Microscopic examination
When one is more experienced with fungi it will be found necessary to carry out many microscopic observations, but when commencing the study it is necessary only to have an ordinary microscope; a calibrated eyepiece-micrometer is an advantage as is an oil-immersion lens. An examination of the spores is always necessary; the examination of features such as the sterile cells on the gill and stem, etc., varies with the fungus under observation. Spores should if at all possible be taken from a spore-print and mounted on a microscope slide, either in water or in a dilute aqueous solution of household ammonia. Although for mycologists it is often necessary to measure spores to within a 1⁄2 micron (µm) this book has been so arranged that one only really has to distinguish between a spore which is small (up to 5 µm), medium (5-10 µm), long (10-15 µm), or large if globose and very long (if over 15 µm); this is not strictly accurate, but serves the purpose for an introductory text. It is important to describe the character of the spore, i.e. ornamentations, whether a hole (germ-pore) is present at one end and/or a beak (apiculus) at the other ([fig. 5]). With white or pale coloured spores it is useful to stain either the spore or the surrounding liquid with a dye—10% cotton blue solution is admirable, or a solution of 1·5 g iodine in 100 ml of an aqueous mixture containing 5 g of potassium iodine and 100 g of chloral hydrate. Both these dyes must be accurately made up if the study of the fungi is to be taken at all seriously; because some of the chemicals used above are not normally required by students, a chemist must make up the reagents for you. Often the spores turn entirely or partially blue-black or pale blue or purplish red in the iodine solution—a useful character.
![[Larger illustration]](#467779198995390083_illo013lg.png.id-2885982028108051162.wrap-0.html.html){kind=link}
Fig. 1. Dissection of a toadstool as recommended by the author. For explanation see text.
Material in good condition is always required and one of the first things the student needs to do is train himself to collect sufficient material in good condition. The steps by which all the structures of the fungus used in the text can be observed are outlined below:—
[Fig. 1] shows the cuts required to furnish suitable sections in order to observe the various structures and patterns of tissue which are important.
1. Carefully place the longitudinal section (AB) of the fruit-body which has been sketched gill-face down under a low power or dissecting microscope. Hairs or gluten on the cap, if present, will be made visible by focusing up and down ([figs. 2] and [3]A) and/or those on the stem ([fig. 3]B). When any part of the cut fruit-body is not being examined retain it in a chamber containing damp paper or moist moss; this will assist the cells to retain their turgidity, for they frequently collapse on drying and are difficult to observe except after performing often lengthy and special techniques.
If only one fruit-body is available, then cut along CD and mount in a tin box on a slide in order to obtain a spore-print (otherwise see [paragraph 6]).
2. Cut off a complete gill (E) and quickly mount on a dry slide. Under the low power of a microscope, the cystidia on the gill-margin will be visible ([fig. 4]); it will be seen whether the spores are arranged in a particular pattern ([fig. 5]) and whether the basidia are 2-spored or 4-spored. In white-spored toadstools it is difficult sometimes to determine whether the basidia are 2- or 4-spored so one must confirm the observations by other techniques.