Remarking the great similarity of appearance between the substance of mushrooms and the muscular fibre, he wished to ascertain whether they possessed a similar power of contraction. He accordingly made a considerable number of experiments, from which he concluded that the different kinds of mushrooms, which in becoming putrid emit an animal insipid cadaverous smell, are as perfect conductors in the Galvanic chain as the organs of animals. His experiments likewise proved that they possessed irritability. Mr. Humboldt afterwards directed his inquiries to the _manner_ in which Galvanism acted upon the irritable fibre, which, as we have already mentioned, he first observed. These experiments, however, were unsuccessful. We shall not therefore relate them. The effects of Galvanism on vegetation are supposed to be deleterious, as will appear from the following extract from the “Monthly Magazine.” “It often happens, that some of the limbs of fruit trees, trained against a wall, are blighted and die; while others remain in a healthy and flourishing state. This evil is, by gardeners, generally attributed to the effects of lightning. But, if this were the case, would not the violent action of the electric fluid produce a laceration of the branch and stalk of the tree? No such effect is to be perceived. It therefore appears to me, that we must seek some other cause for this evil, and I flatter myself that I have discovered the real one. A few years since, when Galvanism was first introduced to public notice, I constructed a pile, consisting of about one hundred plates of copper and as many of zinc, each about two inches square. Among other experiments, I applied it to the branch of a tender plant, (a species of the ficoides.) Having left it for about an hour, on my return I found the branch withered, and hanging close to the stalk. It immediately occurred to me, that Galvanism might be the cause of the above mentioned defect in wall fruit trees, occasioned by the oxydation of the nails, by which they are oftentimes fastened (for I conceive Galvanism to be produced, in a greater or less degree, by every metal passing into a state of oxydation.) Recollecting that the limb of a cherry tree in my garden had, nearly a year before, been fastened to the wall with an iron cramp, I instantly examined it, and found it dead; though, when fastened, it was a flourishing, healthy limb, at least an inch in diameter, and nine feet in length.