e mycelium; the term "spawn" includes both
the mycelium and the medium in which it is carried and preserved. Spawn
may be procured in the market in two forms, flake spawn and brick
spawn. In both forms the mycelium growth is started on a prepared medium
mainly consisting of manure and then arrested and dried. The flake spawn
is short-lived by reason of its loose form, in which the mycelium is
easily accessible to the air and destructive bacteria. It deteriorates
rapidly in transportation and storage and can only be used to advantage
when fresh. Growers, especially in the United States, have therefore
discarded it in favor of brick spawn, which affords more protection to
the mycelium and can be safely transported and stored for a reasonable
period.

Until recently the manufacturer of spawn was compelled to rely entirely
upon the caprice of nature for his supply. The only method known
consisted in gathering the wild spawn wherever nature had deposited it
and running the same into bricks or in loose material, without reference
to variety. Neither the manufacturer nor the grower had any means of
ascertaining the probable nature of the crop until the mushrooms
appeared.

[Illustration: Figure 503.--Agaricus villaticus.]

=PURE CULTURE SPAWN.=--The recent discovery of pure culture spawn in
this country has made possible the selection and improvement of
varieties of cultivated mushrooms with special reference to their
hardiness, color, size, flavor and prolificness, and the elimination of
inferior or undesirable fungi in the crop. The scope of this article
precludes a description of the pure culture method of making spawn. It
is now used by the large commercial growers and has in many sections
entirely superseded the old English spawn and other forms of wild spawn.
As now manufactured it resembles much in appearance the old English
spawn (see Figure 501). Some remarkable results have been obtained by
the use of pure culture spawn. We illustrate a cluster of fifty
mushrooms on one root grown by Messrs. Miller & Rogers, of Mortonville,
Pa., from "Lambert's Pure Culture Spawn" produced by the American Spawn
Company, of St. Paul, Minn. (Figure 502). Several promising varieties
have already been developed by the new method, and can now be reproduced
at will. Figure 503 is a good illustration of _Agaricus villaticus_, a
fleshy species in good demand. Figure 504 shows a bed of mushrooms grown
from pure culture spawn in a sand ro