Using a Microscope: Equipment

by Michael Kuo

What kind of microscope do I need, and where do I get it?

You'll need a pretty good microscope. The many microscopes in people's basements and closets--forgotten gifts to 12-year-olds whose enthusiasm dwindled a few weeks after Christmas--are usually toys, great for looking at hair follicles and the like, but usually not powerful enough to help you identify mushrooms. Some of the larger microscopic structures of mushrooms can sometimes be seen with these "Garage-Sale Microscopes," however, and if you'd like to whet your appetite I recommend trying to view the asci and spores of Morels by slicing a thin section of the spore-bearing surface (see this page for help) and using a tap-water mount (equipment required: garage-sale microscope; slide; cover slip; sharp razor blade; tap water; morel).

But if you want to go beyond having a little fun just seeing some or the larger microscopic features of mushrooms, you will need a microscope with an oil immersion lens, capable of magnifying things about 1,000 times--and the eyepiece of the microscope will need to have an ocular micrometer in it so that you can measure things. You will want an electric light source, controls to move the stage (the platform that holds the slide) mechanically, and a fine-focus knob (not just a single, coarse-focus knob).

You could buy a new microscope, of course. Just now, I spent 20 minutes on the Internet at microscope retailers' sites and could not find a new microscope with an oil immersion lens for less than $1,000.00. However, a used microscope will work perfectly well, assuming it's in good condition. You might want to try e-Bay, but I suspect that your best bet is to contact someone in one of the life science departments at a local university or community college. Former Biology 101 microscopes are not too hard to get hold of, and are often dirt-cheap in comparison to new equipment.

For more information on choosing a microscope, see Shelly Evans's "Choosing Your First Microscope" (2000; Field Mycology 1: 52).

Here I will explain the concept only; the step-by-step can be found with a little research on the Internet or in the sources by Smith, Smith & Weber on the Using a Microscope page.

The little ruler in the eyepiece of your microscope is divided up evenly into units--but those units do not necessarily correspond to anything in particular. You will need to compare the units on your microscope to the units on a special slide (called a "stage micrometer") that has known values on it. Most microscopic mushroom measurements are expressed in "micrometers," also called "microns." One micrometer is equal to 0.001 millimeter; the symbol for a micrometer is µ.

"Calibrating" your microscope is simply the process of comparing your yard-stick's units to the predetermined units on a special slide. Borrow the stage micrometer slide, if possible; you won't need to calibrate your microscope more than once. Once you have a conversion basis, you will need to do a little math every time you measure something. On my microscope, for example, each unit on my yardstick equals 1.07 µ when I'm using the highest magnification--which means that if I'm viewing something 10 units long, it's 10.7 µ (roughly 11 µ) long.

What other equipment will I need?

The obvious microscope things: slides, cover slips, extra bulbs, lens paper, and immersion oil. You will also need some very sharp razor blades, and some chemicals (see the next section).

Slides and cover slips are available from many sources. If you are an online shopper, try one of the many scientific equipment sites on the Internet. I use Fisher Scientific. Your experience and preferences will dictate what kind of slides and cover slips you need. Glass cover slips are wonderful, but expensive and easily broken. I use them (carefully) when I really need a good look at something like the gill tissue of a Hygrocybe; otherwise I use plastic, disposable cover slips, which are much cheaper.

You will need lens paper to clean your oil immersion lens after each use. Fisher Scientific is one of many online suppliers; also try your local camera shop, or your optometrist. Immersion oil can be purchased at Fisher Scientific, as well.

• KOH - Potassium hydroxide in a 3-5 percent aqueous solution that you will frequently use as a mounting medium (often in combination with a stain like phloxine, below). Consult your pharmacist for help in obtaining this chemical, or ask the mycologist at a local university (be nice!). Chemistry departments often stock KOH, as well. KOH is also used to determine (macro) Chemical Reactions of mushrooms, so you will be killing two birds with one stone.
  
  
• Phloxine - A red stain, particularly good for making hyphal (cellular) structures more visible. Ask a local biology teacher for help obtaining phloxine--or purchase it online at a scientific equipment site like Fisher Scientific.
  
  
• Melzer's Reagent - This chemical is an absolute must, and it is unfortunately extremely difficult to obtain. It contains water, iodine, and potassium iodide, all of which are fairly easy to get hold of--but it also contains chloral hydrate, which is a controlled substance. Thus, you won't be able to buy it online at a scientific equipment site. Virtually your only option is to beg it from a professional mycologist. Offer to pay for it. If she refuses your money, find out what kind of toner cartridge the Biology Department printer requires and donate one to the office. Even mycologists have difficulty obtaining Melzer's, however, and if the mycologist you know can't afford to provide you with some of her precious supply (or if you cannot find a mycologist), your last resort is to try explaining your situation to your doctor and getting a prescription for chloral hydrate (not likely; it's a date-rape drug) or for Melzer's Reagent itself, which a pharmacist could mix according to the formula below, which your doctor would need to write on the prescription (still not very likely, but not unheard of).
  
  Water: 22.0 gm
  Chloral hydrate: 20.0 gm
  Iodine crystals: .5 gm
  Potassium iodide (KI): 1.5 gm