Entogonia pulcherrima var. punctulata from Joe’s River, Barbados. Single example on the slide, mounted between two disc shaped diatoms. Mounted in Styrax. Date could be October 1933 (10/33 on the slide). Reference on the slide for Schmidt’s Atlas, Plate 203, Figure 15. Olympus BHB microscope using 450nm LED light. 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. 14 images stacked in Zerene (Pmax).
Also known as Entogonia punctulata Greville, 1863 and Triceratium pulcherrimum Greville, 1861. Original description: (of Entogonia punctulata Greville, 1863) Greville, R.K. (1863). Descriptions of new and rare Diatoms. Series X. Quarterly Journal of Microscopical Science, 2nd series. 3: 227-237, pls IX& X. page(s): p. 237; pl. 10, fig. 24
Oooh, this was a frustrating slide to image. It is bowed slightly, but the main issue is that the diatom is mounted very deep. This meant that I couldn’t use my 40x or 63x Leitz oil immersion objectives. The coverslip ring is even shaved down on the right hand slide, presumably because otherwise the objectives kept banging into it. I even worked through my array of objectives to find an alternative one to use with more working distance, but in the end I had to use the 20x Nikon Plan Apo NA 0.65. A nice objective lens, but the low magnification and relatively low NA means that detail is limited. I shall return to it if I manage to get a better objective to image it with.
EDIT, 2nd December 2024. I have sourced a 50x Nikon Plan Achromat NA 0.85-0.55 iris, oil immersion, objective. This has a longer working distance (0.34mm) than my 40x, 63x and 100x Leitz Pl Apo and I thought it would help with this diatom. It did help somewhat so I have added a new image, but I still couldn’t get deep enough to look all the way down the edges of it. Olympus BHB microscope using 450nm LED light. 50x Nikon Plan Achromat NA 0.85-0.50 objective (set to 0.85), oil immersion. Olympus Aplanat Achromat condenser, oblique lighting, oil immersion. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 24 images stacked in Zerene (Pmax).
EDIT, 4th December 2024. I’ve been on the lookout for a 50x Leitz Fluoreszenz NA 1.00 water immersion objective for a while, as this supposedly has a very large working distance (0.68mm!!). This is massive, especially for an objective with relatively high NA and magnification. To put it into context, the working distance for the Leitz Pl Apo objectives is about 0.18mm. Mistakes do happen in Leitz catalogues, and I was wondering if this was one of those, but I wasn’t able to find anyone who could confirm it for me. They are normally for sale for silly amounts of money, but a few days ago I managed to get one in the UK for a good price so I took a gamble and it arrived today. I can indeed confirm it has a very long working distance. So long in fact that when I originally set the stage to start my focusing, I was way to close. This long working distance will be very handy for deeply mounted diatoms, or those too close to a coverslip ring. The final image was OK, not up to the standard of a Pl Apo objective, but then I didn’t expect it to be. Similar to the Nikon Plan Achromat at NA 0.85, with perhaps a tough more resolution but a bit lower contrast. A very handy objective to have in case of emergencies. The extra working distance allowed me to get all the way to the bottom of the diatom, and I still wasn’t close to the coverslip. Olympus BHB microscope using 450nm LED light. 50x Leitz Fluoreszenz (an Achromat) NA 1.00 objective, water immersion. Olympus Aplanat Achromat condenser, oblique lighting, oil immersion. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 33 images stacked in Zerene (Pmax).