[Illustration: FIGURE 13.--Lepiota naucina. Spore print. (Natural
size.)]

But some may enquire how we know that there is any design in the
horizontal position of the cap, and that there is some cause which
brings about this uniformity of position with such entire harmony among
such dissimilar forms. When a mushroom with a comparatively long stem,
not quite fully matured or expanded, is pulled and laid on its side, or
held in a horizontal position for a time, the upper part of the stem
where growth is still taking place will curve upward so that the pileus
is again brought more or less in a horizontal position.

[Illustration: FIGURE 14.--Amanita phalloides. Plant turned to one side
by directive force of gravity, after having been placed in a horizontal
position. (Natural size.)]

In collecting these plants they are often placed on their side in the
collecting basket, or on a table when in the study. In a few hours the
younger, long stemmed ones have turned upward again. The plant shown in
Fig. 14 (_Amanita phalloides_) was placed on its side in a basket for
about an hour. At the end of the hour it had not turned. It was then
stood upright in a glass, and in the course of a few hours had turned
nearly at right angles. The stimulus it received while lying in a
horizontal position for only an hour was sufficient to produce the
change in direction of growth even after the upright position had been
restored. This is often the case. Some of the more sensitive of the
slender species are disturbed if they lie for only ten or fifteen
minutes on the side. It is necessary, therefore, when collecting, if one
wishes to keep the plants in the natural position for photographing, to
support them in an upright position when they are being carried home
from the woods.

The cause of this turning of the stem from the horizontal position, so
that the pileus will be brought parallel with the surface of the earth,
is the stimulus from the force of gravity, which has been well
demonstrated in the case of the higher plants. That is, the force which
causes the stems of the higher plants to grow upward also regulates the
position of the cap of the pileated fungi. The reason for this is to be
seen in the perfection with which the spores are shed from the surfaces
of the gills by falling downward and out from the crevices between. The
same is true with the shelving fungi on trees, etc., where the spores
readily fall out from the pores of the