lar brick spawn would be removed two
generations from the natural spawn. So the number of times that
successive inoculations are made to multiply the spawn, the manufactured
products are removed that many generations from the natural spawn. Where
recourse is had to the natural, or virgin spawn only once in two years,
the second year's product would then be further removed from the natural
spawn than the first year's product. Where we know that it is removed
but one or a few generations from the natural spawn, it is a more
desirable kind. For the nearer it is to the natural spawn, other things
being equal, the more vigorous the mycelium, and the finer will be the
mushrooms produced.

The brick spawn is sometimes manufactured in this country by growers for
their own use, but at present it is manufactured on such a large scale
in England that little or no saving is effected by an attempt to
manufacture one's own brick spawn in this country.

=Flake Spawn.=--The flake spawn, or "flakes," is commonly known as the
French spawn, because it is so extensively manufactured in France. It is
made by breaking down beds through which the mycelium has run, and
before the crop of mushrooms appears. That is, the bed is spawned in the
ordinary way. When the mycelium has thoroughly permeated the bed, it is
taken down and broken into irregular pieces, six to eight inches in
diameter. Thus, the French spawn, where the beds are made entirely of
horse manure, with no admixture of soil, consist merely of the fermented
and cured manure, through which the mycelium has run, the material, of
course, being thoroughly dried. This spawn may be removed one or several
generations from the natural spawn.

[Illustration: FIGURE 234.--French spawn, or "flakes," ready to plant.]

The French growers depend on natural spawn much more than American
growers do. The natural spawn is collected from old manure heaps. Beds
made up in the ordinary way for the cultivation of mushrooms are planted
with this. The mycelium is allowed to run until it has thoroughly
permeated the manure. These beds are broken down and used to spawn the
beds for the crop. In this case the crop would be grown from spawn only
one generation removed from the virgin spawn. If a sufficient amount of
natural spawn could not be obtained, to provide the amount required one
generation old, it might be run through the second generation before
being used. From the appearance of any spawn, of cour