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MOULDS. 157
its
power and limited its miscliief. Mouldy vetclies
and mouldy peas are, especially in moist seasons,
evils to wliicli the agriculturist
knows his crops to
be subject;
lie
may not know, however, that this
kind of mould (fig. 266) is of so near a kin to that
which has acquired such wide- spread fame in connection
with the potato. Another species of fungus
attacks the garden pea in damp seasons, forming
small depressed brownish spots on the leaves and
pods; but this is quite distinct from the mould,
though probably not less injurious.
The fertile threads are produced in dense clusters,
each many times branched, and bearing elliptic
acrospores obtuse at their apices,
and of a violaceous
tint (fig. 266). The oospores are beautifully reticulated
and of a yellowish-brown colour (plate X.
fig. 212).
Trefoil and some other allied plants are attacked
by another species, characterized by Dr. de Bary as
Peronospora trifoliorum,
which we have found rather
plentifully
in some localities on lucern.
The Paesnip Mould {Peronosjpora nivea, Ung.)
is found on many umbelUferous plants;
but its
attacks upon the parsnip are most to be deplored,
because it injures and ultimately destroys an article
of human food. The plants infested with this
parasite are first attacked in the leaves, but afterwards
the roots become spotted and diseased in a
similar manner to the potatoes attacked by its
congener. The disease has not hitherto been so