The Book of Household Management by Mrs. Beeton

the vegetable ends, it is as difficult to account for many of the singularities by which numbers of plants are characterized. This, however, can hardly be regarded as a matter of surprise, when we recollect that, so far as it is at present known, the vegetable kingdom is composed of upwards of 92,000 species of plants. Of this amazing number the lichens and the mosses are of the simplest and hardiest kinds. These, indeed, may be considered as the very creators of the soil: they thrive in the coldest and most sterile regions, many of them commencing the operations of nature in the growth of vegetables on the barest rocks, and receiving no other nourishment than such as may be supplied to them by the simple elements of air and rain. When they have exhausted their period in such situations as have been assigned them, they pass into a state of decay, and become changed into a very fine mould, which, in the active spontaneity of nature, immediately begins to produce other species, which in their turn become food for various mosses, and also rot. This process of growth and decay, being, from time to time, continued, by-and-by forms a soil sufficient for the maintenance of larger plants, which also die and decay, and so increase the soil, until it becomes deep enough to sustain an oak, or even the weight of a tropical forest. To create soil amongst rocks, however, must not be considered as the only end of the lichen; different kinds of it minister to the elegant arts, in the form of beautiful dyes; thus the _lichen rocella_ is used to communicate to silk and wool, various shades of purple and crimson, which greatly enhance the value of these materials. This species is chiefly imported from the Canary Islands, and, when scarce, as an article of commerce has brought as much as £1000 per ton.