This mycelium is but a thread-like mass of simple cells joined together at their ends and interlacing in a way a thousand-fold more intricate than a Chinese puzzle. Nothing in its structure indicates what its special product will be. The fungus which is plucked from it is in all its parts simply a mass of these threads—cells strung together, interlacing and ramifying.
When the season favors, the mycelium—which has, winter and summer and from year to year, lived its hidden life, or has sprung from a germinating spore—develops a number of its cells in a minute knob, small as a pin head. At this point the cells make special growth efforts to bring themselves within the favoring influences of heat and moisture; this tiny knob labors within itself, producing cell after cell, which takes shape and function for the future toadstool.
As it rapidly enlarges it pushes its way toward the surface of the ground, becomes more or less egg-shaped in this stage of its growth, and if cut in half longitudinally and examined, it will display what it is going to be when it grows up.
Suppose that it belongs to the first of the two great sections into which fungi are divided under the classification of Fries, who modified that of Persoon. The first has the spores—which represent the seeds in plants—naked, and it is called sporifera or spore-bearing. The second, which has the spores enclosed in cells or cysts, is called sporidifera or sporidia-bearing. If the cap of a gill-bearing toadstool be laid, gills downward, on a watch crystal or piece of white paper for a few hours, or, in some instances, a few minutes, a complete representation of the spaces between the gills will be found deposited as an impalpable powder. These are the spores.
The first section is divided into four cohorts. Two of these have hymeniums or spore-bearing surfaces more or less expanded. These are Hymenomycetes and Gastromycetes. In Hymenomycetes the hymenium is always exposed in matured plants, as with the common mushroom. When young, some plants are covered with a membrane. In Gastromycetes the hymenium is always concealed within a covering which bursts at maturity, as with the Lycoperdons or puff-balls. Cohort Coniomycetes includes rusts, smuts, etc., formed for the most part on living plants. There is no hymenium present. The spores are produced on the ends of inconspicuous threads, free or enclosed in a bottle-like receptacle called a perithecium. Cohort Hypomycetes is composed of those species of fungi commonly called molds. The spores are produced, naked, from the ends of inconspicuous threads.
In the Agaricaceæ—the first family in Hymenomycetes—the young plant is completely enveloped. (Plate [III], fig. B, p. 2.) Its head is as yet undefined and its body may be classed as dumpy, but shut in and protected are a great quantity of knife-like plaits (Plate [III], fig. C., p. 2), on the outer surface of which, when the plant matures, will be borne its spores. It therefore belongs to the Hymenomycetes, and to the Family Agaricaceæ—gill-bearing.
If the ground becomes moist or there comes a heavy dew or a rain, the young plant, closely compacted and very solid, which has been under the surface for many days waiting its chance to get forth to light and air, rapidly swells, breaks through the moistened earth, goes rapidly to cell-making, ruptures its outside covering, the head expands and in so doing spreads out its gills or hymenium. (Plate [III], figs. C, D, E, p. 2.) The membrane which covered the gills either vanishes, or gathers round the stem in the form of a ring or circular apron, or it may partially adhere to the edges of the top, cap or pileus and hang as a fringe from it; the stem elongates; the whole plant assumes the colors of its species and in a few hours or days at most it stands forth, a marvel of beauty, structure and workmanship.
But little is known of how these spores reproduce themselves. The microscope fails to completely penetrate the mystery. A whole fungus is but a mass of cells, the spore is but one of them. That these simple cells do produce after their kind there is no doubt, but so minute is the germ and hidden its methods that science has failed to solve them.
The first Family of Hymenomycetes is Agaricaceæ. Its members always have gills or modifications of them. In some cases—notably in Cantharellus—the gills have the appearance of smooth, raised veins over which is the spore-bearing surface. The hymenium is but an extension of the fibers of the cap, folded up like the plaits and flutings of ruffles, and laundered with exquisite neatness. If it is carefully detached and spread out like a fan it will cover a large surface, many times the size of the cap from which it has been taken, and will show that what is a consumption of material in dress ornamentation is utilized by economical Dame Nature to increase the spore-bearing surface within a small space and for purely business purposes—spore-bearing. The color of these spores has much to do with the classification. The microscope with high light reveals the delicate shades of their coloring, but the main colors are readily distinguished by the naked eye when the spores are collected in a mass on glass or paper.
The Polyporaceæ have in place of gills closely packed tubes on the inside of which is the spore-bearing surface; each has a mouth from which to eject the spores.