What you need to study spores under a microscope

The microscope

You need a compound microscope. It has an eyepiece and several objective lenses. Spores are small, so magnification matters.

The shop’s FAQ says that 400x to 1000x shows Psilocybe cubensis spores clearly. Scottish Fungi says 1000x gives the most detailed view on a compound microscope. The same guide says the x40 objective is the one used most for microscopic features.

Published texts usually quote the higher magnifications. Note the objective you used whenever you record a result.

Total magnification is the eyepiece power multiplied by the objective power. A 10x eyepiece with a 100x objective gives 1000x.

Light and oil immersion

At 1000x, the shop’s FAQ advises oil immersion. A drop of immersion oil on the slide cuts glare. The FAQ says oil immersion at this level gives the most structural detail.

Brightfield lighting is the usual setting. Use the same light for every sample you compare. Keep the stage steady.

Slides and cover slips

A slide is a flat piece of glass that carries the sample. A cover slip is a thin piece of glass laid over it. Use a small amount of water for the mount.

A correctly prepared slide has the liquid just meeting the edge of the cover slip all the way round.

Many objectives are made for a cover slip about 0.17 mm thick, called number 1.5. The figure is usually printed on the objective barrel. Check the thickness before you buy cover slips.

A calibration scale

A microscope image shows no scale of its own. You need two items to measure a spore.

• A graticule. This is a fine scale fitted inside an eyepiece. It is also called a reticle. It has no fixed length until you calibrate it.
• A stage micrometer. This is a slide with a ruled scale of known length. Its divisions are ten micrometres apart.

Nikon states that a calibration holds only for one objective and eyepiece pair. Calibrate each objective you use. The method is in the guide on how to measure a spore.

Why the scale matters

Spore size is one of the features mycologists use to separate species. A reading is only useful if someone else can repeat it. Calibration turns a count of graticule divisions into micrometres. Without it, two readings cannot be compared.

Calibrate once for each objective, and write the value on the record sheet. Check it again if you change the eyepiece.

A record sheet

A record sheet turns a look into a result. It can be a printed page or a spreadsheet. Give each sample its own row, with these columns:

• date and sample label
• objective and total magnification
• mounting liquid
• calibration value in micrometres per division
• spore length and width, one pair per spore
• notes on shape, colour, wall and germ pore

A camera adapter or phone clip lets you add a photograph to each row. Keep the sheet with the sample label. A later reading can then be compared with an earlier one.