Part 3

Mount on a dry slide with the plane through PQ face down on the slide and observe under a low magnification, to assess whether cystidia on the gill-face are present or absent, and if present their general shape and whether numerous or infrequent (fig. 8).

Mount in water/washing-up mixture as outlined above and tap gently with the rubber attached to the end of a pencil; evenly distributed pressure should be given. If the gills appear to be too close then rotate the rubber a little whilst pressing in order to spread the tissue.

4. Using a low power of a microscope and looking down into the plane RS of the unmodified block M or a similar block, one obtains by this simple technique a very accurate idea as to the structure of the trama of the gill (fig. 9). The organisation of this tissue is very important in classification, some groups of toadstools having what has been described as regular trama (fig. 9C), others irregular (fig. 9D), inverse (fig. 9B) or divergent (fig. 9A). This same tissue may be thick or sparse to wanting, coloured or not. Such sections are often better than attempts at very thin sections unless very specialised techniques are used. There are few satisfactory thicknesses between the two extremes; the thick sections you can do and the very thin requiring expert techniques.

Fig. 8.

Fig. 9.

Fig. 10.]

5. Take out a small block of tissue T as indicated in the figure (fig. 1). Mount immediately and repeat as in 3. This will allow the outer layer of the cap to be more clearly seen (fig. 7A-C) and also the structure of the flesh (fig. 10). The latter may be composed of a mixture of filaments and ‘packets’ or ‘nests’ of rounded cells (i.e. heteromerous), or of filaments, only some of which may be inflated (i.e. homoiomerous); but when individual cells are swollen they never form distinct groups. By very similar techniques it is possible to show that the more woody fungi can have flesh composed of one of four types of cells (Corner, 1932): these types depend on whether distinctly thickened cells (plate 47) are present with the actively growing hyphae or not (pp. 140-150), whether hyphae are present which bind groups of hyphae together, etc. (plate 46).

6. Remove stem along line CD and cut out small blocks of tissue as indicated (U, V and W). Mount immediately and examine as in paragraph 3, for cystidia, etc. (see fig. 3).

Whilst all these sections are being cut and processed a second fruit-body, if available, should be set to drop spores; this is done by cutting off the cap from the stem and placing it either entirely or in part, and with gill-edges down, on a slide in a tin.

7. Z is a ‘scalp’ of a cap; a thin sliver from the cap is placed on a slide in a drop of water (modified with washing-up liquid, etc. as above). After placing a cover-slip over the tissue it is tapped gently; this will show if the cap is composed of globose to elliptic elements or if it is composed of strictly filamentous units (figs. 6A & B). Care must be taken not to reverse the section when transferring it to the mountant, either by turning the scalpel or by allowing the surface tension of the liquid to pull the section upside down. The construction of any veil fragments will also be seen in this mount, and if a loose covering of veil is present this should be removed before observation so that it does not obscure the fundamental structures.

8. Examine the stipe of the fruit-body used above under a low power or with a dissecting microscope in order to ascertain whether there are any remains of veil and/or vegetative mycelium. If found, mount immediately in the solution containing iodine mentioned above and examine.

Of course it is difficult to carry out the above system the first time and be successful in seeing everything, indeed in being able to cut all the sections 1-8. Practice makes perfect, so why not practise with a ¼ lb of mushrooms from the grocer before the autumn season starts. In this way you will have overcome the difficulties without having to experiment with your collections.

CHARACTERISTICS FOR THE IDENTIFICATION OF HIGHER FUNGI WITH CAPS Locality G. Ref. Date Habitat notes soil type pH vegetational community solitary; in troops or rings Draw or preferably paint exterior and vertical section of fruit-body MACROSCOPIC CHARACTERS CAP General characters: diameter shape consistency colour: when immature when mature when wet when dry Surface dry, moist, greasy, viscid, glutinous, peeling easily or not, smooth, matt, polished, irregularly roughened, downy, velvety, scaly, shaggy Margin regular, wavy incurved or not smooth, rough, furrowed striate or not Veil, if present colour abundance or scarcity distribution at margin, whether appendiculate or dentate consistency, whether filamentous, membranous GILLS, or pores or teeth etc. remote, free, adnate, adnexed, emarginate, subdecurrent, decurrent crowded or distant distinctly formed or not shape interveined or not easily separable from the cap-tissue or not consistency (whether brittle, pliable, fleshy or waxy) thickness width colour: when immature at maturity number of different lengths or number of layers obvious features of gill-edge, tube-edge, e.g. colour, consistency STEM central, eccentric or lacking shape dimensions: length thickness hollow or not colour: when immature when mature consistency (whether fleshy, stringy, cartilaginous, leathery or woody) surface characters (whether fibrillose, dry, viscid, scaly or smooth) characters of stem-base Veil, if present characters Volva, if present characters Ring, if present whether single or double whether membranous or filamentous whether persistent, fugacious or mobile whether thick or thin whether apical, median or basal FLESH colour in cap: when wet when dry colour in stem: when wet when dry colour changes if any when exposed to air presence or absence of milk-like or coloured fluid (note: colour when exuded on fruit-body immediately and after some time and when dabbed on to a clean cloth or paper handkerchief and exposed to the air). SMELL before and after cutting --relate to a common every day odour MICROSCOPIC CHARACTERS BASIDIOSPORES colour in mass colour under microscope. shape size type of ornamentation, if any size and shape of germ-pore, if present iodine reaction of spore-mass:--blue-black to dark violet (amyloid); red-purple (dextrinoid); yellow-brown or brown (non-amyloid) BASIDIA number of sterigmata CAP-FLESH type of constituent cells GILL-TISSUE type and arrangement of cells between adjacent hymenial faces CAP-SURFACE type of cells composing the outermost layer--whether filaments or rounded cells STERILE CELLS--CYSTIDIA presence or absence of sterile cells:-- on gill-edge on gill-margin on cap on stem shape, estimation of size, thick or thin-walled, hyaline or not types of ornamentation, etc.

Key to the major classes of Larger Fungi

Spores borne externally on stalks on a clavate to cylindrical cell Basidiomycotina Spores produced within a clavate, cylindrical or subglobose cell Ascomycotina

Key to major groups based on character of basidium and fruit-body shape

1. Basidia either produced in a hymenium or in a mass, and until maturity contained within a closed fruit-body Gasteromycetes

Basidia produced in a layer of cells (hymenium) and exposed to the air before the maturity of the spores (Hymenomycetes) 2

2. Basidia simple, a single cell (fig. 5) (Homobasidiae) 3

Basidia usually septate, or if simple then fruit-body gelatinous and often collapsing to form a skin when dried (Heterobasidiae) 4

3. Fruit-body usually fleshy, soft and easily decaying (putrescent), hymenium spread over the surface of gills, ridges or within tubes Agaricales (p. 22)

Fruit-body with hymenium smooth or spread-out on teeth, ridges or plates or if within tubes then fruit-body tough and leathery Aphyllophorales (p. 135)

4. Basidia divided 5

Basidia simple and apex drawn out into two long necks Plate 61 (p. 185) Dacrymycetales (p. 180)

5. Basidia divided transversely by one to three horizontal septae Plate 60 (p. 183) Auriculariales (p. 182)

Basidia divided into two or four cells by vertical septae Plate 61 (p. 185) Tremellales (p. 184)

A. AGARICS AND THEIR RELATIVES

Key to major genera