Oedogonium sp. Hirn, 1900
This is a fliamentous alga. The unbranched filament is made up of cylindrical cells with certain cells having transversely striated walls at the distal end. The basal cell is modified into a holdfast and the apical cell is usually broadly rounded or acuminate. All cells except the basal have the capacity to divide. The cells have a single nucleus each and a single reticulate chloroplast that completely encircles the protoplast.
Oedogonium is epiphytic on other aquatic algae or water plants. it may also be attached to stones or free floating objects. It is usually found in small permanent bodies of water like pools and ponds. The filaments may also occur as free floating masses.
Vegetative propagation is by fragmentation of the filaments. Asexual reproduction is through zoospores, formed singly within a cell. The zoospores are ovoid to pyriform, each with a ring of flagella at the anterior end. On germination, the zoospore gives rise to a 1-celled structure that anchors itself to the substratum and begins to divide and subdivide into a filament. Asexual reproduction may also take place through aplanospores and akinetes. Sexual reproduction is oogamous and macrandrous or nannandrous. The egg is produced in an enlarged gametangium known as the oogonium. The sperms come from a pair of short, box-like cells, the antheridium. Each antheridium usually produces 2 multiflagellate sperms. There are two types of oogamous reproduction. When the male filament is a few-celled dwarf epiphytic on the normal female filament, the species is said to be nannandrous. This is in contrast to the macrandrous species where the male filaments are the normal large type.
Bold, H. C., C. J. Alexopoulos & T. Delevoryas, 1987. Morphology of plants and fungi. Harper & Row, New York. (5th ed.). 912pp.