Phylum: Charophyta   Family: Mesotaeniaceaea

Mesotaenium chlamydosporum A. de Bary 1858

First described and illustrated by De Bary (1858: 75, pl. 7D: 1-29). Mature cells are cylindrical but in any given population there will be numerous immature cells, which are slightly tapered and smaller. Cell content can be coloured purple to violet but this pigment is often lacking. The chloroplast in face-view only filling part of the cell. However, the purple sap content can fill the cell. The first image depicted here is similar to Van Westen’s Mesotaenium chlamydosporum morpha (2024: 88) but his cells are generally a little smaller.
Cell dimensions: L: 16.5-24 µm; B: 11-15 µm; L/B: 1.5.
Found in mucilaginous masses atmophytically on moss and other substrates. Supposedly common but not well documented in the Outer Hebrides.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition).. Desmids of the Lowlands.
De Bary, A. (1858).. Untersuchungen über die Familie der Conjugaten (Zygnemeen und Desmidieen) Ein Beitrag zur physiologischen und beschreibenden Botanik.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1904).. A Monograph of the British Desmidiaceae, Volume 1.