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.

Lycoperdon pyriforme Persoon Stump puff-ball

Fruit-body: width 20-50 mm; height 40-75 mm.

Description:

Fruit-body: more or less pear-shaped, pale brownish often with a slight hump on the top, scurfy on the outside with tiny pointed granules which soon fall off or become rubbed off by abrasion, particularly after careless handling.

Stem: consisting of rather small cells and connected at the base by long, white, branched cords of mycelium which permeate the substrate.

Spore-mass: white at first then greenish yellow and finally olive-brown and formed around a sterile column.

Spores: small, olive, minutely warted but appearing smooth under the student microscope; 4 µm in diameter and intermixed with long, olive coloured, branched hyphal threads 4-5 µm broad and of irregular wall thickness.

Habitat & Distribution: This puff-ball grows in huge clusters on stumps and logs, or can be traced to buried pieces of wood; it occurs from summer to late autumn.

General Information: There are several species of Lycoperdon in this country, some quite small and several rather infrequent. L. pyriforme is the only one which grows on wood; ‘pyriforme’ means pear-shaped and is derived from the shape of the fruit-body.

L. perlatum Persoon

is also a common puff-ball; it is pestle-shaped or top-shaped, whitish or tan with minutely roughened, globose spores measuring 4 µm in diameter. The fruit-body is covered in a mixture of large and small, fragile spines which leave a network when rubbed off. It grows in woods and on heaths.

L. foetidum Bonorden

is similar to L. perlatum, but the spines are umber or vandyke-brown; it also grows both in woods and upland pastures, particularly the latter.

Illustrations: L. pyriforme—Hvass 316; LH 219; NB 155³; WD 109³. L. perlatum—Hvass 315; LH 217; NB 155²; WD 110².

Langermannia gigantea (Persoon) Rostkovius Giant puff-ball

Fruit-body: diameter 300-450 mm (-1,050 mm).

Description:

Fruit-body: round or slightly flattened on the top, smooth or cracked into small scales, white but becoming flushed yellowish with age and finally olive-brown when old, frequently the outer layer dries and breaks away to expose the powdery spore-mass within.

Stem: absent or only present as a small cone of tissue.

Spore-mass: whitish, cream-coloured and finally olive-brown.

Spores: small, brownish, minutely warted and spherical, 4-5 µm in diameter and intermixed with thick-walled, branched, brown hyphae, 3-5 µm broad.

Habitat & Distribution: On the ground in copses, at the edges of woods, under hedges or on refuse tips, and sometimes in gardens. It may appear in the same place year after year, and has been recorded growing beneath the rafters in houses.

General Information: When young it is white inside or cream-coloured before the spores have developed and can then be cut into slices and cooked. I have seen it on sale in markets in N. America and it is collected for food by many in Europe. Its pumpkin-shape with a circumference of anything up to 1,050 mm makes this fungus easily recognisable. The number of spores produced by a fruit-body measuring 400 × 280 mm has been calculated by A. H. R. Buller as 7,000,000,000,000 spores!

Calvatia utriformis (Fries) Jaap (= C. caelata (Persoon) Morgan)

has a goblet-like shape and a distinct, sterile base composed of large cells with a prominent membrane separating them from the spore-mass; the spores are 4-5 µm diameter, smooth and spherical.

C. excipuliformis (Fries) Perdeck (= C. saccata (Vahl.) Morgan)

is pestle-shaped with a well developed stem. The spore-mass is composed of warted, globose spores, 4-5 µm in diameter.

Bovista nigrescens Persoon

is very similar in shape to the Giant puff-ball, but is very much smaller; it lacks a stalk, being attached to the substrate only by mycelial cords. It commences white, but then darkens to become purplish brown at maturity when it also breaks from its moorings and rolls about in the wind.

The last three species are found on heaths, in pastures or on the ground in woods.

Illustrations: C. gigantea—Hvass 312; LH 217; NB 371; WD 109⁷. B. nigrescens—Hvass 311; LH 219; NB 37³.

Earth-stars and Earth-balls

The earth-stars, i.e. species of Geastrum, are closely related to the puff-balls, but differ in having two very distinct and separate enclosing walls, the outer one splitting at maturity to expose a ‘puff-ball’ within; an example of the genus is G. triplex Jungh, found in parks or under beech trees or G. rufescens Pers. (illustrated) in mixed woodland. The outer skin splits in different ways in different species: in some it splits like a star—hence the common name of Earth-star, in some the spore-mass is raised as if on stilts. There are several species of Geastrum recorded for Britain, but they are decidedly uncommon.

The Earth-balls are, however, far from uncommon and may be met with from early summer until late autumn in any wood particularly those on sandy soils. They are unrelated to the earth-stars.

Earth-balls

Scleroderma citrinum Persoon Common earth-ball

Fruit-body: diameter 25-75 mm.

Description:

Fruit-body: rounded or flattened on top, sometimes lobed, very firm, yellow or clay colour, scaly, thick, white within or pinkish, if cut when immature, and then purplish black as the spores mature.

Stem: absent or reduced to a small group of mycelial cords.

Spore-mass: purplish black.

