Home › M › Mushrooms (Popular name given to a group)

Mushrooms (Popular name given to a group)

The popular name given to a group of Fungi, very numerous in species, but with a strong family likeness, which renders them easily recognisable, as will be seen from the subjoined figures (Figs. 610 and 611). In a limited sense, the name is often used to denote certain edible Fungi; but, in a wider sense, it includes many useless and poisonous kinds, such as Toadstools, the Fly Agaric, and numerous others belonging to the genus Agaricus, as well as to certain allied genera, viz., Boletus, Cortinarius, Hydnum, Lactarius, &c.; and it is even used occasionally, but incorrectly, to denote all Fungi. Excluding this last sense, the Mushrooms, in their commonly-known condition, are only the spore-bearing parts of the plants, and arise from a dense network of filaments (mycelium) buried in soil containing decaying matter, or in the wood of dying or dead trees. These spore-bearers generally resemble a cap (pileus), supported on a stalk, which is fixed to the lower surface of the cap in the middle, or, less frequently, to one side of it. The cap may vary from 1/2in. to about 1ft. across, and the stalk also varies much in length and in thickness. On the lower surface of the cap is spread the hymenium, or surface on which the spores are formed. These are fixed to short, slender stalks, of which four stand on the free end of each of certain large cells (basidia), which are scattered over the hymenium. The latter varies much in the mode of attachment to the cap, and in the degree and modes of folding that it undergoes. The genera and species nearly related to the true Mushrooms have it easily separable from the tissue of the cap; but Polyporus, and certain allied forms have it closely grown to the latter. The surface over which the hymenium is spread, is very much increased, in most of the genera, by being folded in various ways.

In Agaricus, the genus to which the great majority of Mushrooms belong, the lower surface of the cap bears numerous thin plates (gills), hanging downwards, and radiating from the stalk to the circumference; and on the sides of these the spores are formed. The gills may be continued unbroken into the stem, or may be separated from it by a narrow space. This difference in the gills, the varied colours of the spores, and the presence or absence of the veil--a membrane passing, in the young Mushroom, from the edge of the cap to a ring round the stalk--are all important characters in determining the genus and species of Mushroom under examination. In Hydnum, the hymenium is scattered over fleshy, tapering outgrowths, or teeth, on the lower surface of the cap; in Boletus and Polyporus, the surface is formed by reticulately-joined ridges, that leave tubes, or pores, between them; in Craterellus, it is smooth, or merely wrinkled. Mushrooms vary exceedingly in colour, the upper surface of the cap usually showing more decided tints than the stalk. Many are white; others yellow; others red in various tints; others show shades of grey or brown, at times almost passing into black. A smaller proportion are some shade of blue. or of metallic green; but they do not show a pure leafgreen, dependent on the presence of chlorophyll, since they never contain this substance. The surface of the cap is usually smooth; it may be sticky, hairy, warty, &c. Some species change colour, at once or gradually, if any part is broken. This is peculiarly noticeable in some kinds of Boletus, in which the bruised surfaces become an intense blue. The change to blue is to be regarded as a sign that the Mushrooms which show it are poisonous or suspicious in their properties. The smell of Mushrooms is slightly peculiar, and is usually not difficult to recognise, there being in it something that reminds one of a closed, mouldy vault or cellar. In decay, most of them emit a strong nitrous smell, some have a most disagreeably foetid stench, but others are rather pleasantly scented, like newly dried hay. A curious property of some Fungi is the luminosity they display. In some kinds, the light is so strong that, in dark places, the plants can be seen from a considerable distance. This phenomenon is manifested by species in various groups of Fungi; but the most striking examples are met with in the genus Agaricus, several members of which have been observed to be luminous, apparently in the healthy state. In some, the cap and stalk emit light; but more frequently the mycelium in decaying wood is the luminous part. Another characteristic of some Mushrooms--e.g., the genus Lactarius and several species of Agaricus--is the appearance, on broken or cut surfaces, of a milky fluid--the latex--which pours out from long tubular cells in the tissues of the plant. This fluid may be white, yellow, or orange; and, at times, changes colour after being exposed to the air for a short time. In some cases, the latex has a pleasant taste, while, in others, it is very acrid. Mushrooms, like Fungi in general, are propagated by means of spores, which, as already mentioned, are borne on large cells (basidia), produced on the hymenium. These spores can be obtained by laying the Mushrooms, gills downwards, on paper, which should be of a tint to contrast with them in colour. They will be found to map out on the paper the arrangements of gills or pores, and, in this way, their colour in mass also can be easily detected. The colour of the spores is largely employed in breaking up the very large genus Agaricus into sub-genera of more convenient size.

