Mycena galericulata, pileus conic to campanulate, gills decurrent by a tooth, stem fistulose.]

The terms given above are often used in descriptive works, but the most important feature to be noted in the section of the plant is the relation of the gills to the stem. This relation is represented by several distinct types which are sometimes used to limit genera or sub-genera, since the mode of attachment is usually constant in all species of a group. The princ.i.p.al relations of the gills to the stem are described as follows: _Adnate_ when they reach the stem and are set squarely against it (Fig. 247); _decurrent_ when they run down the stem (Fig. 244); _sinuate_ or _emarginate_ when they have a notch or vertical curve at the posterior end (Fig. 246); and _free_ when they are rounded off without reaching the stem (Fig. 243). In all cases when the lamellae reach the stem and are only attached by the upper angle they are said to be _adnexed_. This term is often used in combination with others, as _sinuate-adnexed_ (Fig. 248, small figure), or _ascending adnexed_ (Fig.

248, larger plant). Sometimes the lamellae are adnate, adnexed, etc., and have a slight decurrent process or tooth as in _Mycena galericulata_ (Fig. 245). In many plants the gills separate very readily from the stem when the plants are handled. Sometimes merely the expansion of the pileus tears them away, so that it is necessary to use great caution, and often to examine plants in different stages of development to determine the real condition of the lamellae.

[Ill.u.s.tration: FIGURE 246. FIGURE 247. FIGURE 248.

FIGURE 246.--Tricholoma, gills sinuate, stipe solid.

FIGURE 247.--Panaeolus papilionaceus, gills adnate.

FIGURE 248.--Left-hand small plant, Hygrophorus, gills sinuate, adnexed.

Right-hand plant Panaeolus retirugis, gills ascending adnexed, veil appendiculate.]

In certain genera the gills have special characteristics which may be noted here. Usually the edge of the lamellae is _acute_ or sharp like the blade of a knife, but in _Cantharellus_ and _Trogia_ the edges are very blunt or obtuse. In extreme forms the lamellae are reduced to mere veins or ridges. Again, the edge is generally _entire_, i. e., not noticeably toothed, but in _Lentinus_ it is often toothed or cut in various ways.

In some other plants the edges are _serrulate_, _crenulate_, etc. In _Schizophyllum alneum_, a small whitish plant very common on dead sticks, the gills are split lengthwise along the edge with the halves revolute, i. e., rolled back. In _Coprinus_ the gills and often a large part of the pileus melt at maturity into a dark, inky fluid.

[Ill.u.s.tration: FIGURE 249.--Section of portion of gill of Marasmius cohaerens. _t_, trama of gill; _sh_, sub-hymenium; _h_, hymenium layer.

The long, dark cells are brown cystidia, termed spicules by some to distinguish them from the colorless cystidia. The long cells bearing the oval spores are the basidia.]

[Ill.u.s.tration: FIGURE 250.--Inocybe repanda (Bull.) Bres. (= Entoloma repandum Bull.). _t_, trama of pileus; _sh_, sub-hymenium; _h_, the hymenial layer; the long cells with a drop of moisture at the ends are cystidia (sing. cystidium).]

=The hymenium.=--The term _hymenium_ is applied to the spore-bearing tissue of many fungi. In the _Agaricaceae_ the hymenium covers the entire surface of the gills and usually the portion of the pileus between the gills. It originates in the following manner: the threads forming the trama of the gills grow out from the lower side of the pileus and perpendicular to its under surface. As growth advances many branches of the threads turn outward toward either surface of the gill and finally terminate in club-shaped cells. These cells, therefore, lie side by side, perpendicular to the surface, forming a pavement, as it were, over the entire surface of the gills. Some of them put out four little p.r.o.ngs, on each of which a spore is borne, while others simply remain as sterile cells (Figs. 249, 250). The spore-bearing cells are _basidia_; the others are called _paraphyses_. They resemble each other very much, except that the basidia bear four _sterigmata_ and a spore on each. In a few species the number of sterigmata is reduced to two and in some low forms the number is variable. The layer just beneath the basidia is usually more or less modified, being often composed of small cells different from the rest of the trama. This is called the _sub-hymenial_ layer or _sub-hymenium_ (Fig. 250).

