Phylum: Charophyta   Family: Mesotaeniaceae

Netrium digitus var. rhomboideum R. Grönblad 1920

First described and illustrated by Grönblad (1920: 13, pl. 4: 38). Kossinskaja (1952: 84, pl. 10: 1-3) made this a forma [Netrium digitus f. rhomboideum] but it is generally regarded as a retrograde move and is widely ignored by most, if not all, later authors. Some cells are difficult to determine from the nominate variety and are best ignored. Var. rhomboideum is generally smaller, especially in terms of breadth; the L/B ratio is similar.
Cell dimensions: L: 146-182 µm; B: 46-70 µm, L/B: 2.4-3.2.
A relatively common and variable species, found in acidic habitats such as Sphagnum bogs.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Grönblad, R. (1920). Finnländische Desmidiaceen aus Keuru.
Kossinskaja, E.K. (1952). Flora sporovykh rasteniy SSSR. Kon"yugaty, ili Stseplyanki (1). Mezoteniyevyye i Gonatozigovyye Vodorosli [Non-Vascular flora of the USSR. Conjugates (I). Mesotaeniales and Gonatozygales].
Ohtani, S. (1990). A Taxonomic Revision of the Genus Netrium (Zygnematales, Chlorophyceae).