(iv) Development of the agaric fruit-body

In the soil or substrate the hyphae of agarics frequently grow in close contact with each other, indeed the intertwining of such hyphae to form small knots is common in many fungi. In these intertwining hyphae, those close together divide and branch, later branching again to form a heap of tissue. The fruit-body develops from, or within, this knot and at its earliest stage is usually covered by loosely branched and irregularly arranged hyphae. To the unaided eye the primordium, for this is what such a structure or early beginning is called, appears to be enveloped in a mass of pale hyphal strands, often giving the fruit-body a woolly appearance when seated on the soil, wood, herbaceous debris, etc. If more than one primordium develops in close proximity, usually all but one abort early in development, or they remain checked in formation at this stage until those close by have matured. Some species which grow on wood are caespitose, that is clustered together, and in these cases all or many more of the primordia develop fully and simultaneously.

Often it is possible to search and find these primordia in the fields and woods, and if they are examined under the low-power of a microscope it is possible to study how the fruit-body subsequently develops from its small beginnings and the part played by the ring and volva in the development determined. Thus the origin of the veil can be located, its development followed as well as its disintegration. When the fungus is grown in pure culture on sterile dung, or soil, or wood, or simply on artificial media prepared in the laboratory the full sequence of events can be more easily followed. This is how the professional mycologist conducts his observations. By very careful studies it has been found in recent years that the development of the fruit-body, the origin of the gills, etc. can assist in the classification of the higher fungi. Thus some species have no protective tissue around the developing gills (gymnocarpic) whilst others have one or even two, simple or complex, tissues around the developing gills or pores (hemiangiocarpic). It is these tissues which give rise to the ring, volva, cortina, etc. This most exciting part of the study of the higher fungi is illustrated in the accompanying figures ([Figs. 12 & 13]) along with the various types of gill-attachment mentioned in the text ([Fig. 11 A-H]). If the agaric has two tissues surrounding it as the cap expands and matures, first the outer tissue or skin breaks leaving pieces on the stem and/or cap and then the second skin breaks as the cap expands still further. The last skin leaves remnants on the stem and sometimes bits and pieces at the cap margin. Only now can the agaric shed its spores from the fully exposed gills.

[Larger illustration]

(v) References

A. Reference Texts

Some references have already been given on [p. 264]. Findlay, Hvass & Hvass, Lange & Hora, Nicholson & Brightman, Wakefield and Dennis and Zeitlmayr.