Uses. Mushrooms and their allies include almost all the Fungi that can be regarded as of direct use to man as food-plants. A considerable number have been, or are, used in diet, either because of the amount of nitrogenous matter in them, or as imparting a pleasant flavour to the articles, with which they are served at table. But, while it is comparatively easy to recognise certain of the well-known edible Mushrooms, great care is required to prevent serious results when poisonous species are gathered by mistake, and eaten with the useful ones. Such a mistake is not infrequent, since a very great resemblance exists between certain poisonous and edible kinds. The Mushroom most generally esteemed in Britain is the Common Mushroom (Agaricus campestris), It is so well known as scarcely to call for a detailed description of its appearance. It is largely cultivated, but it is also frequently abundant in pastures, especially in natural grass land or meadows. At first, the gills are pale pink, or salmon-tinted, but they deepen into a peculiar purplish-brown. The upper surface of the cap varies somewhat in colour and smoothness, and there is a permanent ring of tissue around the stem, a little way below the cap. This Mushroom does not enjoy the same high reputation on the Continent of Europe that it possesses among ourselves; and, in Italy, it is said to be regarded by the labouring classes as even poisonous, or, at least, suspicious. A nearly allied kind, the Meadow or Horse Mushroom (A. arvensis), is considerably larger than the last, and grows in similar localities; but its cap is pure white on the top while young, and it has paler gills than A. campestris. It is often gathered in large quantities for sale, but is somewhat less delicate than the Common Mushroom in its flavour. These are most abundant in autumn, but the St. George's Mushroom (A. gambosus,), a large species, appears in spring. For this reason, and because of its flavour, it is much esteemed, and fetches a high price. The cap is nearly white, the gills are pale yellowish, and there is no ring on the stalk. It can be dried so as to retain its characteristic flavour. It smells strongly of new meal. Numerous other species of the genus Agaricus are recognised in Britain as edible. Several of these are more abundant in woods than in open places, despite the general rule that Fungi from such localities are more open to suspicion. From among these useful Agarics we may enumerate the following, which, for the most part, are less generally known than are the preceding; and which are somewhat dangerous to use, from their resemblance to certain kinds which are often to be found in similar localities: A. fragrans and A. odorus, both with a scent like aniseed; A. maximus, white, may reach 14in. in breadth of cap; A. ostreatus and A. ulmarius, found on Elm trunks, both with stalk attached to one side of the cap; and A. prunulus, a white Mushroom, with a smell like meal, found growing in woods. Berkeley, in his "Cryptogamic Botany," p. 367, says that at least a tenth of the species of Agaricus are esculent. Other Mushrooms belonging to genera nearly allied to Agaricus are scarcely, if at al, inferior to its species in their value as food-plants for man; nor would the generic differences between them and Agaricus strike anyone not a botanist as of much importance. The more valuable of these edible forms are Marasmius oreades (see Marasmius) and Coprinus comatus. The latter is esteemed while the gills are still whitish or reddish in colour, but it soon becomes soft, and deliquesces into an inky fluid; it is common in pastures and other open places. Several species of Cortinarius (a genus with rust-coloured spores and a web-like veil) are also edible. All of them inhabit woods. Among them may be noted C. violaceus and C. cinnamomeus, characterised by their colours, to which they owe their specific names. In the genus Lactarius, notable because of the milky juice that its species contain, several are dangerous and acrid; but others are esculent, their juice being mild and pleasant in flavour. The quality of L. deliciosus is sufficiently indicated by its name. This Mushroom is an exception to the rule that change of colour in broken parts is to be regarded as a sign of poisonous properties, since the milk in it, when fresh, is saffron-coloured, but, when exposed to the air, becomes dull green. The genus Russula also includes both poisonous and edible species, but need not be dwelt on here, as the latter are not largely used. Cantharellus cibarius, or the Chantarelle, is one of the best of edible