by fungi, which either completely destroy the tissue,
or alter its nature so much by the abstraction of the cellulose and
lignine, that it becomes loose and friable. Thus fungi induce the
rapid destruction of decaying wood. These are the conclusions
determined by Schacht, in his memoir on the subject.[Y]

We may allude, in passing, to another phase of destructiveness in the
mycelium of fungi, which traverse the soil and interfere most
injuriously with the growth of shrubs and trees. The reader of
journals devoted to horticulture will not fail to notice the constant
appeals for advice to stop the work of fungi in the soil, which
sometimes threatens vines, at others conifers, and at others
rhododendrons. Dead leaves, and other vegetable substances, not
thoroughly and completely decayed, are almost sure to introduce this
unwelcome element.

Living plants suffer considerably from the predations of parasitic
species, and foremost amongst these in importance are those which
attack the cereals. The corn mildew and its accompanying rust are
cosmopolitan, as far as we know, wherever corn is cultivated, whether
in Australia or on the slopes of the Himalayas. The same may also be
said of smut, for _Ustilago_ is as common in Asia and America as in
Europe. We have seen it on numerous grasses as well as on barley from
the Punjab, and a species different from _Ustilago maydis_ on the male
florets of maize from the same locality. In addition to this, we learn
that in 1870 one form made its appearance on rice. It was described as
constituting in some of the infested grains a whitish, gummy,
interlaced, ill-defined, thread-like mycelium, growing at the expense
of the tissues of the affected organs, and at last becoming converted
into a more or less coherent mass of spores, of a dirty green colour,
on the exterior of the deformed grains. Beneath the outer coating the
aggregated spores are of a bright orange red; the central portion has
a vesicular appearance, and is white in colour.[Z] It is difficult to
determine from the description what this so-called _Ustilago_ may be,
which was said to have affected a considerable portion of the standing
rice crop in the vicinity of Diamond Harbour.

Bunt is another pest (_Tilletia caries_) which occupies the whole
farinaceous portion of the grains of wheat. Since dressing the seed
wheat has been so widely adopted in this country, this pest has been
of comparatively little trouble. Sorghum and the