The development of the spores is quite interesting. The young basidia as seen in Figure 2 are filled with a granular protoplasm. Soon small projections, called sterigma (plural, sterigmata), make their appearance on the ends of the basidia and the protoplasm passes into them. Each projection or sterigma soon swells at its extremity into a bladder-like body, the young spore, and, as they enlarge, the protoplasm of the basidium is passed into them. When the four spores are full grown they have consumed all the protoplasm in the basidium. The spores soon separate by a transverse partition and fall off. All spores of the Hymenomycetous fungi are arranged and produced in a similar manner, with their spore-bearing surface exposed early in life by the rupture of the universal veil.

In the puff-balls the spores are arranged in the same way, but the hymenium is inclosed within an outer sack. When the spores are ripe the case is ruptured and the spores escape into the air as a dusty powder. The puff-balls, therefore, belong to the Gastromycetous fungi because its spores are inclosed in a pouch until they are matured.

Another very large group of fungi is the Ascomycetes, or sac fungi. It is very easily determined because all of its members develop their spores inside of small membranous sacs or asci. These asci are generally intermixed with slender, empty asci, or sterile cells, called paraphyses. These asci are variously shaped bodies and are known in different orders by different names, such as ascoma, apothecium, perithecium, and receptacle. The Ascomycetes often include among their numbers fungi ranging in size from microscopic one-celled plants to quite large and very beautiful specimens. To this group belong the great number of small fungi producing the various plant diseases.

In a work of this kind especial attention is naturally given to the order of Discomycetes or cup fungi. This order is very large and is so called because so many of the plants are cup shaped. These cups vary greatly in size and form; some are so small that it requires a lens to examine them; some are saucer-shaped; some are like goblets, and some resemble beakers of various shapes. The saddle fungi and morels belong to this order. Here the sac surface is often convoluted, lobed, and ridged, in order to afford a greater sac-bearing surface.

In the mushrooms, puff-balls, etc., we find the spores were borne on the ends of basidia, usually four spores on each. In this group the spores are formed in minute club-shaped sacs, known as asci (singular, ascus). These asci are long, cylindrical sacs, standing side by side, perpendicular to the fruiting surface. Figure 4 will illustrate their position together with the sterile cells on the fruiting surface of one of the morels. They usually have eight spores in each sac or ascus.

The stem of the mushroom is usually in the center of the cap, yet it may be eccentric or lateral; when it is wanting, the pileus is said to be sessile. The stem is solid when it is fleshy throughout, or hollow when it has a central cavity, or stuffed when the interior is filled with pithy substance. The stems are either fleshy or cartilaginous. When the former, it is of the same consistency as the pileus. If the latter, its consistency is always different from the pileus, resembling cartilage. The stem of the Tricholoma affords a good example of the fleshy stemmed mushroom, and that of the Marasmius illustrates the cartilaginous.

If the cap or stem of a mushroom is examined with a microscope of high magnifying power it will be found to be made up of a continuation of the mycelial filaments, interlaced and interwoven, branching, and the tubular filaments often delicately divided, giving the appearance of cells. Figure 5 represents a small portion of a Morel stem highly magnified showing the cell filaments. In soft fungi the mycelial threads are more loosely woven and have thin walls with fewer partitions.

The veil is a thin sheet of mycelial threads covering the gills, sometimes remaining on the stem, forming a ring or annulus. This sometimes remains for a time on the margin of the cap when it is said to be appendiculate. Sometimes it resembles a spider's web when it is called arachnoid.

The volva is a universal wrapper, surrounding the entire plant when young, but which is soon ruptured, leaving a trace in the form of scales on the cap and a sheath around the base of the stem, or breaking up into scales or a scaly ring at the base of the stem. All plants having this universal volva should be avoided, further than for the purpose of study. Care should be taken that, in their young state, they are not mistaken for puff-balls. Frequently when found in the egg state they resemble a small puff-ball. Figure 6 represents a section of an Amanita in the egg-state and also the Gemmed puff-ball. As soon as a section is made and carefully examined the structure of the inside will reveal the plant at once. There is but little danger of confusing the egg stage of an Amanita with the puff-ball, for they resemble each other only in their oval shape, and not in the least in their marking on the surface.

=WHAT IS A FUNGUS OR A MUSHROOM?= It is a cellular, flowerless plant, nourished by the mycelium which permeates the soil or other substances on which the fungus or mushroom grows. All fungi are either parasites or saprophytes which have lost their chlorophyll, and are incapable of supporting an independent existence.

There is a vast number of genera and species, and many have the parasitic habit which causes them to enter the bodies of other plants and of animals. For this reason all fungi are of economic importance, especially the microscopic forms classed under the head of Bacteria. Some recent writers are inclined to separate the Bacteria and slime-molds from the fungus group, and call them fungus animals. However this may be, they are true plants and have many of the characteristics of the fungi. They may differ from the fungi in their vegetative functions, yet they have so many things in common that I am inclined to place them under this group.

Many, such as the yeast fungus, the various fermentative fungi, and the Bacteria concerned in the process of decomposition, are indeed very useful. The enrichment and preparation of soils for the uses of higher plants, effected by Bacteria, are very important services.

Parasites derive their nourishment from living plants and animals. They are so constituted that when their nourishing threads come within range of the living plant they answer a certain impulse by sending out special threads, enveloping the host and absorbing nutrition. Saprophitic plants do not experience this reaction from the living plants. They are compelled to get their nourishment from decaying products of plants or animals, consequently they live in rich ground or leaf mold, on decayed wood, or on dung. Parasites are usually small, being limited by their host. Saprophytes are not thus limited for food supply and it is possible to build up large plants such as the common mushroom group, puff-balls, etc.

The spores are the seeds or reproductive bodies of the mushroom. They are very fine, and invisible to the naked eye except when collected together in great masses. Underneath mushrooms, frequently, the grass or wood will be white or plainly discolored from the spores. The hymenium is the surface or part of the plant which bears the spores. The hymenophore is the part which supports the hymenium.

In the common mushroom, and in fact many others, the spores develop on a certain club-like cell, called basidium (plural, basidia), on each of which four spores usually develop. In morels these cells are elongated into cylindrical membranous sacs called asci, in each of which eight spores are usually developed. The spores will be found of various colors, shapes, and sizes, a fact which will be of great assistance to the student in locating strange species and genera. In germination the spores send out slender threads which Botanists call mycelium, but which common readers know as spawn.

The method and place of spore development furnish a basis for the classification of fungi. The best way to acquire a thorough knowledge of both our edible and poisonous mushrooms is to study them in the light of the primary characters employed in their classification and their natural relation to each other.

There is a wide difference of opinion as to the classification of mushrooms. Perhaps the most simple and satisfactory is that of Underwood and Cook. They arrange them under six groups:

1. Basidiomycetes--those in which the spores or reproductive bodies are naked or external as shown in illustration 2 on page 15.

2. Ascomycetes--those in which the spores are inclosed in sacs or asci. These sacs are very clearly represented in illustration Figure 4 on page 18. This will include the Morels, Pezizae, Pyrenomycetes, Tuberaceae, Sphairiacei, etc.

3. Physcomycetes--including the Mucorini, Saprolegniaceae, and Peronosporeae. Potato rot and downy mildew on grape vines belong to this family.