A RARE FORM OF A BEAUTIFUL DESMID

by William Ells


'This beautiful desmid is a distinctly "Western type" and is more frequent in the plankton than other situations, often occurring in abundance' West & Carter (1923). I have only ever found a few cells of this very attractive single celled freshwater plant. All from three sites in Sutherland, Scotland.

The specimen figured is Staurastrum brasiliense var. lundellii W.&.G.S.West 1896. This is usually five angled rarely six (In British waters). The type Staurastrum brasiliense Nordst 1869, which is usually four angled, sometimes five, and only a little more than half the size of the variety lundellii, was not recorded from the British Isles by W.&.G.S.West and is not in The British Check-List (1991). The above described as a variety by West & Carter is in the list as a 'facies'. The species cannot possibly be confused with any other ( that's how I like 'em ). All the specimens from Scotland the five & six angled have straight spines, the centre ones at each angle being slightly longer than figured by West & Carter, they were out of focus in my drawing at (a) and are indicated by dotted lines, side view (b) and detail shown at (c). Lind & Brook (1980) show the Lake District specimen with the shorter straight centre spine, and the two outer spines at each angle are shown slightly curved.

This article first appeared in issue No.30 of Balsam Post the newsletter of The Postal Microscopical Society (British).
 
 
 
 

When I collect or receive samples, about half the sample is preserved the rest being examined live. I prefer examining living material, preserving in NBS * Algae Fix No.1 & 2 will help keep desmids green, but there is nothing like the bright often vibrant green of living specimens. Beginners who have only seen desmids in fluid mounts on the PMS Circuit are strongly advised to collect fresh samples from Loch, Lake and Tarn, boggy places where sphagnum moss and the Sundew plant grows are ideal places to find desmids.

 * NBS = Northern Biological Supplies, 3 Betts Avenue, Martlesham Heath, Ipswich IP5 7HR, England.

References:-

Brook A.J. & Williamson D.B. (1991). A Check-List of Desmids of The British Isles. Freshwater Biological Association.

 Lind E.M. & Brook A.J.(1980). Desmids of the English Lake District. Freshwater Biological Association.

 West W. & West G.S. Vol 5 by Nellie Carter 1923. A Monograph of the British Desmidiaceae. Ray Society.


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