Fungals are among the lowest forms of vegetation, but in these we have peculiarities which appear to link them with the animal kingdom. Marcet found that mushrooms absorbed oxygen, and disengaged carbonic acid. In all probability this is only a chemical phenomenon of a precisely similar character to that which we know takes place with decaying wood. In the conversion of wood into _humus_, oxygen is absorbed, and combining with the carbon, it is evolved as carbonic acid. Of course we have the peculiar condition of vitality to modify the effect, and we have, too, in this class of plants, the existence of a larger quantity of nitrogen than is found in any other vegetating substance. These few sketches of remarkable phenomena connected with vegetation are intended to show merely the operations of the physical powers of the universe, so far as we know them, upon these particular forms of organization. During the process of germination, electricity is, according to Pouillet, evolved; and again, in ripening fruits, there appears to be some evidence of electrical currents. Vegetables are, however, in the growing state, such good conductors of electricity, that it is not, according to the laws of this force, possible that they should accumulate it; so that the luminous phenomena stated to have been observed cannot be due to this agency. We know, however, that under every condition of change, whether induced by chemical or calorific action, electricity is set in motion; and we have reasons for believing that the excitation of light will also give rise to electrical circulation. The question, whether plants possess sensation, whether they have any disposition of parts at all analogous to the nervous system of animals, has been often put forward, but as yet the answers have been unsatisfactory. The point is one well worthy all the attention of the vegetable physiologist; but regarding plants as the link between the animal and the mineral kingdom,--looking upon phyto-chemistry, as exhibited by them, as the means employed to produce those more complex organizations which exist in animals,--we necessarily consider plants as mere natural machines for effecting organic arrangements, and, as such, that they cannot possess any nervous sensibility. Muscular contraction may be represented in many of their marvellous arrangements; and any disturbance produced by natural or artificial means would consequently effect a change in the operations of those forces which combine to produce vegetable life. Indeed, the experiments of Carlo Matteucci, already referred to, prove that an incision across a leaf, the fracture of a branch, or the mere bruising of any part of the plant, interferes with the exercise of that power which, under the operation of luminous agency, decomposes carbonic acid, and effects the assimilation of the other elements.