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.
Mushroom Gills
Mushroom gills, or lamellæ, anatomically considered, are composed, first, of a central portion, a prolongation of the hymenophore or flesh of the cap, more or less dense, sometimes so thin as to be scarcely perceptible; second, the hymenium or spore-bearing membrane covering the surfaces of this prolonged hymenophore. They are vertical, simple, equal, respectively, or more frequently alternating with shorter gills. They are often evanescent and putrescent, sometimes liquefying altogether. Their color is usually different from the upper surface of the cap, not always similar to that of the spores borne upon them, at least in youth; with age, however, they usually assume the color of the mature spore. The change of color of the gills according to the age of the plant is very important in the study of the Agaricini; it accounts for the white gills of certain species in youth, the pink in maturity, and the brown when aged.
The end of the gill nearest the stalk of the plant is termed the posterior extremity; the opposite end, the anterior extremity. In most of the Agaricini the gills are unequal. Some extend from the margin to about half the space between it and the stem; others are still shorter.
The Volva
The volva is a membrane which envelops the entire plant in embryo, giving it the appearance of an egg. It originates at the base of the mushroom and furnishes it, during its fœtal life, with the means of support and nourishment. Its texture is so delicate that it generally disappears, leaving very little trace of its existence on the adult plant. In many of the volvate species this organ exists only so long as they are under ground, and some mycologists restrict the term “volvati” to such only as retain it afterwards. As the young plant expands it breaks through the top of this volva or wrapper, and, emerging, carries with it patches of the membrane on the upper surface of the cap. These are more or less prominent, numerous, and thick, sometimes irregularly disposed, sometimes regularly in the form of plates, warts, etc. At the base of the stem of the mushroom the remains of the volva are seen in the form of a sort of wrapper. This is more or less ample, thick, and ascending. It is called free when it is loose or easily detached from the stem, and congenital when it cannot be separated from it without laceration. In some species it is distinctly membranous, and in others floccose, and friable in character, sometimes appearing in ridges as a mere border, at others broken up into scales, and, as the plant matures, wholly disappearing. The volva is a feature of great importance in the study of the Agaricini, of the subgenera Amanita, Volvaria, etc.
The Mushroom Veil
The veil is not a constant feature in the Agaricini, at least it is not always visible. When present it consists of a membrane which extends from the margin of the cap to the stem, veiling or protecting the gills. This membrane, called the cortina, has given its name to a numerous and important class of mushrooms (the Cortinarias). It is generally white, soft, slightly spongy, cottony, at times fibrillose or even slightly fibrous, again in texture comparable to the spider’s web, and may be even powdery or glutinous. It exists intact only in the youth of the plant. It is not visible in the developing mushroom, at least while the cap is closely pressed against the stem, but as the cap expands the membrane extends and finally breaks, leaving in some species its remnants upon the margin of the cap and upon the stem in the usual form of a ring or a mere zone. When the stem is not ringed the veil rises high upon the stalk, stretches across to meet the edges of the cap, and is afterwards reflected back over its whole surface.
Mushroom Spores and Mycelium
The spore is the reproductive organ of the mushroom. It differs from the seed of the flowering plant in being destitute of an apparent embryo. A seed contains a plantlet which develops as such. A spore is a minute cell containing a nucleus or living germ, the reproductive cell germ called by some authors the germinating granule. This in turn throws out a highly elongated process consisting of a series of thread-like cells branching longitudinally and laterally, at length bifurcating and anastomosing the mass, forming the vegetative process known as mycelium or mushroom spawn.
On this mycelium, at intervals, appear knob-like bodies, called tubercles, from which the mushrooms spring and from which they derive their nourishment. See Fig. 5, Plate A.
Where the conditions have been unfavorable this mycelium has been known to grow for years without bearing fruit.
Mushroom spores are very variable in size, shape, and color, but are generally constant at maturity in the same genus. Their shape, almost always spherical in the young plant, becomes ovate, ellipsoidal, fusiform, reniform, smooth, stellate, sometimes tuberculate, or remains globose. This feature, varying thus with the age of the plant, should be studied in the mature plant.
Mycelium
De Leveille has thus defined mycelium: “Filaments at first simple, then more or less complicated, resulting from the vegetation of the spores and serving as roots to the mushroom.”
