Phylum: Charophyta   Family: Mesotaeniaceae

Netrium parvum (O. Borge) O.A. Petlovany 2015

First described and illustrated by Borge (1925: 14, pl. 1: 19) as Netrium digitus f. parvum. Shortly after Borge [in] Kreiger (1933: 216, pl. 8: 2) raised it to a variety. Petlovany [in] Tsarenko et al. (2015: 21) raised it to species level. Coesel & Meesters (2023: 24, pl. 4: 4-5) prefer to keep is as a variety but noting it is well distinguished from the nominate variety, indicating the status of a separate species. (A rather ambivalent position.) They also note, as indeed do Borge (1933: 216) and Petlovany (L.c.), that it’s remarkably similar to Gistl’s (1914: 13, pl. I: 7) Netrium conicum. If that proved to be the case, it would take priority.
Cell dimensions: L: 50-135 µm; B: (10-)22-35 µm, L/B: 2.0-4.5.
This taxon is rarely recorded in the Outer Hebrides but may have been confused with similar species. Found in circumneutral waters such as shallow moorland pools and loch-margins.

References: 
Borge, O. (1925).. Die von Dr. F.C. Hoehne während der Expedition Roosevelt-Rondon gesammelten Süsswasseralgen.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition).. Desmids of the Lowlands.
Gistl, R. (1914).. Beitrage zur Kenntnis der DesmidiaceenfIora der bayerischen Hochmoore.
Krieger, W. (1933).. Die Desmidiaceen Europas mit Berücksichtigung der aussereuropäischen Arten.
Tsarenko, P.M., Wasser, S.P. & Nevo, E., editors (2014).. Algae of Ukraine, Volume 4: Charophyta.