Phylum: Charophyta   Family: Desmidiaceae

Euastrum tumoriferum (E.K. Kossinskaja) M.C. van Westen & P.F.M. Coesel 2020

First described and illustrated by Kossinskaja (1936: 417, pl. 1: 10) as Euastrum binale f. tumoriferum. More recently, Van Westen & Coesel (2020: 112) though it sufficiently distinct to warrent species rank. Rather similar to Euastrum neogutwinskii – one of the main differences is the breadth of the apex in relation to the breadth of the semicell: no more that 60 percent in E. tumoriferum; over 65 percent in E. neogutwinskii.
Cell dimensions: L: 21-25 µm; B: 16-21 µm; Is: c.5 µm; Th: 11-12 µm; L/B: 1.3-1.4.
A rare desmid, found in acidic moorland pools and bogs. Status unknown in the Outer Hebrides due to confusion with similar species.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Kossinskaja, E.K. (1936). Desmidievye vodorosli iz Artiki (Desmidien der Arktis).
Van Westen, M.C. & Coesel, P.F.M. (2020). Taxonomic notes on desmids from the Netherlands III, with a description of five new species.