experiments illustrating the reciprocal actions of different species of plants.  Various seeds were sprouted in water, in order to observe the nature of the excretions from their roots.  It was found “that the water in which plants of the family of the Leguminosae (beans and peas) grew acquired a brown color, from the substance which exuded from their roots.  Plants of the same species, placed in water impregnated with these excrements, were impeded in their growth, and faded prematurely; whilst, on the contrary, corn-plants grew vigorously in it, and the color of the water diminished sensibly, so that it appeared as if a certain quantity of the excrements of the Leguminosae had really been absorbed by the corn-plants.”  The oak, which is the great laboratory of tannin, not only lays up stores of it in its bark and leaves, but its roots discharge into the ground enough of it to tan the rootlets of all plants that venture to put down their suction-hose into the same region, and their spongioles are so effectually closed by this process, that they can no longer perform their office, and the plant that bears them dies.  Plants whose roots ramify among the roots of poppies become unwilling opium-eaters, from the exudation of this narcotic principle into the ground, and are stunted, like the children of Gin Lane.

The Aquarium furnishes a very interesting example of the mutual dependence of the three natural kingdoms.  Here, in a box holding a few gallons of water and a little atmospheric air, is a miniature world, secluded, and supplying its own wants.  Its success depends on the number and character of the animals and plants being so adapted as to secure just the requisite amount of active growth to each to sustain the life of the other:  that the plants should be sufficient to support, by the superfluities of their growth, the vegetarians among the animated tribes that surround them; and that all the animal tribes of the aquarium, whether subsisting upon the vegetables or on their smaller and weaker fellow-creatures, should restore to the water in excrements the mineral substances which will enable the plants to make good the daily loss occasioned by the depredations of the sea-rovers that live upon them.  Thus an aquarium, its constituents once correctly adjusted, has all the requisites for perpetuity; or rather, the only obstacle to its unlimited continuance is, that it is a mortal, and not a Divine hand, that controls its light and heat.

In the examination of the materials appropriated by plants from the soil, we find that mineral substances are sometimes taken up in solution in larger amount than the growth of the plant and the maturation of its fruit require, and the excess is deposited again, in crystalline form in the substance of the plant.  If we cut across a stalk of the garden rhubarb, we can see, with the aid of a microscope, the fine needle-shaped crystals of oxalate of potash lying among the fibres