dissolved, animalcules or mites make their appearance, till at last the whole becomes a loathsome mass of putrescence.” The form of the mould itself is represented (fig. 264) as exhibited under the microscope, with the nodose swellings of the branches, and spores attached to the tips. These acrospores are filled with a granular mass, from which, as hereafter described, zoospores are produced. The branching dendroidal threads of this fungus proceed from a creeping mycelium or spawn of entangled filaments which interpenetrates the matrix, upon which it establishes itself. Upon these threads spherical bodies were long since observed by Dr. Payen, and, under the name of _Artotrogus_, described by Dr. Montagne as a new species of fungus. Dr. de Bary failed to detect oospores on the mycelium of this mould, although the organs found by Payen in some sort resemble them. De Bary sought in vain, also, for the spherical bodies described by the author above named. It has been calculated that one square line of the under surface of the leaves is capable of producing 3,270 acrospores, each of which yields at least six zoospores, sometimes double that number; thus we have 19,620 reproductive bodies from that small space. The mycelium from the zoospores is capable of penetrating the cellular tissue in twelve hours, and, when established there, it bursts through the stomata of the leaves, and fruit is perfected in from fifteen to eighteen hours. Since the zoospores are perfected and ready to germinate in twenty-four hours from their being placed in water, it becomes almost impossible to calculate the myriads of fungi that may be produced from a single centre. Dr. de Bary has also demonstrated that the brown spots so characteristic of the disease are the result of the action of the spores or zoospores. By placing a quantity of spores in a drop of water on the leaves, stems, and tubers under a glass sufficiently air-tight to prevent evaporation, he produced the brown spots, and traced their progress from the earliest stages.