mushroom can be seen by digging up from a bed a group of very young
plants, such a group as is shown in Fig. 3. Here the white strands are
more numerous than can readily be found in the lawns and pastures where
the plant grows in the feral state.

[Illustration: FIGURE 4.--Agaricus campestris. Sections of "buttons" at
different stages, showing formation of gills and veil covering them.
(Natural size.)]

=Nature of Mushroom Spawn.=--This spawn, it should be clearly
understood, is not spawn in the sense in which that word is used in fish
culture; though it may be employed so readily in propagation of
mushrooms. The spawn is nothing more than the vegetative portion of the
plant. It is made up of countless numbers of delicate, tiny, white,
jointed threads, the _mycelium_.

=Mycelium of a Mold.=--A good example of mycelium which is familiar to
nearly every one occurs in the form of a white mold on bread or on
vegetables. One of the molds, so common on bread, forms at first a white
cottony mass of loosely interwoven threads. Later the mold becomes black
in color because of numerous small fruit cases containing dark spores.
This last stage is the fruiting stage of the mold. The earlier stage is
the growing, or vegetative, stage. The white mycelium threads grow in
the bread and absorb food substances for the mold.

[Illustration: FIGURE 5.--Agaricus campestris. Nearly mature plants,
showing veil stretched across gill cavity. (Natural size.)]

=Mushroom Spawn is in the Form of Strands of Mycelium.=--Now in the
mushrooms the threads of mycelium are usually interlaced into definite
strands or cords, especially when the mycelium is well developed. In
some species these strands become very long, and are dark brown in
color. Each thread of mycelium grows, or increases in length, at the
end. Each one of the threads grows independently, though all are
intertwined in the strand. In this way the strand of mycelium increases
in length. It even branches as it extends itself through the soil.

=The Button Stage of the Mushroom.=--The "spawn" stage, or strands of
mycelium, is the vegetative or growing stage of the mushroom. These
strands grow through the substance on which the fungus feeds. When the
fruiting stage, or the mushroom, begins there appear small knobs or
enlargements on these strands, and these are the beginnings of the
button stage, as it is properly called. These knobs or young buttons are
well shown in Fig. 3. They begin