Spores: medium to large, dark brown, 8-13 µm in diameter and covered with a delicate network.

Habitat & Distribution: On the ground in woods or on heaths.

General Information: This fungus is found in many books under the name of S. aurantium. S. verrucosum Persoon is closely related, but has a stem-like rooting base and an umber brown spore-mass. The spores are also slightly different; they are 10-14 µm in diameter and ornamented with spines and ridges.

The earth-balls appear to have characters in common with the false truffles, indeed sometimes they grow partially buried in the sandy soil of woods. Like the false truffles they have been used to adulterate pÂtÉ as a cheap substitute for true truffles (see p. 244). It is not wise, however, to eat earth-balls as there are cases of poisoning known. Although truffle-like, they should be avoided except under the guidance of an expert, as with agarics.

Illustrations: Geastrum triplex—Hvass 307; LH 221; NB 155¹. Scleroderma citrinum—Hvass 320; LH 223; NB 155⁵; WD 111³.

Stinkhorns

Phallus impudicus Persoon Common stinkhorn

Fruit-body: Egg: 30-60 mm in diameter—then Cap: 25-40 mm and Stem: width 18-25 mm; length 100-150 mm.

Description:

Fruit-body: commencing as a white, silky egg-like structure full of jelly in which is embedded a conical cap attached only at its apex to a cylindrical white, spongy, hollow stem.

Cap: covered in a slimy mass of dark olive-coloured spores at maturity.

Stem: cylindrical, rapidly elongating, white, spongy and hollow.

Spore-mass: dark olive-green, smelling strongly, foetid.

Spores: small, pale olive, oblong and 3-5 × 2 µm in size.

Habitat & Distribution: Common from summer to autumn on the ground in woods and in gardens.

General Information: Easily recognised by its shape and evil smell which can be detected at some distance. The unburst eggs are called ‘witches eggs’. Under favourable conditions the egg bursts and the stem elongates carrying the cap and spore-mass with it. The spore-mass is attractive to flies and they feed upon it; spores stick to their feet and so are transported from one place to another.

The very similar P. hadriani Persoon is frequently found in sand-dunes; it differs in having a lilaceous colour to the egg. An interesting variety of the common stinkhorn is uncommonly found and differs in having a skirt-like frill beneath the cap. The jelly in the egg is a water-store and is used by the fungus to expand rapidly.

Mutinus caninus (Persoon) Fries

, the ‘Dogs stinkhorn’, is found around old stumps or on piles of leaves. It has the spore-mass covering an orange-red pear-shaped cap which is itself fused to the stem.

The stinkhorns and their allies appear to be commoner in warmer countries where they take on many bizarre shapes. Other than the three species noted above stinkhorns are rarely found in this country, but when they are it would appear they have been introduced with foreign imports such as timber, ornamental plants, vegetables etc.

Eggs of phalloids brought into the laboratory can be surrounded by wet tissues or blotting paper and then allowed to develop further in a dish or box. Provided the skin covering the spores is not broken or injured the fungus will not smell and therefore before it becomes unpleasant, the whole mechanism of expansion can be studied.

Illustrations: Hvass 323; LH 215; NB 153¹; WD 108¹.

Birds nest fungi

Crucibulum laeve (de Candolle) Kambly

Fruit-body: diameter 8-12 mm.

Description:

Fruit-body: ochraceous brown or sand-colour, downy and then smooth, truncate, cup-shaped with the cup at first closed by a yellowish membrane which finally splits to expose a group of pale brown or dingy whitish, circular, lens-shaped ‘eggs’ (peridioles), scattered on a shiny pale ochraceous interior.

Spores: medium-sized, in packets within ‘eggs’, ellipsoid, hyaline, smooth and 8-10 × 4-6 µm in size.

Habitat & Distribution: Common in crowded groups on dead twigs, fern stems, straw and wheat stubble.

General Information: Cyathus differs from Crucibulum in the more complex fruit-body which consists of three layers, and the peridioles forming on distinct stalks. Two species are frequently seen: Cyathus striatus Persoon has a grey, fluted inner surface to the cup and strongly hairy red-brown outer surface; the spores measure 16-22 × 9-10 µm. Cyathus olla Persoon has a smooth, shiny, grey surface and minutely silky, yellowish grey outer surface. C. striatus is found on twigs, and about dead stumps; C. olla is more frequent in gardens on herbaceous debris and dead pieces of perennial flowers—or even in plant pots.

Sphaerobolus stellatus Persoon

is more distantly related and grows on decaying leaves, bracken fronds, partially buried twigs and dung. It is an intriguing fungus because it possesses a remarkable spore-dispersal mechanism. The inner layer of the fruit-body when ripe suddenly turns inside out catapulting the inner spore-mass to distances of anything up to 4,200 mm, that is a distance of 1,000 times the size of the fruit-body. The fruit-body is externally whitish or pale yellow, but this layer splits into lobes like a star exposing the bright orange inner surface and pale spore-mass.

Illustrations: Crucibulum laeve—LH 223; WD 111⁷. Cyathus striatus—LH 223; WD 111⁹. Sphaerobolus stellatus—LH 223; WD 111⁵.

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