now to be attained is not the formation of
fruit alone, but likewise its speedy desiccation and the prompt
dispersal of the perfected spores. Nothing can be more interesting than
to watch the slime-mould as its plasmodium accomplishes this its last
migration. If hitherto its habitat has been the soft interior of a
rotten log, it now begins to ooze out in all directions, to well up
through the crevices of the bark as if pushed by some energy acting in
the rear, to stream down upon the ground, to flow in a hundred tiny
streams over all the region round about, to climb all stems, ascend all
branches, to the height of many inches, all to pass suddenly as if by
magic charm into one widespread, dusty field of flying spores. Or, to be
more exact, whatever the position ultimately assumed, the plasmodium
soon becomes quiescent, takes on definite and ultimate shape, which
varies greatly, almost for each species. Thus it may simply form a flat,
cake-like mass, _aethalium_, internally divided into an indefinite
number of ill-defined spore cases, sporangia; or the plasmodium may take
the form of a simple net, _plasmodiocarp_, whose cords stand out like
swollen veins, whose meshes vary both in form and size; or more commonly
the whole protoplasmic mass breaks up into little spheroidal heaps which
may be sessile directly on the substratum, or may be lifted on tiny
stems, stipitate, which may rest in turn upon a common sheet-like film,
or more or less continuous net, spreading beneath them all, the
_hypothallus_. In any case, each differentiated portion of the
plasmodium, portion poorly or well defined, elongate, net-like,
spheroidal, elliptical, or of whatever shape, becomes at length a
sporangium, spore-case, receptacle for the development and temporary
preservation of the spores.[5]

The slime-moulds were formerly classed with the gasteromycetous fungi,
puff-balls, and in description of their fruiting phase the terms
applicable to the description of a puff-ball are still employed,
although it will be understood that the structures described are not in
the two cases homologous; analogous only. The sporangium of the
slime-mould exhibits usually a distinct _peridium_, or outer limiting
wall, which is at first continuous, enclosing the spores and their
attendant machinery, but at length ruptures, irregularly as a rule, and
so suffers the contents to escape. The peridium may be double, varies in
texture, color, persistence, and so forth