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. 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