ampsora salicina_, Lev., are the winter fruits of _Lecythea
caprearum_, Lev., as those of _Melampsora populina_, Lev., are of
_Lecythea populina_, Lev. In the species of _Lecythea_ themselves will
be found, as De Bary[C] has shown, hyaline cysts of a larger size,
which surround the pseudospores in the pustules in which they are
developed.

A good illustration of dimorphism in one of the commonest of moulds is
given by De Bary in a paper from which we have already quoted.[D] He
writes thus:--In every household there is a frequent unbidden guest,
which appears particularly on preserved fruits, viz., the _mould_
which is called _Aspergillus glaucus_. It shows itself to the naked
eye as a woolly floccy crust over the substance, first purely white,
then gradually covered with little fine glaucous, or dark green dusty
heads. More minute microscopical examination shows that the fungus
consists of richly ramified fine filaments, which are partly
disseminated in the substratum, and partly raised obliquely over it.
They have a cylindrical form with rounded ends, and are divided into
long outstretched members, each of which possesses the property which
legitimatizes it as a vesicle in the ordinary sense of the word; it
contains, enclosed within a delicate structureless wall, those bodies
which bear the appearance of a finely granulated mucous substance,
which is designated by the name of protoplasm, and which either
equally fills the cells, or the older the cell the more it is filled
with watery cavities called vacuoles.

All parts are at first colourless. The increase in the length of the
filaments takes place through the preponderating growth near their
points; these continually push forward, and, at a short distance from
them, successive new partitions rise up, but at a greater distance,
the growth in the length ceases. This kind of growth is called point
growth. The twigs and branches spring up as lateral dilatations of
the principal filament, which, once designed, enlarges according to
the point growth. This point growth of every branch is, to a certain
extent, unlimited. The filaments in and on the substratum are the
first existing members of the fungus; they continue so long as it
vegetates. As the parts which absorb nourishment from and consume the
substance, they are called the _mycelium_. Nearly every fungus
possesses a mycelium, which, without regard to the specific difference
of form and size, especially shows the de