Other cells called _cystidia_ occur in the hymenia of various species distributed through nearly all the genera of the agarics. Cystidia are large, usually inflated, cells which project above the rest of the hymenium (Fig. 250). They originate either like the basidia, from the sub-hymenial cells (Fig. 250), or from special hyphae deeper down in the trama of the gill (Fig. 249). They are scattered over the entire surface of the hymenium, but become more numerous on the edge of the lamellae.

Their number is much smaller than that of the basidia, but in some species where they are colored they may greatly change the appearance of the gills. Cystidia often secrete moisture which collects in drops at their tips, a phenomenon common to all free fungous cells.

=The stem.=--The stem is usually fixed to the center of the pileus, but it may be _eccentric_, i. e., fixed to one side of the center, or entirely lateral. When the stem is wanting the pileus is _sessile_. With regard to its interior the stem is _solid_, when it is evenly fleshy throughout (Fig. 246), or _hollow_ when the interior is occupied by a cavity (Fig. 248). If the cavity is narrow and tubular the stem is _fistulose_ (Fig. 245); and if the center is filled with a pithy substance it is _stuffed_ (Fig. 243). These terms apply only to the natural condition of the stem, and not the condition brought about by larvae, which eat out the interior of the stem, causing it to be hollow or fistulose.

The terms applicable to the consistency of the stem are difficult to define. In general, stems may be either _fleshy_ or _cartilaginous_. The meaning of these terms can best be learned by careful study of specimens of each, but a few general characters can be given here. Fleshy, fibrous stems occur in the genera _c.l.i.tocybe_ and _Tricholoma_, among the white-spored forms. Their consistency is like that of the pileus, namely, made up of fleshy, fibrous tissue. They are usually stout, compared with the size of the plant, and when bent or broken they seem to be more or less spongy or tough, fibrous, so that they do not snap readily. Cartilaginous stems have a consistency resembling that of cartilage. Their texture is always different from that of the pileus, which is fleshy or membranous. In general such stems are rather slender, in many genera rather thin, but firm. When bent sufficiently they either snap suddenly, or break like a green straw, without separating. In regard to their external appearance some resemble fibrous stems, while others are smooth and polished as in _Mycena_ and _Omphalia_.

=The veil.=--In the young stages of development the margin of the pileus lies in close contact with the stipe, the line of separation being indicated by a kind of furrow which runs around the young b.u.t.ton mushroom. In many genera, as _Collybia_, _Mycena_, _Omphalia_, etc., the pileus simply expands without having its margin ever united to the stipe by any special structure, but in other forms, which include by far the greater number of genera of the _Agaricaceae_ and some _Boleti_, the interval between the stem and pileus is bridged over by threads growing from the margin of the pileus and from the outer layers of the stem.

These threads interlace to form a delicate membrane, known as the _veil_, which closes the gap between the stem and pileus and covers over the young hymenium.

The veil remains firm for a time, but it is finally torn by the expanding pileus, and its remnants persist on the cap and stem in the form of various appendages, whose character depends on the character of the veil. In _Cortinarius_ the veil is made up of delicate threads extending radially from the stem to the margin of the cap without forming a true membrane. From its resemblance to a spider's web such a veil is said to be _arachnoid_. At maturity mere traces of it can be found on the stem. In many genera the veil consists of a delicate membrane which tears away from the stem and hangs in flakes to the margin of the pileus. In these cases the veil is _appendiculate_ (Fig.

248). Frequently it is so delicate that no trace of it remains on the mature plant. Where the veil is well developed it usually remains on the stem as a _ring_ or _annulus_ which becomes free and movable in species of _Lepiota_ (Fig. 242) and _Coprinus_, or forms a hanging annular curtain in _Amanita_, or a thick, felty ring in _Agaricus_, etc. In some plants (species of _Lepiota_) the annulus is continuous with the outer cortex of the stem, which then appears as if it were partially enclosed in a sheath, with the annulus forming a fringe on the upper end of the sheath, from which the apex of the stem projects.

No reference is here made to the _volva_, which encloses the entire plant, and which is described in connection with the genera in which it occurs.

The few typical characters described here will help the student to become familiar with terms applied to them. In nature, however, typical cases rarely exist, and it is often necessary to draw distinction between differences so slight that it is almost impossible to describe them. Only by patient study and a thorough acquaintance with the characters of each genus can one hope to become familiar with the many mushrooms growing in our woods and fields.

