XI.
MOSSES.
By Dr. Braithwaite, F.L.S., etc.
In making a collection of the vegetable productions of a country we find considerable differences in the structure of the various groups of plants, and in the tissues of which they are composed; and hence special manipulation is requisite in dealing with certain orders. Some are of so succulent a nature, or have a framework so easily disintegrated, that they contain within themselves the elements of destruction, and present the greatest difficulty in satisfactory preservation, while others are so slightly acted on by external agents, that little trouble is required to prepare specimens of permanent beauty.
The Ferns and Lycopods, being generally appropriated by the collector of flowering plants, will be treated on with the latter, and following these come the Mosses, to which we will now direct attention, taking the alliance in its broadest sense, as including the three groups of Frondose Mosses, Bog Mosses, and Liver Mosses, or Hepaticæ, all of which are readily collected and preserved, and yield an endless fund of instructive entertainment to the microscopist. But it may be asked, Where is the game to be found? Where are the pleasant hunting-grounds in which they most do congregate? We answer, everywhere may some species or other be met with; yet, though many are cosmopolitan, the majority have their special habitats, and some their special seasons, both being considerably influenced by the presence of moisture.
Collecting.—The bryologist has one advantage over the phænogamous botanist, for it is not imperative that mosses should be laid out and pressed immediately; and hence less care is required in collecting them, than is bestowed on flowering plants; the necessary apparatus is confined to a pocket-knife, to remove specimens from stones or trees, a stock of stout waste paper, and a vasculum, or, better still, a strong bag, in which to carry the packets. When collecting the plants, it is well to remove any superfluous earth or stones, or to squeeze out the water from those found in bogs; and then each is to be wrapped separately in paper, and the locality marked outside; or the more minute species may, for greater safety, be placed in chip boxes. On reaching home, if we do not prepare the specimens at once, we must not leave the parcels packed together in their receptacle, or mould will soon attack them and spoil the whole; but we must spread them out on the floor until quite dry, and then reserve them to a convenient opportunity to lay out; as in the dry state they may be kept for years unchanged.
It often happens that our line of study is developed by some fortuitous circumstance. A neglected flowerpot in the corner of the garden attracts attention by its verdant carpet of moss, or, peeping over the wall, we see the crevices between the bricks bristling with capsules of Tortula muralis, the red twisted peristome freshly brought to view by the falling away of the lid, and, taking a bit indoors to submit to the microscope, we are so captivated therewith that we then and there determine to become a bryologist. Nor is this all that a journey round the garden will disclose: the neglected paths yield other species not less worthy of examination, and old apple-trees are not unfrequently tenanted by mosses.
Extending our walks to the commons, lanes, and woods, we may find on the ground and banks, in bogs and on the stumps and trunks of trees, a number of species greatly extending our list; while others again are only met with on the clay soil of stubble-fields, as various species of Pottia and Ephemerum: appearing in October, their delicate texture is developed by the constant moisture of winter, and with it also they vanish, to appear no more until the succeeding season. Travelling yet farther away, we find that each locality we visit yields some novelty: old walls and rocks of sandstone or slate, limestone districts, and, above all, a mountainous country, are rich in species we seek in vain elsewhere. Here peat bogs, and rocks dripping with water, ever supplied by the atmosphere, or the tumbling streams everywhere met with, are the chosen homes of these little plants, and thither must the collector resort, if he would reap his richest harvest. Winter and spring in the lowlands, and a later period in the elevated districts, will be found most productive of fruiting plants.
Preparation of Specimens.—So rapidly does the cellular texture of the mosses transmit fluid, that, when soaked in water, we see them swell up and expand their little leaves, and in a short time look as fresh as when growing; hence a basin of water, a towel, and drying-paper are all we require to prepare our specimens for the herbarium. If the tufts are large, we must separate them into patches sufficiently thin to lie flat, and by repeated washing, get rid of adherent earth, mud, or gravel. This is conveniently accomplished by holding the tuft in the palm of the hand, under a tap, and allowing a stream of water to pass through it; then by pressure in the folding towel we remove superfluous moisture and immediately transfer to paper, arranging the plants as we wish them to lie permanently, and placing with each a ticket bearing the name: a moderate weight is sufficient to dry them, as with great pressure the capsules split, and thus the value of the specimen is decreased. It not unfrequently happens that two or three species grow intermixed: these must be carefully separated at the time of soaking, and any capsules required to show the peristome must also be removed before the plants are submitted to pressure.