Phylum: Charaophyta   Family: Zygnemataceae

Zygnema C. Agardh, 1817

Cells of Zygnema are cylindrical and have two characteristic star-shaped chloroplasts. Each chloroplast has a pyrenoid. The filaments are unbranched and not very long. They may be attached to a substrate by means of rhizoids.
Cell dimensions: L: 35-60 µm; B: 16-35 µm.
Common in shallow waters where it can form luxuriant growths.

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition) The Freshwater Algal Flora of the British Isles.