A strew slide of Amphipleura lindheimeri (along with some other species) from Cuba. Prepared by Samuel Henry Meakin. Mounted in Sirax and dated December 1937. Also has ‘Test’ written on the label. Olympus BHB microscope using 450nm LED light.
I did something a bit different for the main images with this slide – I used a Reichert Neo 1.18/1.42 dark ground oil immersion condenser. With the 40x Leitz Pl Apo NA 1.00 objective (oil immersion), this produced a darkground image. A dark ground image with some rather blown out highlights (and this is a stacked image using Zerene, Pmax setting)….. Even with the image issues it does display the puncta and striae features, which is not bad for a NA 1.00 objective for this diatom. In theory, resolution with 450nm light for a NA 1.00 objective would be 225nm. The images were done with a 2.5x Nikon CF PL photoeyepiece and monochrome converted Nikon D850 camera.
Using the same condenser with a 63x Leitz Pl Apo NA 1.40 objective (oil immersion) produces a circular oblique lighting setup rather than dark ground, as the objective NA is so high. In the non-stacked images with this objective I measured the striae and puncta distances in ImageJ and got 324nm for the striae and 377nm for the puncta. Note, with this objective and 450nm light, theoretical resolution should be 161nm.