able
movement of retraction, then the ascus returned again, immediately
towards its previous limits, always with a reduction in the number of
its contained sporidia.

The dehiscence of the asci takes place in the _Ascobolei_, in some
species of _Peziza_, _Morchella_, _Helvella_, and _Verpa_, by means of
an apical operculum, and in other _Pezizae_, _Helotium_, _Geoglossum_,
_Leotia_, _Mitrula_, &c., by a fissure of the ascus. This operculum
may be the more readily seen when the ascus is coloured by a drop of
tincture of iodine.

The sporidia are usually four or eight, or some multiple of that
number, in each ascus, rarely four, most commonly eight. At a fixed
time the protoplasm, which at first filled the asci, disappears or is
absorbed in a mucilaginous matter, which occupies its place, in the
midst of which is a small nucleus, which is the rudiment of the first
spore; other spores are formed consecutively, and then the substance
separates into as many sections as there are sporidia. From this
period each sporidium seems to have a separate existence. All have a
nucleus, which is scarcely visible, often slightly granular, but which
is quite distinct from the oleaginous sporidioles so frequent amongst
the Discomycetes, and which are sometimes called by the same name. The
sporidia are at first a little smaller than when mature, and are
surrounded by mucilage. After this period the sporidia lose their
nebulous granulations, whilst still preserving their nucleus; their
outlines are distinct, and, amongst the true _Ascobolei_, commence
acquiring a rosy colour, the first intimation of maturity. This colour
manifests itself rapidly, accumulating exclusively upon the epispore,
which becomes of a deep rose, then violet, and finally violet blue, so
deep as sometimes to appear quite black. There are some modifications
in this coloration, since, in some species, it passes from a vinous
red to grey, then to black, or from rose-violet to brown.

The epispore acquires a waxy consistence by this pigmentation, so that
it may be detached in granules. It is to this particular consistency
of the epispore that the cracks so frequent in the coloured sporidia
of _Ascobolus_ are due, through contraction of the epispore. As they
approach maturity, the sporidia accumulate towards the apex of the
asci, and finally escape in the manner already indicated.

In all essential particulars there is a great similarity in the
structure of the other Di