horse-droppings, mingle with them some common road sand, place them under
cover, see that they are well beaten down in order to prevent
over-heating--turning them occasionally for the same purpose--and in due
time they will generate sufficient spores for a dozen mushroom beds of the
ordinary size. The reason for their appearance is the same as that
governing truffle spores--they come whenever conditions favor, that is,
whenever the soil is chemically balanced for their development and growth.
In other words, they come because it is just as impossible for them not to
come, in their proper environing conditions, as it is for the earth, in
its present cosmical relations, not to respond to its axial rotation. "Let
the earth bring forth" is just as much an outspoken law of nature, and one
as inexorably obeyed, as that unerring force of gravity which led
Leverrier, in the faith of his inductions, to indicate the precise point
in the heavens where the far-off planet, now bearing his name, might be
seen by the required telescope.

Dr. Cooke, quoting Mr. Cuthill's directions for producing mushroom spores,
says: "These little collections of horse-droppings and road sand, if kept
dry in shed, hole, or corner, under cover, will, in a short time, generate
plenty of spawn, and will be ready to spread on the surface of the bed in
early autumn." The collections should, of course, be made in the early
summer. But it is no part of our object to indicate, in this connection,
the process of truffle or mushroom culture. We merely refer to the methods
to show that the vital units, or germinal principles of life, in the case
of fungi, are just as dependent on "conditions" for their development, as
were the primordial germs of the gigantic cryptogams of the carboniferous
era. These primordial germs, or the _ZRA_ of the Bible genesis, must have
preceded the first fungous growth, as they preceded the first
spore-bearing cryptogam.