Figure 4.—Small portion of a section through the spore-bearing part of a morel in which the spores are produced in little sacs or asci. (a) An ascus, (b) an ascus discharging its spores, (c) the spores, (d) sterile cells. Highly magnified.—Longyear.
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.
Figure 5.--Small portion of a stem of a morel showing cell filaments. Highly magnified.—Longyear.
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.