CHAPTER XXIV.

a.n.a.lYTICAL KEYS.

By the Author.

CLa.s.s FUNGI.

SUB-CLa.s.s BASIDIOMYCETES.[F]

Plants of large or medium size; fleshy, membranaceous, leathery, woody or gelatinous; growing on the ground, on wood or decaying organic matter; usually saprophytic, more rarely parasitic. Fruiting surface, or hymenium, formed of numerous crowded perpendicular basidia, the apex of the latter bearing two to six (usually four) basidiospores, or the basidiospores borne laterally; in many cases cystidia intermingled with the basidia. Hymenium either free at the beginning, or enclosed either permanently or temporarily in a more or less perfect peridium or veil.

Basidiospores continuous or rarely septate, globose, obovoid, ellipsoidal to oblong, smooth or roughened, hyaline or colored, borne singly at the apex of sterigmata.

Order _Gasteromycetes_. Plants membranaceous, leathery or fleshy, furnished with a peridium and gleba, the latter being sometimes supported on a receptacle. Hymenium on the surface of the gleba which is enclosed within the peridium up to the maturity of the spores or longer; spores continuous, sphaeroid or ellipsoid, hyaline or colored.

Puff-b.a.l.l.s, etc.

Order _Hymenomycetes_. Hymenium, at the beginning, borne on the free outer surface of the compound sporoph.o.r.e, or if at first enclosed by a pseudo-peridium or veil it soon becomes exposed before the maturity of the spores; mushrooms, etc.

HYMENOMYCETES.

a.n.a.lytical Key of the Families.

Plants not gelatinous; basidia continuous. 1

Plants gelatinous or sub-gelatinous, basidia forked, or divided longitudinally or transversely. 4

=1=--Hymenium uneven, i. e., in the form of radiating plates, or folds; or a honey-combed surface, or reticulate, warty, spiny, etc. 2

Hymenium smooth (not as in B, though it may be convolute and irregular, or ribbed, or veined). 3

=2=--Hymenium usually on the under side, in the form of radiating plates, or strong folds. The genus Phlebia in the Hydnaceae has the hymenium on smooth, somewhat radiating veins which are interrupted and irregular. One exotic genus has the hymenium on numerous irregular obtuse lobes (Rhacophyllus). =Agaricaceae.= 17

Hymenium usually below (or on the outer surface when the plant is spread over the substratum), honey-combed, porous, tubulose, or reticulate; in one genus with short, concentric plates. =Polyporaceae.= 171

Hymenium usually below (or on the outer surface when the plant is spread over the substratum), warted, tuberculate, or with stout, spinous processes; or with interrupted vein-like folds in resupinate forms. =Hydnaceae.= 195

=3=--Plants somewhat corky or membranaceous, more or less expanded; hymenium on the under surface (upper surface sterile), or on the outer or exposed surface when the plant is spread over the substratum (margin may then sometimes be free, but upper surface, i. e., that toward the substratum, sterile). (Minute slender spines are sometimes intermingled with the elements of the hymenium, and should not be mistaken for the stouter spinous processes of the Hydnaceae). =Thelephoraceae.= 208

Plants more or less fleshy, upright (never spread over the surface of the substratum), simple or branched. Hymenium covering both sides and the upper surface. =Clavariaceae.= 200

=4=--Basidia forked or longitudinally divided; or if continuous then globose, or bearing numerous spores; or if the plant is leathery, membranous, or floccose, then basidia as described.

Hymenium covering the entire free surface or confined to one portion; smooth, gyrose, folded or lobed; or hymenium lamellate, porous, reticulate or toothed forms which are gelatinous and provided with continuous basidia may be sought here. =Tremellineae.= 204

FAMILY AGARICACEAE.

Pileus more or less expanded, convex, bell-shaped; stipe central or nearly so; or the point of attachment lateral, when the stipe may be short or the pileus sessile and shelving. Fruiting surface usually on the under side and exposed toward the earth, lamellate, or prominently folded or veined. Lamellae or gills radiating from the point of attachment of the pileus with the stipe or with the substratum in the sessile forms; lamellae simple or branched, rarely anastomosing behind, clothed externally on both surfaces with the basidia, each of which bears four spores (rarely two), cystidia often present.

Key to the North American genera.

THE WHITE-SPORED AGARICS.