Botanists unite in describing the plants of this class as being destitute of chlorophyll and of starch. These plants assume an infinite variety of forms, and are propagated by spores which are individually so minute as to be scarcely perceptible to the naked eye. They are entirely cellular, and belong to the class Amphigens, which for the most part have no determinate axe, and develop in every direction, in contradistinction to the Acrogens, which develop from the summit, possessing an axe, leaves, vessels, etc.

Fungi are divided by systematists into two great classes:

1. Sporifera, in which the spores are free, naked, or soon exposed.
2. Sporidifera, in which the spores are not exposed, but instead are enclosed in minute cells or sacs, called asci.

These classes are again subdivided, according to the disposition of the spores and of the spore bearing surface, called the hymenium, into various families.

The sporiferous fungi are arranged into four families, viz:

1. Hymenomycetes, in which the hymenium is free, mostly naked, or soon exposed. Example, "Common Meadow Mushroom."
2. Gasteromycetes, in which the hymenium is enclosed in a second case or wrapper, called a peridium, which ruptures when mature, thus releasing the spores. Example, Common Puff Ball.
3. Coniomycetes, in which the spores are naked, mostly terminal on inconspicuous threads, free or enclosed in a perithecium. Dust-like fungi. Example, Rust of Wheat.
4. Hyphomycetes, in which the spores are naked on conspicuous threads, rarely compacted, Thread-like fungi. Example, Blue Mold.

Of these four subdivisions of the Sporifera, only the Hymenomycetes and the Gasteromycetes contain plants of the mushroom family, and these two together constitute the class known as the Basidiomycetes. The chief distinction of the Basidiomycetes is that the naked spores are borne on the summits of certain supporting bodies, termed basidia. These basides are swollen, club-shaped cells, surmounted by four minute tubes or spore-bearers, called sterigmata, each of which carries a spore. See Figs. 3 and 4, Plate A.

These basides together with a series of elongated cells, termed paraphyses, packed closely together side by side, and intermixed with other sterile cells, called cystidia, constitute the spore-bearing surface or hymenium of the plant.

To the naked eye this hymenium appears simply as a very thin smooth membrane, but when a small portion of it is viewed through a microscope with high powers its complex structure is readily observed and can be carefully studied.

The Sporidiferous fungi are represented by the families Physomycetes and Ascomycetes. The first of these consists wholly of microscopic fungi.

Ascomycetes.—In the plants of this family the spores are not supported upon basidia, but instead are enclosed in minute sacs or asci formed from the fertile cells of a hymenium. In this connection it would be well to state that Saccardo does not recognize the divisions Sporifera and Sporidifera by those names.

They are nearly the equivalent of Basidiomycetes and Ascomycetes.

What Cooke names Physomycetes, Saccardo calls PhycomyceteÆ, introducing it in his work between GasteromyceteÆ and MyxomyceteÆ, which some mycologists consider somewhat out of place.

Saccardo calls its asci (sacs which contain the spores) sporangia. He does not regard them as genuine asci, but as corresponding more to the peridium of the GasteromyceteÆ and MyxomyceteÆ.

Peck says that this group seems to present characters of both Hyphomycetes and Ascomycetes, with a preponderance towards Hyphomycetes.

It is a small group, however, and since it consists wholly of microscopic fungi, need not be farther considered in this work.

In the Ascomycetes are included the sub-families Discomycetes, Pyrenomycetes, and Tuberacei. Of these the Discomycetes and the Tuberacei are the only groups which contain any of the mushrooms, and but few of these are large enough or sufficiently tender to possess value as esculents. A good example of the first (Discomycetes) is found in the Morel, and of the second (Tuberacei) in the Truffle.

In the Discomycetes or "disk fungi," the spores are produced in minute membraneous sacs, each sac usually containing eight spores. These spore sacs are imbedded in the flesh of the exterior and upper surface of the mushroom cap.

