Filamentous algae are composed of cells that divide along a single plane, allowing only elongation to form filaments of one or more rows of cells. Algae that can divide in two planes can form sheet-like thalli or bodies.
Cells within filamentous algae divide along a single axis, enabling only elongation to form filaments with one or more rows of cells. Algae capable of dividing in multiple directions can create sheet-like structures or bodies.