Certainly the whole subject is of sufficient importance to demand the
careful study of competent observers.
* * * * *
THE GUM DISEASE IN TREES.[1]
[Footnote 1: Communicated to the _Medical Times_ by Sir James Paget.]
An essay by Dr. Beijerinck, on the contagion of the gum disease in
plants, lately published by the Royal Academy of Sciences at
Amsterdam, contains some useful facts. The gum disease (_gummosis,
gum-flux)_ is only too well known to all who grow peaches, apricots,
plums, cherries, or other stone fruits. A similar disease produces gum
arabic, gum tragacanth, and probably many resins and gum resins. It
shows itself openly in the exudation of thick and sticky or hard and
dry lumps of gum, which cling on branches of any of these trees where
they have been cracked or wounded through the bark. Dr. Beijerinck was
induced to make experimental inoculations of the gum disease by
suspicions that, like some others observed in plants, it was due to
bacteria. He ascertained that it is in a high degree contagious, and
can easily be produced by inserting the gum under the edge of a wound
through the bark of any of the trees above named. The observation that
heated or long boiled pieces of gum lose their contagious property
made it most probable that a living organism was concerned in the
contagions; 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.
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