Desmids – an introduction

October 21st 2021

Desmids – an introduction

In recent years references to the freshwater green algae known as desmids have featured in a number of our articles. These have been based on drawings and lists prepared by an old friend, David Williamson, from samples collected by us.

David, now in his nineties, is one of few experts in this group worldwide. His interest in them extends to over sixty years.  An account of his Assynt finds may be found in a paper in the Botanical Journal for Scotland for 1996. This paper is available on our website.  In it he lists 291 taxa from some 79 sites.  Since 1996, he has added taxa to this list from many more local sites, and continues to do so.

There has been a new recruit to the ranks of British desmidologists in recent years, Chris Johnson, Chair of Curracag, the Outer Hebrides Natural History Society.  An article by him, entitled An introduction to desmids, lavishly illustrated with his photographs, appeared in the recent issue of the Hebridean Naturalist (20, 71-86), which was brought to our notice by David.  We thought that it might provide some interesting background to David’s records and, with Chris’s permission, it too is now available on our website.

More information on Chris’s work in this group may be found on his website Outer Hebrides Algae.

Four of Chris’s photographs from his website accompany this post and his recent article, An introduction to desmids, is available here.


Ian M. Evans

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Single bird hovering between road and waterfall, Clashnessie (Neil McCrimmon) (26/11)

Fieldfare and Redwing

A mixed flock of c30 fieldfare and c10 redwing in tall aspens, Nedd (Ian Evans). Mixed flock of 200+ birds over Culkein Drumbeg (DAH) (23/11)


Single bird by River Inver, Brackloch (Carol Langford) (22/11)


Single hen bird in back garden, Nedd (Ian Evans).  Rarely seen in this part of Assynt (21/11)

Great Northern Diver

Single bird, Bay of Stoer (John Gilbertson) (21/11)

Redwing and Fieldfare

c80 birds in a mixed flock flying over the B869 by Rhicarn (Richard Chappell and Ennis Jones) (20/11)


Single bird in tree overhanging river Inver, Little Assynt (Richard Chappell and Ennis Jones) (20/11)


Single bird hovering by roadside, Inchnadamph (Richard Chappell and Ennis Jones) (20/11)