The mycelium of mushrooms or the mushroom spawn is usually white, but is also found yellow, and even red. It is distinguished by some writers as nematoid, fibrous, hymenoid, scleroid or tuberculous, and malacoid. The nematoid mycelium is the most common. Creeping along on the surface of the earth, penetrating it to a greater or less depth, developing in manure among the débris of leaves or decayed branches, always protected from the light, it presently consists of very delicate filamentous cells more or less loosely interwoven, divided, anastomosing in every direction and often of considerable extent.
Its presence is sometimes difficult to detect without the use of the microscope, either on account of its delicacy or because of its being intermingled with the organic tissues in which it has developed.
Sometimes mycelium unites in bundles more or less thick and branched. This has been called the fibrous mycelium. Where the filaments intercross closely, are felted, and inclined to form a membrane, it is hymenoid mycelium. Where the filaments are so small and close that they form very compact bodies, constituting those solid irregular products called sclerotium, it is scleroid or tuberculous mycelium. With malacoid mycelium we have nothing to do in this paper. It is a soft, pulpy, fleshy mycelium.
Systematists have divided the Agaricini into groups according to the color of their spores. These groups are defined as follows by various authors:
According to—
Elias Fries, 5 groups: Leucosporus, white; Hyporhodius, pink; Cortinaria, ochraceous; Derminus, rust; Pratella, purplish black.
Rev. J. M. Berkeley, 5 groups: Very frequently pure white, but presenting also pink, various tints of brown, from yellowish and rufous to dark bister, purple-black, and finally black; Leucospori, white; Hyporhodii, salmon; Dermini, ferruginous; Pratellæ, brown; Coprinarius, black.
Dr. Badham, 6 groups: Pure white or a yellow tinge on drying; brown; yellow; pink; purple; purple-black; some pass successively from pink to purple and from purple to purple-black.
Mrs. Hussey, 11 shades: White; rose; pale ocher; olivaceous-ocher; reddish-ocher; ochraceous; yellowish olive-green; dull brown; scarcely ferruginous; snuff-color; very dark brown.
Hogg & Johnson, 5 groups: Leucosporei, white; Hyporhodii, salmon; Dermini, rusty; Pratellæ, purplish-brown; Coprinarii, black.
C. Gillet, 7 shades: White; pink; ochraceous; yellow; ferruginous; black or purplish black; round, ovate, elongated, or fusiform, smooth, tuberculate or irregular, simple or composite, transparent or nebulous, etc.
Jules Bel, 5 groups: White; pink; red; brown; black.
Dr. Gautier, 5 shades: White; pink; brown; purplish-brown; black.
Constantin & Dufour, 5 groups: White; pink; ochraceous; brownish-purple; black.
J. P. Barla, 7 groups: Leucosporii, white; Hyporhodii, pink; Cortinariæ, ochraceous; Dermini, rust; Pratellæ, purplish-black; Coprinarii, blackish; Coprini and Gomphi, dense black.
L. Boyer, 5 groups, 11 shades: White to cream yellow; pale pink to ochraceous yellow; bay or red brown to brown or blackish bister; rust color, cinnamon or light yellow.
W. D. Hay, 5 groups: White; pink; brown; purple; black.
C. H. Peck, 5 groups: Leucosporii, white; Hyporhodii, salmon; Dermini, rust; Pratellæ, brown; Coprinarii, black.
Saccardo divides the Agaricini into four sections, according to the color of their spores, as follows: Spores brown, purplish brown or black, Melanosporæ; spores ochraceous or rusty ochraceous, Ochrosporæ; spores rosy or pinkish, Rhodosporæ; spores white, whitish or pale yellow, Leucosporæ.
Dr. M. C. Cooke, 5 groups: Leucospori, white or yellowish; Hyporhodii, rosy or salmon color; Dermini, brown, sometimes reddish or yellowish brown; Pratellæ, purple, sometimes brownish purple, dark purple, or dark brown; Coprinarii, black or nearly so.
These shades are somewhat different from the colors of the mushrooms’ gills, so that, when it is of importance to determine exactly the color of the spore in the identification of a species, we may without recourse to the microscope cut off the stem of an adult plant on a level with the gills and place the under surface of the cap upon a leaf of white paper if a dark-spored species, and upon a sheet of black paper if the spores are light. At the expiration of a few hours we will find, on lifting the cap, a bed of the shed spores which will represent their exact shade. These may be removed to a glass slide and their size and form determined by means of the microscope.
In the present work Dr. M. C. Cooke’s grouping of the spore series is adopted.