Phylum: Charophyta   Family: Desmidiaceae

Cosmarium furcatospermum  West & G.S. West 1894

Recent survey work in the Outer Hebrides would suggest it is rather scarce. The few finds to date would suggest a circumneutral habitat is required, which is oligo-mesostrophic. West & West (1908, p. 206, pl.81: 10-11 & pl. 84: 8-10) liken it to C. sphalerostichum Nordstedt 1876 noting in particular the difference in the zygospores. However, there is some doubt as to the reliability of the spore depicted (see Kouwets in manuscript for more details).

References: 
West, W. & West, G.S. (1908) A Monograph of the British Desmidiaceae, Volume 3.
Kouwets, F.A.C. (in manuscript) European Flora of the Desmid Genus Cosmarium.