Hyalotheca

Hyalotheca is a genus of green algae, specifically of the Desmidiaceae. It has a cosmopolitan distribution and is found in acidic, oligotrophic freshwater habitats.

Hyalotheca consists of chains of cells joined end-to-end to form filaments, which are surrounded in a thin or thick layer of mucilage. Cells are cylindrical with two identical halves called semicells; the isthmus (where the two semicells join) may be slightly constricted. Some species may have small protuberances near the cell median, making the cells appear somewhat lemon-shaped or triangular in apical view. The cell wall is smooth or with a transverse row of pores. Each semicell has one axial chloroplast, which is stellate in end view, with a central pyrenoid. The nucleus is located in the center of the cell, between the chloroplasts.