An Uncommon British Desmid,
Staurastrum monticulosum Brebisson (1839) var. monticulosum.

William Ells
Coniferae, Walnut Tree Lane, Loose, Maidstone, Kent. ME15 9RG. UK.

The specimens of St. monticulosum examined correspond with Nellie Carter's (1923) original figures of the typical form from Loch Luichart, Ross, Scotland. With the exception in some specimens, there is a smaller third spine which can be seen at the angles of the triangle in vertical view and the lateral angles in face view. The species occurs quite frequently in the sample collected this year (1997) although it was not seen in a sample collected from the same boggy area in 1993. See the scanning electron microscope photomicrograph and figures below.

Carter (ibid) gives a number of sites throughout Britain where according to W.&.G.S.West the typical form of St. monticulosum can be found, however she states :-

'Typical St. monticulosum is not a common desmid in the British Isles, var. bifarium Nordst. (1873) being much more frequently found. Apparently W.&.G.S.West did not thoroughly understand this species, for Pl. CLIV, fig. 11. is a drawing showing their idea of the typical form. This obviously does not belong to St. monticulosum, and the localities for the species with the West's authority (shown!) should consequently not be taken as correct.....'

Carter (ibid) shows three varieties two of which are described as being very similar, and the third not being correctly placed in St. monticulosum according to Gronblad (1920). Prescott et al.(1982) show no less than twelve varieties none of which appear to match precisely the figure by Carter.

The conclusion from the above, taken together with the fact that to-date the author has only seen it from one habitat in north west Scotland and Nellie Carter describes it from only one other Scottish locality, is that this typical form is somewhat rare in Britain.

The author will be pleased to hear if anyone else has found the type species, particularly in British habitats.

References:-

Carter Nellie (1923) A Monograph of the British Desmidiaceae by W.&.G.S.West, Vol. V by Nellie Carter. Ray Society, London, England.

Prescott G.W., Bicudo Carlos E. & Vinyard W.C. (1982) A Synopsis of North American Desmids. University of Nebraska Press.

Acknowledgements:-

Grateful thanks to Mr. Alan Joyce for providing the samples from an acid bog in North West Scotland and to Mr. Andrew Syred for providing the SEM image.

Figures:-




Figure 1. Face view of Staurastrum monticulosum (specimen 1).













Figure 2. (a) Face view and
(b) end or apical view of Staurastrum monticulosum (specimen 2).











Figure 3. SEM of Staurastrum monticulosum.


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First published in Micscape Magazine, November 1997 ( ISSN 1365 - 070x )

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