I’m working on an Aspicilia and these objects appeared after KOH was added to an apothecia section. The yellow circled one is 37.5 X 10 microns, the long ones are 50 X 5 microns. Does anyone know what these are.

I would suggest looking at these with polarizing filters. They may be crystals of something, perhaps a lichen substance, perhaps not, but if crystalline they will be bright against a dark background with crossed polarizing filters. A number of lichen substances make boat-shaped crystals, but I would expect those to be soluble in K.

Hi all,

For what it's worth, I shared this photo and the text with a diatom specialist friend of mine, who replied: "Definitely diatoms".