In this article we will discuss about the external morphology of oedogonium.
1. Plant body consists of green, narrow, unbranched (Fig. 24) and multicellular filaments.
2. Cells are cylindrical and arranged end to end in each filament.
3. All the cells of the filaments are similar in shape except lowermost holdfast and uppermost apical cell.
4. Uppermost apical cell is somewhat broad and rounded at its apex and green in colour.
5. Lowermost basal cell is generally colourless but may contain ill-developed chloroplast and produces certain outgrowths, which help in attachment of the filament to the substratum. It is known as holdfast.
6. Other cells of the filament are similar in structure and green in colour.
7. Some cells of the filaments contain ring-like structures at their upper end. These are known as caps.
8. The number of caps on a cell indicates the number of the times the cell has divided.
9. Each cell (Fig. 25) is surrounded by a wall made up of three layers, the outermost of which consists of chitin, middle of pectose and innermost of cellulose.
10. Cells are uninucleate, and the nucleus is generally present in the middle of the cell but sometimes it is eccentric.
11. A single large reticulate chloroplast is present in each cell. It contains many pyrenoids (Fig. 26).
12. Each cell contains a large central vacuole, which is filled up by cell sap.