In the four classes, Hymenomycetes, Gasteromycetes, Discomycetes, and Tuberacei, therefore, are included all of the plants which are here designated under the generic term of "mushrooms."

Some idea of the relative numerical value of these classes may be obtained from the following figures given by the distinguished British mycologist, M. C. Cooke:

(The Tuberacei comprise a very small group of subterranean fungi, and comparatively few of the species are described.)

Saccardo in his Sylloge gives a total of 42,000 described species of fungi of all classes, including the most minute. Of these the Hymenomycetes include by far the largest number of edible mushrooms.

The family Hymenomycetes is divided into the following six orders: Agaricini, Polyporei, Hydnei, Thelephorei, Clavarei, Tremellini.

In the order Agaricini the hymenium is found on the under surface of the mushroom cap, covering pleats or gills, technically called lamellÆ. These gills vary in character in the different genera, being "persistent in such as the Agaricus, Russula, and Lentinus, deliquescent (melting) in Coprinus, Bolbitius, etc. The edge of the gills is acute in Agaricus, Marasmius, etc., but obtuse and vein-like in Cantharellus, longitudinally channelled in Trogia, and splitting in Schyzophyllum."

In the Polyporei, pore-bearing mushrooms, the gills are replaced by tubes or pores. The tubes are little cylinders, long or short, pressed one against another, forming by their union a layer on the under surface of the cap, and the sporiferous membrane or hymenium lines their inner walls. Their upper end is always closed, while the lower extremity is open to permit the outward passage of the spores. The tubes are generally joined together and are not easily disunited. They are free, i. e., separable, in the sole genus Fistulina. As regards their attachment to the cap, the tubes may be firmly adherent as in the genus Polyporus or easily detached in a single mass as in Boletus, the fleshy form of the order Polyporei. They frequently leave a circular space of greater or less dimensions around the stem, or they adhere to or are prolonged upon it in such a manner that the orifices rise in tiers one above another. The color of the tubes, although not offering as characteristic varieties as that of the gills, changes nevertheless according to species and according to the age of the plant. The tubes may sometimes be of a different color from their orifices, as in Boletus luridus. In some of the Boleti the color of the flesh is changed on exposure to the air and the tubes often assume the same tints. The tubes, generally called pores, are sometimes closely adherent to the substance of the cap, which is often hard, corky, or coriaceous, as seen in most of the Polyporei.

In the Hydnei, spine-bearing mushrooms, the hymenium is seen covering the spines or needle-like processes which take the place of gills in this order, and which project from the under surface of the cap. These spines may be divided or entire, simple or ramified, and are formed of the substance of the cap. In the early stages of development they appear like small projecting points or papillÆ, those on the margin of the cap and at the apex of the stem being always less developed, frequently remaining in this rudimentary state. They are rounded in the species Hydnum imbricatum, sometimes compressed in Hydnum repandum, sometimes terminating in hairs or filaments, as in Hydnum barba Jovis, or very much divided, as in Hydnum fimbriatum.

In the Clavarei, the whole plant consists of solid fleshy masses without any stem of a distinct substance, sometimes club-shaped, sometimes branched with the hymenium smoothly covering the entire surface, never incrusting or coriaceous.

In the Thelephorei, the lower surface of the cap presents neither gills, pores, nor spines, but instead the hymenium covers an uneven or slightly wrinkled surface, partially striate, sometimes obscurely papillose. The plants of this order assume a great variety of shape, from that of a perfect cup with a central stem to an irregularly and much branched frond. They are generally dry and tough. Very few are recommended as edible. Prof. Peck says of this order that probably no edible species will be found in any of its genera outside of the genus Craterellus.

In the order Tremellini we have a great departure from the character of the substance, external appearance, and internal structure of the other orders of the Hymenomycetes. The substance is gelatinous; the form is lobed, folded, or convolute, often resembling the brain of some animal. It is uniformly composed throughout of a colorless mucilage, with no appreciable texture, in which are distributed very fine, diversely branched, and anastomosing filaments. Towards the surface the ultimate branches of this filamentous network give birth to globular cells, both at their summits and laterally, which attain a comparatively large size. These cells are filled with a protoplasm, to which the plant owes its color. The fertile threads are not compacted into a true hymenium.

