Microspora species are unbranched filamentous green algae. There is a single dense net-like chloroplast, usually filling the cell, no pyrenoid. The cells are frequently rather bulbous or barrel-shaped, but the chief diagnostic character is the presence of H-shaped wall sections (only Tribonema shares this characteristic), which can usually be seen in the filament by careful focussing under favourable lighting (condenser iris shut down), and may be most clearly seen at the ends of filaments. When the filament degenerates they are frequently found free. The cell wall may be thin, with the H pieces readily visible overlapping each other slightly, or it may be thick and rather gelatinous in appearance, in which condition it may be diffcult to distinguish from Binuclearia.