How to view mushroom spores under a microscope: slide prep, magnification and what to record

01What you need

• A compound microscope with 10x, 40x and ideally 100x oil objectives (400x and 1000x total).
• Clean slides and coverslips, lens tissue, and immersion oil if you have a 100x objective.
• A spore syringe, print or swab from a named strain.
• An eyepiece graticule or a stage micrometer if you want to measure.
• A notebook. The specimen is only as useful as the record you keep of it.

02Preparing the wet mount

1. Shake the syringe gently so the spores are evenly suspended.
2. Place one small drop in the centre of the slide. Too much liquid floats the coverslip and everything drifts.
3. Lower the coverslip from one edge at an angle so the drop spreads without trapping air.
4. Blot any excess at the edge with lens tissue.
5. For a print, lift a few spores with a sterile blade into a drop of water first; for a swab, roll it through the drop.

If the field is too dense to see individual spores, dilute: a drop of the suspension into a drop of clean water on a second slide.

03Finding and focusing

Start at 100x to locate spores, which look like tiny dark ellipses. Move to 400x and fine focus: this is the working magnification for shape and size. At 1000x with oil the spore wall resolves as a distinct band and the germ pore becomes visible as a small flattened area at one end. Close the condenser diaphragm a little for contrast; spores are nearly transparent individually, and it is the wall that gives them definition.

Albino and leucistic lines are a good exercise in contrast because their spores are almost colourless. Lower the light and use the diaphragm rather than turning up brightness.

04Measuring

Calibrate the eyepiece graticule against a stage micrometer once per objective and write the factor down. Then measure twenty spores, not two, and record the range: Psilocybe cubensis typically falls around 11 to 17 by 7 to 10 micrometres, subellipsoid, thick-walled. A single measurement means little; a range from a named LOT means a great deal.

05What to record

Strain, LOT number, date, objective, the size range, shape, wall thickness, germ pore, colour in mass from the print if you have it, and a photograph through the eyepiece if you can manage one. Do it the same way every time and your notebook becomes a reference library of its own. Our magnification guide and the spore morphology notes will fill in the detail.