Arnoldiella

Arnoldiella is a genus of green algae in the family Pithophoraceae. The genus name of Arnoldiella is in honour of Vladimir Mitrofanowitch (Mitrofanovich) Arnoldi (1871–1924), a Russian professor of biology.

Arnoldiella consists of a prostrate layer of coalescing filaments, from which arises a dense cushion of short, coarse, erect filaments. Cells of the prostrate layer contain one or several nuclei, while cells of the erect filaments are multinucleate. The erect filaments are uniseriate (one cell thick), and may have primary, secondary or tertiary branches. Cells of the erect filament are cylindrical, becoming shorter near the apex; each cell contains a parietal, net-like chloroplast with numerous pyrenoids. Apical cells may be rounded or pointed. The cell walls are thick and lamellated, at least for the cells near the basal parts.