loam preventive, I have tried
it lightly and heavily, but without any apparent good effect.

=Black Spot.=--All mushroom growers are familiar with this disease, but
unless it appears in pronounced form very little notice is taken of it,
even by market men, for we see spotted mushrooms continually exposed for
sale. It appears as dark brown spots, streaks, or freckles, on the top
of the mushroom caps, and increases in distinctness and breadth with
age. Fig. 25. It is caused by eel worms (_Anguillulae_). These minute
creatures enter the mushrooms when the latter are in their tiniest pin
form and before they emerge from the ground. If a button arises clean it
remains clean, if diseased it continues to be diseased, and it is a
fact that if one mushroom in a clump has black spot we usually find that
every mushroom in the clump has it. But mushrooms growing from the same
bit of spawn and that come up an inch or two away from the spotted ones
may be perfectly clean. Black spot has never occurred with me in new
beds, and seldom in those in vigorous bearing, but it generally appears
in beds that have been in bearing condition for some weeks or are
declining. It does not confine itself to any particular spot or part of
the bed, and sometimes it is much more plentiful than at others. Between
October and March we have very little black spot, but as the spring
opens this disease increases. During the winter season, with careful
attention, perhaps not so much as one per cent will show black spot, but
as the warm weather sets in the per centage increases until in May, when
as many as twenty per cent may be affected by it.

[Illustration: FIG. 25. MUSHROOM AFFECTED WITH BLACK SPOT.]

Black spot is a disease, however, that can be controlled. Keep
everything in and about the mushroom houses rigidly clean, and as soon
as a bed has ceased to bear a crop worth picking clear it out, lime-wash
the place it occupied, and make up another bed. Carefully observe that
no old loam or manure is allowed to accumulate anywhere, or green scum
forms upon the boards, paths, or walls; boiling water impregnated with
alum poured over the boards, walls, and other scum-covered surfaces,
will kill the eel worms, but it should not be allowed to touch the
mushroom beds that are in bearing or coming into bearing. Much can be
done to protect the bearing beds from the ravages of this pest: In
gathering the mushrooms remove every vestige of old stump and fogged-off