bright tints. In the _Mucedines_, on the contrary,
the threads are never coated, seldom dingy, mostly white or of pure
colours, and the spores have less a tendency to extra development or
multiplex septation. In some genera, as in _Peronospora_ for
instance,[P] a secondary fruit is produced in the form of resting
spores from the mycelium; and these generate zoospores as well as the
primary spores, similar to those common in _Algae_. This latter genus
is very destructive to growing plants, one species being the chief
agent in the potato disease, and another no less destructive to crops
of onions. The vine disease is produced by a species of _Oidium_,
which is also classed with _Mucedines_, but which is really the
conidiiferous form of _Erysiphe_. In other genera, the majority of
species are developed on decaying plants, so that, with the exception
of the two genera mentioned, the _Hyphomycetes_ exert a much less
baneful influence on vegetation than the _Coniomycetes_. The last
section, including the _Sepedoniei_, has been already cited as
remarkable for the suppression of the threads, which are scarcely to
be distinguished from the mycelium; the spores are profuse, nestling
on the floccose mycelium; whilst in the _Trichodermacei_, the spores
are invested by the threads, as if enclosed in a sort of false
peridium. A summary of the characters of the family may therefore be
thus briefly expressed:--

_Filamentous; fertile threads naked, for the most part free or loosely
compacted, simple or branched, bearing the spores at their apices,
rarely more closely packed, so as to form a distinct common stem_ =
HYPHOMYCETES.

[Illustration: FIG. 40.--_Rhopalomyces candidus._]

Having thus disposed of the _Sporifera_, we must advert to the two
families of _Sporidiifera_. As more closely related to the _Hyphomycetes_,
the first of these to be noticed is the _Physomycetes_, in which there
is no proper hymenium, and the threads proceeding from the mycelium bear
vesicles containing an indefinite number of sporidia. The fertile threads
are either free or only slightly felted. In the order _Antennariei_, the
threads are black and moniliform, more or less felted, bearing irregular
sporangia. A common fungus named _Zasmidium cellare_, found in cellars,
and incrusting old wine bottles, as with a blackened felt, belongs to
this order. The larger and more highly-developed order, _Mucorini_,
differs in the threads, which are simple or branch