Vegetative cellAn ordinary cell of the filament. The cells sit end to end in one row, with no branches.
HoldfastThe cell at the base of the filament. It fastens the filament to a surface.
CapsRings stacked at one end of a cell. Each one marks a time the cell has divided.
Cell wallThe firm wall round each cell, built partly of cellulose.
ChloroplastOne large chloroplast shaped like a net. It lies just inside the wall, all round the cell.
PyrenoidsSmall round bodies in the chloroplast. A cell has one or several.
NucleusOne large nucleus near the middle of the cell.
New filaments 5
OogoniumA swollen cell that holds one egg. A small opening in its wall lets a sperm in.
EggOne large egg inside the oogonium. It is packed with stored food and cannot swim.
AntheridiaA row of short, flat cells. Each one makes one or two sperm.
Dwarf maleA tiny male filament of only a few cells. It grows fixed to the larger filament, beside an oogonium.
ZoosporeA swimming cell that settles and grows into a new filament. A ring of flagella circles its clear front end.
How this list was compiled: Every name was checked on 2026-10-03 and kept only where two independent sources use it for Oedogonium. (1) Wikipedia, text only: Oedogonium, https://en.wikipedia.org/wiki/Oedogonium . (2) G. S. West, A Treatise on the British Freshwater Algae (1904), the Oedogoniaceae, public domain, https://archive.org/details/treatiseonbritis00west . (3) J. Y. Bergen and B. M. Davis, Principles of Botany (1906), public domain, https://archive.org/details/principlesofbota00berg . (4) J. M. Coulter, C. R. Barnes and H. C. Cowles, A Textbook of Botany, volume 1 (1910), public domain, https://archive.org/details/textbookofbotany01couluoft . Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. Licence: own work
How it works
Oedogonium is a green alga that grows as unbranched filaments in fresh water. The filament shows its cells, one enlarged. New filaments shows the oogonium, the antheridia, a dwarf male and a zoospore.
Read the full guide
The filament
The holdfast is the cell at the base. After it the vegetative cells sit end to end. Caps are the rings at one end of a cell that has divided. In the enlarged cell the chloroplast is a net just inside the cell wall, with pyrenoids on it and the nucleus near the middle.
New filaments
An oogonium is a swollen cell with one egg inside. Antheridia are short cells in a row. A dwarf male is a tiny filament fixed beside an oogonium. A zoospore swims with a ring of flagella.
Questions and answers
What is Oedogonium?
A green alga of fresh water that grows as fine, unbranched filaments. Each filament is one row of cells joined end to end. It may be fixed to a surface by a holdfast cell at its base or float free.
What are the caps on an Oedogonium cell?
Rings stacked at one end of some cells. A new ring is added each time the cell divides, so the number of caps shows how many times that cell has divided.
What shape is the chloroplast of Oedogonium?
A net. Each cell has one large chloroplast whose strands join into a network just inside the wall, with one or several pyrenoids on it.
What is a dwarf male in Oedogonium?
In some species the male filament is tiny, only a few cells long. It grows from a small swimming spore that settles on the female filament, on or beside an oogonium, and its end cells are antheridia.
How does Oedogonium reproduce?
A vegetative cell can release a zoospore, which swims with a ring of flagella, settles and grows into a new filament. In sexual reproduction a sperm enters an oogonium and joins the egg, which becomes a thick-walled oospore.