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.

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.

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.

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.

Most of the 60 species of Ulothrix occur in freshwater. They grow in ponds, rivers, streams, canals, rivers, etc. Stays attached to submerged objects. A few species are marine. They are not born in summer season. Professor A. K. M Nurul Islam (1969) discovered Ulothrix simplex from Bangladesh. It is an endemic algae of Bangladesh. Besides, Ulothrix tenerrima and Ulothrix variabilis are found in Bangladesh.

The word Ulothrix is formed from the Greek words Oulos meaning wool and thrix meaning thread. Ulothrix means woolly thread. Ulothrix is a filamentous filamentous alga. Its Kingdom Protoctista, Division Chlorophyta, Class Chlorophyceae, Class Ulotricales and Tribe Ulotricaceae.

Gymnodinium and Microcystis algae produce harmful toxins. This toxin is harmful to fish and livestock. Harmful toxins produced by Gonyaulax algae accumulate in fish bodies. Eating this fish causes people to become paralyzed.

Damages walls and buildings by causing algae growth. As a result the stability of the installation is lost.

Parasitic algae cover host plants and interfere with photosynthesis.

Some algae provide nourishment to mosquito larvae and help increase mosquito population.