The fructiferous surface in the higher fungi is essentially turned away from the light, yet, although in many of the lower Agarics it is uppermost and exposed, such is the tendency to produce the fructification on the lower side, especially in the Polyporei, that if the position of the plant be reversed the hymenium or fructiferous surface is gradually obliterated and a new one is formed on the other side.
The Polyporei abound in the tropical forests, but species are found in all latitudes. The higher fungi are more or less plentiful in forests everywhere, and every genus of trees seems to have one or more species of fungus peculiar to itself. The Boleti, a genus of the Polyporei, which are thick fleshy fungi of various forms, and for the most part brilliantly coloured, grow under trees in the temperate zones, sometimes in conspicuous circles. When a slice of the Boletus luridus, cyanescens, or other species is exposed to the air, the white fleshy part acquires a blue tint in consequence of the action of ozone upon the acetate of aniline, which was ascertained by Dr. Phipson to be a constituent of these fungi. According to M. Dutrochet more heat is evolved by the Boletus æneus than by any other vegetable except the Arum.
The Polyporei destroy decaying trees and timber, and the Merulius lacrymans or common house fungus, attacks and induces the decay of timber previously sound. The cap is large, fleshy, spongy and moist, but delicate and velvety on the under-side, with wide porous dentate folds. The plant is yellow with a white woolly margin. It grows in a circle, and its mycelium attracts moisture from the atmosphere, which falls down in drops from the pileus. The decay of wood induced by the attacks of this mischievous fungus, is what is called dry rot.
The four principal sub-orders of the Hymenomycetes, or highest fungi, have a cap or pileus, and an inferior fructiferous surface characterized by gills, pores, or tubercles, and are connected by intermediate species; but the other two sub-orders are quite different. The Clavariei are club-shaped, upright, branching fungi, with the fructification surrounding the uppermost extremity of some of the stems. The finest species grow in the Swiss forests where they form an article of food; some are edible in Britain, but of smaller size.
The Tremellini consists of plants forming a gelatinous mass of a bright orange, purple, or dark brown colour, which may be seen on rotten sticks in hedges, and in enormous masses resembling the convolutions of an animal’s brain on the stumps of dead trees, or at the base of living ones. They are mostly plants of temperate climates, but the Exidia Auricula Judæ, or Jew’s ear, is universal. All fungi have a mycelium, but in this order it is not apparent. The structure of the fruit, as determined by the microscopic observations of Mr. Berkeley and of M. Tulasne, is unusual. The fructiferous part is very extensive, being uppermost and spread over the surface of the gelatinous mass, so as to follow all its inequalities. Threads rise from this fructiferous surface bearing on their extremities globular cells exhibiting a concentration of coloured matter generally divided into four lobes, and from the upper surface of these globular bodies, a number of flexuous threads spring, carrying on their tips cymbiform spores.[[52]]
In the preceding family (Hymenomycetes) the fruit-bearing surface has free access to the air, but in the group of the Gasteromycetes, which consists of five or six sub-orders, it has neither access to air or light till the fruit is ripe, for the fructification is enclosed in a rind of one or two coats, and springs without a stem from a gelatinous thready, or cellular mycelium. The most important group, Trichogastres, includes the puff-balls, which grow on the ground. Of these the Lycoperdon, found everywhere on pasture grounds and meadows, is a familiar instance. When young it has a milk-white coat filled with closely packed cells, some of which bear naked spores set upon spicules. When mature, the whole of the interior vanishes, leaving nothing but a mass of threads and fruit; the coat becomes brown, bursts open at the top, and gives vent to a cloud of microscopic spores like the finest dust. In general the ball is sessile, or it has merely the rudiment of a stem. The Lycoperdon giganteum, an exceedingly large species, is a native of a warm climate. The tops of some of the branched threads of its hymenium swell into pear-shaped cells surmounted by short spicules ending in spores; when young it is edible, when dry it is used for tinder and as a styptic, and when ignited its fumes possess a property similar to that of chloroform. The Batarrea forms a contrast to the common puff-balls, being mounted on a stem sometimes a foot and a half high. It has several coats enclosing a thick gelatinous substance in which the threads carrying the spores are distinctly spiral and closely twisted.
The sub-order Hypogæi is subterranean, as the name implies. The exterior coat of these fungi is inseparable from the internal matter, which is for the most part fleshy. In some species it is dry, in others it abounds in milky juice; but in all the fruit is formed in hollows excavated in the interior mass. In some species these cavities are traversed by threads, and in many species the spores accumulate in such multitudes within the cavities, as to make it certain that the spicules, on which the spores are borne, produce successive crops. They are set free by the rupture of the rind. A species of the genus Melanogaster, abundant in the south of England, is edible and sold as the red truffle of Bath; but it is far inferior to the real truffle.
The order Phalloidei has a club-shaped or globose head, composed in the interior of large cells mixed with fruit-bearing cavities. This head has a coat consisting of a jelly inclosed between two heterogeneous strata. The whole interior of the fungus deliquesces, changes to a mucilage, and drips out of the exterior coat in drops dark with microscopic spores. The colour of these fungi is often beautiful, but their smell is most loathsome, tainting the air to a considerable distance; yet the gelatinous volva of more than one species—an Ileodictyon—is eaten by the New Zealanders under the name of thunder dirt, and Phallus Mokusin is an article of food in China.
Certain species of these fungi have a rudimentary stem in their early stages, but it becomes full of deep pits or cavities and suddenly acquires an enormous development when the plant approaches maturity. The cavities are at first strongly compressed, but as the stem increases, they acquire a rounder form, till at length their vertical tendency is so strong that the coat or volva of the fungus is ruptured, which could only be effected by a very strong force. Moreover, the stem is fixed to the base by so small a point that the plant could not remain erect were it not for the tubes of the volva which contract on the stem and act as a sustaining force. Thus these very revolting fragile plants afford a very striking instance of mechanical power exerted by vegetable matter.
The Myxogastres are an anomalous group of fungi which often appear as black or coloured spots on dead leaves and twigs. Sometimes their mycelium or spawn is large and conspicuous, as that of the Reticularia maxima, which overruns cucumber beds, choking up the breathing pores, and killing the plants. Species of these fungi are found upon mineral and vegetable substances dead and alive, and the same species grows upon plants of very different affinities, so that they depend upon the atmosphere for their nourishment, and not on their matrix. Like the puff-balls they end their lives in myriads of microscopic dust spores, but they begin it as a gelatinous mass, sometimes sparkling as a gem, brilliant with the metallic tints of gold, silver, steel, or copper.