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114 MICEOSCOPIC ruxGi.
obtrusive of the dust-like fungi. It is not confined
to roses ;
but the meadow- sweety on which it is
also found, does not grow
parasite is
in localities where its
so liable to meet the gaze of the ordinarywayfarer.
The habit of this rust is more or less
that of those which are associated with it. The
pustules are not small and orbicular as in most
instances in other groups (except Polycystis), but
are large and irregular_,
and generally but few
together or single. The spores are variously coloured_,
and have peduncles, or footstalks, of a
greater or less length. In the rose rust these
spores are profuse, but the peduncle is short (plate
YII. fig. 148).
Plants of the pea and bean tribe are Hable to
be attacked by one of these rusts, and in this instance
the spores are so characteristic that no one
could well confound them with any other. Externally
it appears as an irregular brownish pustule,
breaking through the epidermis and filled with an
impalpable powder, not unlike a pinch of ^' brown
rappee '' snufi". The spores are ovoid, with a verylong
peduncle, whence its name {Uromyces appencliculata).
It appears on a great variety of plants, but
from the peculiarity of the spores (plate YII. fig.
150), is easily recognized. Our figure represents
it on the leaf of a vetch (plate YII. fig. 149).
Almost at the commencement of this volume
(Chap. III.) we had occasion to refer in detail to
some experiments made by De Bary on the spores