_Saprolegniei_ be excluded. In _Botrytis_ and in
_Polyactis_, the flocci and spores are similar, but the branches of
the threads are shorter and more compact, and the septa are more
common and numerous; the oogonia also are absent. De Bary has selected
_Polyactis cinerea_, as it occurs on dead vine leaves, to illustrate
his views of the dualism which he believes himself to have discovered
in this species. "It spreads its mycelium in the tissue which is
becoming brown," he writes, "and this shows at first essentially the
same construction and growth as that of the mycelium filaments of
_Aspergillus_." On the mycelium soon appear, besides those which are
spread over the tissue of the leaves, strong, thick, mostly
fasciculate branches, which stand close to one another, breaking forth
from the leaf and rising up perpendicularly, the conidia-bearers. They
grow about 1 _mm._ long, divide themselves, by successively rising
partitions, into some prominent cylindrical linked cells, and then
their growth is ended, and the upper cell produces near its point
three to six branches almost standing rectangularly. Of these the
under ones are the longest, and they again shoot forth from under
their ends one or more still shorter little branches. The nearer they
are to the top, the shorter are the branches, and less divided; the
upper ones are quite branchless, and their length scarcely exceeds the
breadth of the principal stem. Thus a system of branches appears, upon
which, on a small scale, a bunch of grapes is represented. All the
twigs soon end their growth; they all separate their inner space from
the principal stem, by means of a cross partition placed close to it.
All the ends, and also that of the principal stem, swell about the
same time something like a bladder, and on the upper free half of each
swelling appear again, simultaneously, several fine protuberances,
close together, which quickly grow to little oval bladders filled with
protoplasm, and resting on their bearers with a sub-sessile,
pedicellate, narrow basis, and which at length separate themselves
through a partition as in _Aspergillus_. The detached cells are the
conidia of our fungus; only one is formed on each stalk. When the
formation is completed in the whole of the panicle, the little
branches which compose it are deprived of their protoplasm in favour
of the conidia; it is the same with the under end of the principal
stem, the limits of which are marked by a cro