ons; and he then found that only those pieces of the gum
conveyed contagion in which, whether with or without bacteria, there
were spores of a relatively highly organized fungus, belonging to the
class of Ascomycetes; and that these spores, inserted by themselves
under the bark, produced the same pathological changes as did the
pieces of gum. The fungus thus detected, was examined by Professor
Oudemans, who ascertained it to be a new species of Coryneum, and has
named it _Coryneum Beijerincki_. The inoculation experiments are best
made by means of incisions through the bark of young branches of
healthy peach trees or cherry trees, and by slightly raising the cut
edge of the bark and putting under it little bits of gum from a
diseased tree of the same kind. In nearly every instance these wounds
become the seats of acute gum disease, while similar wounds in the
same or other branches of the same tree, into which no gum is
inserted, remain healthy, unless, by chance, gum be washed into them
during rain. The inoculation fails only when the inserted pieces of
gum contain no Coryneum. By similar inoculations similar diseases can
be produced in plum, almond, and apricot trees, and with the gum of
any one of these trees any other can be infected; but of many other
substances which Beijerinck tried, not one produced any similar
disease. The inoculation with the gum is commonly followed by the
death of more or less of the adjacent structures; first of the bark,
then of the wood. Small branches or leaf stalks thus infected in
winter, or in many places at the same time, may be completely killed;
but, in the more instructive experiments the first symptom of the gum
disease is the appearance of a beautiful red color around the wound.
It comes out in spots like those which often appear spontaneously on
the green young branches of peach trees that have the gum disease; and
in these spots it is usual to find Coryneum stromata or mycelium
filaments. The color is due to the formation of a red pigment in one
or more of the layers of the cells of the bark. But in its further
progress the disease extends beyond the parts at which the Coryneum or
any structures derived from it can be found; and this extension,
Beijerinck believes, is due to the production of a fluid of the nature
of a ferment, produced by the Coryneum, and penetrating the adjacent
structures. This, acting on the cell walls, the starch granules, and
other constituents of the ce