An arrangement of Nitzschia singalensis from Burma (now Myanmar). Spelt singalense on the slide. Mounted in Styrax. Prepared by Watson and Sons Ltd. Olympus BHB microscope using 450nm LED light. Arrangement was imaged using a 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 20 images stacked in Zerene (Pmax).
For the higher resolution image I originally used my trusty 63x Leitz Pl Apo NA 1.4 objective, with oblique light, but I couldn’t make out the striae. Not hugely surprising, as the slide label gives them as 120,000 per inch (212nm pitch)!! I therefore did an image (not a stack) using 365nm light, with a Lomo ОИ-14 condenser, oblique, oil immersion, and the 63x Leitz Pl Apo NA 1.4 objective, oil immersion, with the focus set to the best contrast for the striae. Measuring this in ImageJ gave me spacing of 223nm, which was pretty close to the 212nm on the slide (based on 25.4mm per inch). This is about the size of some of the smallest bacteria. Amazing that they were able to see these at the time of making the slide.
Nitzschia singalensis Spitta, 1920. Original description: Spitta, E.J. (1920). Microscopy: the construction, theory and use of the Microscope. 3rd Edition. John Murray, London. 534 pp. Page 393, Plate 22, Figures 1,3.