A strew of Asterionella sp. (I think Asterionella formosa) prepared by Northern Biological Supplies Ltd. Olympus BHB microscope using 450nm LED light. As well as the strew, I imaged one group 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. 7 images stacked in Zerene (Pmax).
Asterionella formosa Hassall, 1850. Published in: Hassall, A.H. (1850). A microscopic examination of the water supplied to the inhabitants of London and the suburban districts; illustrated by coloured plates, exhibiting the living animal and vegetable productions in Thames and other waters, as supplied by the several companies; with an examination, microscopic and general, of their sources of supply, as well as the Henly-on-Thames and Watford plans, etc. pp. 1-66 [advertisements pp. 67-69], pls I-VII. London: Samuel Highley, 32, Fleet Street. Pages 9,10, Plate II (Grand Junction Company), Figure 5 (p. 62).