An arrangement of Plagiogramma hardmanianum (spelt hardmaniana on the slide). Edge view of valve and an angled side view. Described as ‘very rare’. No makers name, but based on the style, this is probably by Edmund Wheeler. 40x Leitz Pl Apo 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 80 images stacked in Zerene (Pmax). Given the small size of the coverslip ring, I couldn’t get close enough with the 63x objective I would have preferred to have used. So, 40x it was…. At some point black paint has been used around the coverslip ring, as the immersion oil brought a little of it off.
Original description of P. hardmanianum: Chase, H.H. (1885). Habirshaw’s Catalogue of the Diatomaceae . [Edition 3]. H.H. Chase, Geneva, New York, 1885., 343 + 11 (A-K) pp. Page 262. But no pictures in the online version I could find. While not this species, also see R. K. Greville; On plagiogramma, a new genus of Diatomaceæ. Quarterly Journal of Microscopical Science. 1 October 1859; s1-7 (28): 207–211. Plate 10. Screenshots of the plate and legend are shown above. The ones on this slide look a bit like Plagiogramma lyratum from Greville’s article (figure 14) however I cannot find another image of P. hardmanianum to compare mine with.