those which
have grown in the meadow. In like manner they may be present in the oats
which have been fed to the horse. In the case of stable-fed animals, the
inoculation of the manure in this way may not always be certain or very
free. But in the case of pasture-fed horses which are stalled at night
probably the inoculation is very certain and very abundant, so that a
large number of spores would be present in the manure from horses fed in
this way.

The natural spawn also may originate from spores which are carried by
the wind from the pasture or meadow mushrooms upon manure piles, or
especially from spores which may lodge in the dust of the highways or
street. Many of these spores would cling to the hoofs of the horses and
at night, or at times of feeding, would be left with the manure in the
stall. At other times horse droppings may be gathered from roads or
streets where spores may be present in the dust. The piles of the
droppings accumulated in this way, if left a sufficient time, may
provide natural spawn by this accidental inoculation from the spores.

Probably few attempts have been made to grow the natural spawn with
certainty in this country, though it does not appear to be an
impracticable thing to do, since formerly this was one source of the
virgin spawn in Europe. It is usually obtained by search through stables
and barn yards or other places where piles of horse manure have
accumulated and have remained for several months. In some cases the
growers keep men employed through the summer season searching the yards
and stables over a considerable area for the purpose of finding and
gathering this natural spawn. It is probably termed virgin spawn because
of its origin under these natural conditions, and never having been
propagated artificially.

The natural spawn, as indicated above, is employed for a variety of
purposes. It is used for inoculating the bricks in the manufacture of
brick spawn. It is used for propagating once or twice in the mushroom
beds, for the purpose of multiplying it, either in the manufacture of
brick spawn, or for flake spawn, which is planted directly in the beds
to be used for the crop. In some places in America it is collected on a
large scale and relied on as the chief source of spawn for planting
beds. In such cases the natural or virgin spawn is used directly and is
of the first and most vigorous generation. It is believed by growers who
employ it in this way that the results