ns have been proposed
for the growth of such conditions as the cells which induce
fermentation, to which yeast plants belong. A fly attacked by _Empusa
muscae_, if immersed in water, will develop one of the _Saprolegniae_.

The _Uredines_ and other epiphyllous _Coniomycetes_ will readily
germinate by placing the leaf which bears them on damp sand, or
keeping them in a humid atmosphere. Messrs. Tulasne and De Bary have,
in their numerous memoirs, detailed the methods adopted by them
for different species, both for germination of the pseudospores and
for impregnating healthy foster plants. The germination of the
pseudospores of the species of _Podisoma_ may easily be induced, and
secondary fruits obtained. The germination of the spores of _Tilletia_
is more difficult to accomplish, but this may be achieved. Mr.
Berkeley found no difficulty, and had the stem impregnated as well as
the germen. On the other hand, the pseudospores of _Cystopus_,
when sown in water on a slip of glass, will soon produce the
curious little zoospores in the manner already described.

The sporidia of the _Discomycetes_, and some of the _Sphaeriacei_,
germinate readily in a drop of water on a slip of glass, although not
proceeding further than the protrusion of germ-tubes. A form of slide
has been devised for growing purposes, in which the large covering
glass is held in position, and one end of the slip being kept immersed
in a vessel of water, capillary attraction keeps up the supply for an
indefinite period, so that there is no fear of a check from the
evaporation of the fluid. Even when saccharine solutions are employed
this method may be adopted.

The special cultivation of the _Peronosporei_ occupied the attention
of Professor De Bary for a long time, and his experiences are
detailed in his memoir on that group,[O] but which are too long
for quotation here, except his observations on the development of the
threads of _Peronospora infestans_ on the cut surface of the tubers
of diseased potatoes. When a diseased potato is cut and sheltered from
dessication, the surface of the slice covers itself with the mycelium
and conidiiferous branches of _Peronospora_, and it can easily be
proved that these organs originate from the intercellulary tubes of
the brown tissue. The mycelium that is developed upon these slices
is ordinarily very vigorous; it often constitutes a cottony mass of a
thickness of many millimetres, and it gives out conidiiferous