella. Examples: Chlamydomonas and Chromulina.

6. Dendroid:

Dendroid means tree-shaped. In this type, the algal body looks like a microscopic tree. Examples: Prasinocladus, Ecballocystis, etc.     

7. Filamentous:

In this type of thallus organisation, cells are arranged upon one another in a row or in several rows to form a filamentous appearance. This filamentous type may be branched or unbranched. Examples: Ulothrix, Oedogonium, etc.     

8. Siphonaceous:

This type of thallus organisation is made up of long, hollow tube-like structure called coenocyte. Such coenocytic filament have many nuclei and is branched. Examples: Vaucheria, Botrydium, etc.     

9. Heterotrichous:

The term ‘heterotrichous’ is derived from two words ‘hetero’ which means different and ‘trichous’ which means trichome or filament. In this type of thallus organisation the algal body is differentiated into a prostrate branched filaments growing along the substratum and erect branched filaments growing away from the substratum. Examples: Stigeoclonium, Draparnaldia, etc.   

10. Parenchymatous: 

In this type, repeated septation of algal filaments and cell division occurs in two or more planes which results in the formation of parenchymatous thallus like body. Examples: Chara, Fucus, etc.

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