D. THE STOMACH FUNGI
The Gasteromycetes are a complex mixture of higher fungi united in virtue of their spores being enclosed in a fruit-body and not forcibly ejected from the basidium; the group includes the puff-balls and their relatives.
Key to some groups
- 1. Fruit-body growing beneath the surface of the soil (hypogeous) False truffles (including Hymenogaster, Rhizopogon)
- Fruit-body not growing beneath the soil-surface 2
- 2. Spores in a slimy mass on a specialised fruit-body arising from an egg-like structure Stinkhorns (Phallus & Mutinus)
- Spores powdery at maturity or in small capsules [3]
- 3. Spores powdery at maturity and contained within the fruit-body [4]
- Spores enclosed in a small capsule or group of capsules in a cup-like structure, resembling the eggs within the nest of a bird Bird’s nest fungi (including Crucibulum & Cyathus)
- 4. Spores intermixed with threads within the fruit-body from which they are dispersed through a specialised pore at its apex Puff-balls and Earth-stars (Lycoperdon & Geastrum)
- Spores not mixed with threads within the fruit-body and not dispersed through special structure but through cracks as the fruit-body weathers Earth-Balls (Scleroderma)
The Gasteromycetes is an unnatural group of predominantly saprophytic higher fungi many of which are extremely grotesque and strange in their morphology. Instead of the spores being formed asymmetrically on the basidium as is found in the agarics, the spores of members of this group are usually more or less symmetrically attached to their sterigmata or may even be seated directly (sessile) on the basidium. The whole group, even if unnatural, can, however, be regarded under one heading as a biological unit. Until something better is suggested and supported by evidence the existence of this group is very convenient.
Usually the basidia project into cavities within the fruit-body in which the spores themselves are released as the fruit-body gradually matures—hence the name Gastero-mycetes: ‘stomach-fungi’. In a few more advanced forms, the puff-balls of temperate countries, for instance, the spores escape from these cavities through a pore or pores in the outer wall of the fruit-body, and in the stinkhorns the spores are exposed as a sticky mass because the smell of the material in which they are held is attractive to flies. In forms which have subterranean (or hypogeous [p. 243]) fruit-bodies there is no special opening and here the spores are dispersed by insects and small mammals. In the bird’s nest fungi the spores are enclosed in separate packets within a saucer or cup-like open structure.
Recently it has been shown by examination of the microscopic structure of the fruit-bodies and spores that certain genera of the Gasteromycetes are more closely related to the agarics than many of them are between themselves.
It is believed that some of the Gasteromycetes may have evolved from more familiar fungi by adaptation to arid or semi-arid conditions. Although this is not true for all the Gasteromycetes within this one group of fungi, a whole series of methods of overcoming the disadvantages connected with non-violent disposal of spores has evolved. These methods include both changes in structure and ecology; only a few have evolved a mycorrhizal relationship with higher plants.