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347
In consequence of the microscopie minuteness of the spores their
volume and weight is very small as compared with the size of
their surface, and from this reason they are exceedingly sensitive
to air movements. Everybody who has laid the cap of a mush-
room on a paper for collecting the falling spores knows that even
in a room, the doors and windows of which are fully closed, so
that there is a practical stillness of the air, the spores do not drop
right vertically but sail like a down more or less sidewise so that
the deposited spores give only a blurred picture of the gills or
pores or spines unless a small dish or the like is placed bottom
up over the fungus so as to still more prevent movements of the
air surrounding the dropping spores.
From this we understand that the wind will catch the falling
spores and bring them far away from their native place, and that
the thick and uniform spore layer covering the upper side of Pol.
applanatus etc. thus can not have been deposited during wind but
only in calm or nearly calm weather.
It is perhaps not unreasonable to suppose that from the ground
heated during a hot day arise during a following cold and calm
night upwardly directed air currents, which, though very feeble and
perhaps not perceptible to our senses, yet are strong enough to
force the falling spores upwards, so that these are caused to hover
in the air above their native place a more or less long while ere
they are allowed to fall again and land on the upper side of objects
lying in their way.
With such a supposition the occurrence on the upper side of
Polypori and other Hymenomycetes of spores exactly like those
generated in the hymenium on the underside of said fungi is conceivable
without resorting to the »conidia»-theory. Such a supposition ex-
plains also the occurrence of said spores on adjacent or superposed
objects, which is incomprehensible, if we adhere to said theory.
Here some one might remark: if the spores are so light and easily
moved even by the slightest movement of the air, why do they
remain on the object, where they land, and are not blown away
by the first next breeze?
The answer is: the living spores adhere pertinaciously to the
surface with which they come into contact. Ash or other dry
powder strewed on a dry glass-plate you can easily blow away,
but if you catch on the same glass-plate the spores dropping from
a mushroom, you are unable to remove them by blowing. I do
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