Ulothrix is a sessile, endlessly growing alga with linear filaments. Its physical structure can be described in two ways. Filament structure and cell structure.
Structure of Ulothrix filaments
Ulothrix is a green multicellular alga. Many cells are joined end to end to form slender, linear and unbranched filaments. Its filaments are composed of three types of cells. These are-
1. Hold fast: The thin, long and colorless cells at the base of algae are called hold fast or hepteron. This keeps the algae attached to the soil or other objects.
2. Somatic cell: Ulothrix is a multicellular algae. Its body is made up of small unicellular cells. The cells look the same. Cells may be of greater width than length or of equal length and width. Body cell length 2-6 times greater than width depending on the species. Physiological growth of algae occurs due to the increase in the number of body cells. Hence its physical growth is indeterminate. Cells are green and produce food through photosynthesis.
3. Apical cell: There is a semicircular cell at the tip of the filament. The surface of the cell is cylindrical or spherical or like a convex lens. It is green and different from other cells.