Representative types of the above-described orders of the Hymenomycetes are shown in Plate B. The various genera, and species of these orders, will be described more in detail in connection with the species illustrated.

---

CLASSIFICATION.

Owing to the fact that botanists of various countries, writing in diverse languages, have for more than a century been engaged in describing the fungi of their respective countries, with their work frequently unknown to one another, it is not surprising that there has been constant revision, or that many changes have been made in the way of classification and nomenclature which to the amateur student are often confusing.

The classification by the pioneer mycologist, Elias Fries, as presented in his several works on fungi, ignored all microscopical characters, and Saccardo's classification, as presented in his Sylloge Fungorum, was the first complete system offered in its place.

Saccardo, in 1882, commenced his Sylloge, of which not less than twelve volumes have been published. In Saccardo's system of classification the six orders of the Hymenomycetes are not essentially different in their arrangement from that of Fries, although Saccardo has raised all the subgenera of Agaricus to the rank of genera, and then altered their sequence so as to bring them into four sections, distinguished by the color of their spores. Having raised the old subgenera of Fries to generic rank, Saccardo found it necessary to limit the application of the term Agaricus to the group of fungi to which it was originally applied by LinnÆus, viz., the common field mushroom Agaricus campester, and its allies, represented by Agaricus arvensis, Agaricus Rodmani, etc., or, as Prof. Peck more definitely states it, "to those of the gilled mushrooms which have brown spores, free gills, a stem bearing a ring, gills generally pink-colored in the early stage, and brownish black when fully matured." M. C. Cooke, the distinguished English mycologist, prefers to retain the genus Agaricus with its original subgenera intact, succeeded by the other genera of Agaricini, as in the Hymenomycetes Europei of Fries, giving as his reason the belief "that for purposes of classification features should be taken which are present and evident in the specimens themselves, and are not dependent on any of their life-history which cannot be presented in the herbarium."

In a work such as the present, which is designed to be popular in character rather than purely technical, it is deemed advisable to select as a basis for classification that system which is most accessible to reference by the general reading public. Saccardo's Sylloge, while exhaustive in character and of inestimable value to the mycologist, is written in Latin, and is, moreover, a very expensive work—facts which render it practically unavailable to the general public.

In the compilation of this series of pamphlets I have adopted the classification of M. C. Cooke, which, as regards the Hymenomycetes, the family containing most of the fleshy fungi, is, with exceptions noted, in accord with that of Saccardo. M. C. Cooke's hand-book of fungi is of convenient size and form for ready reference.

For the convenience, however, of those who may wish to familiarize themselves with both systems, a synopsis of Saccardo's Genera of Hymenomycetes will be given later.

---

STRUCTURAL CHARACTERISTICS OF THE AGARICINI.

By far the greater number of the Agaricini have both cap and stem. The form of the cap, as well as that of the stem, varies somewhat in the different genera and species. Those which are terrestrial in habit are generally of an umbrella-like shape, while those which grow upon trees and decayed tree-stumps are apt to be one-sided or semi-spherical.

In many of the parasitical mushrooms the stem is absent. Where the stem is present it is either an interrupted continuation of the hymenophore or fleshy substance of the cap, or else is supported separately as a pillar on which the cap rests, a more or less distinct line of demarcation showing where the fibers terminate. Sometimes it is quite easily detached from the cap socket, as in the Lepiota procerus. It may be hollow or stuffed, solid or fibrillose. It varies in length and thickness. In some species it is smooth and polished, in others rough and hairy, reticulated, etc., sometimes tapering, sometimes distinctly bulbous at the base.

The spores of the species differ in color and are usually globular or oblong in shape. All of these characteristics assist in determining the species.