Phylum: Charopyta   Family: Mesotaeniacea

Netrium naegelii (L.A. de Brébisson ex W. Archer) W. & G.S. West 1904

First described by Brébisson ex Archer [in] Pritchard (1861: 751) without illustration. It was later moved to its current genus by West & West (1904: 66, pl. 7: 4-5) and illustrated. They note: “This species bears considerable resemblance to N. digitus, but is of smaller size and somewhat narrower. It is a very uncommon plant in the British Islands and we have not seen many specimens of it.” The zygospore depicted below is the first time it has been found in the natural environment. It was with a good population of vegetative cells and the apices on the gametangial cells match those on the live cells.
Cell dimensions: L: 115-175 µm; B: 25-42 µm; L/B: 4-5.
Zygospore dimensions: 62 x 50 µm (not quite mature).
A rare taxon found in moorland pools, abandoned peat-cutting and also from moss on wet rocks.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Ohtani, S. (1990). A Taxonomic Revision of the Genus Netrium (Zygnematales, Chlorophyceae).
Pritchard, A. (1871). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign.
Ralfs, J. (1848). The British Desmidieae.
West, W. & West, G.S. (1904). A Monograph of the British Desmidiaceae, Volume 1.