A strew slide of Pleurosigma intermedium. Some issues with the mountant. Prepared by John Thomas Norman. Olympus BHB microscope using 450nm LED light. As well as the wider field of view, I imaged one using the 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 9 images stacked in Zerene (Pmax). Quite low contrast – I’m assuming Canada Balsam for the mountant.
Pleurosigma intermedium W.Smith 1853. Published in: Smith, W. (1853). A synopsis of the British Diatomaceae; with remarks on their structure, function and distribution; and instructions for collecting and preserving specimens. The plates by Tuffen West. In two volumes. Vol. I. pp. [i]-xxxiii, 1-89, pls I-XXXI. London: John van Voorst, Paternoster Row. Page 64, Plate XXI [21], Figure 200. Homotypic synonyms: Gyrosigma intermedium (W.Smith) Griffith & Henfrey 1855, Pleurosigma nubecula var. intermedium (W.Smith) Cleve 1894. Heterotypic synonyms; Pleurosigma nubecula W.Smith 1853, Pleurosigma intermedium var. nubecula (W.Smith) Grunow ex Van Heurck 1896.