Fig. 302.—Section of leaf of Sphagnum moss, showing large cells of spiral fibres and connecting apertures.
Mosses, like liverworts, possess both antheridia and pistillida, which are engaged in the process of fructification. The fertilized cell becomes gradually developed into a conical body elevated upon a footstalk, the walls of the flask-shaped body carrying the higher part upwards as a calyptra or hood upon its summit, while the lower part remains to form a kind of collar round the base. These spore-capsules are closed on their summit by opercula or lids, and their mouths when laid open are surrounded by a beautiful toothed fringe, termed the peristome. This fringe is shown in [Fig. 303], in the centre of a capsule of Funaria, with its peristome in situ. The fringes of teeth are variously constructed, and are of great service in discriminating the genera. In Neckera antipyretica the peristome is double, the inner being composed of teeth united by cross bars, forming a very pretty trellis. The seed spores are contained in the upper part of the capsule, where they are clustered round the central pillar, termed the columella; and at the time of maturity, the interior of the capsule is almost entirely occupied by spores.
Fig. 303.—Mouth of Capsule of Funaria, showing Peristome.
Fig. 304.—Hair-moss in Fruit.
The undulating hair-moss, Polytrichum undulatum ([Fig. 304]), is found on moist, shady banks of pools and rivulets. The seed-vessel has a curious shaggy cap; but in its construction it is very similar to that of the screw-moss, except that the fringe around its opening is not twisted. The reproductive organs of mosses are of two kinds; the capsule containing minute spores, archegonia, and the antheridia, or male efflorescence. The capsule, theca, or sporangium, is lateral or terminal, sessile, or on a fruit stalk (seta) of various shapes, indehiscent, or bursting by four valves at the sides, or more commonly by a deciduous cup, operculum. When this falls the mouth of the capsule becomes exposed. The rim is crowned with tooth-like or cilia-like appendages in sets of four or multiples of that number—peristome. These are often brightly coloured and hydroscopic. By simply breathing upon them they suddenly fly open, and are endowed with motion, that is, if they contain spores. The spores on germination produce a green confervoid-like mass of threads, from which the young plant arises.
The Sphagnaceæ, or “bog mosses,” have been separated from true mosses from the marked differences they present. The stem is more widely differentiated, and throughout its structure a rapid passage of fluid takes place. It has the power of absorbing moisture from the atmosphere, so that if a plant be placed dry in a glass of water with its rosette of leaves hanging over the edge, it acts like a syphon, and the water will drop from it until the glass is emptied. As may be supposed, the leaf is composed of large open cells, and it absorbs more water than the root. The antherids or male organs of Sphagnaceæ resemble those of liverworts, rather than those of mosses, both in form and arrangement; they are grouped in “catkins” at the tips of the lateral branches, each of the imbricated perigonal leaves enclosing a single globose antherid on a slender foot-stalk, and surrounded by long branched paraphyses of cobweb-like tenuity. The female organs, or archegones, do not differ materially in structure from those of mosses; they are grouped together in a sheath of deep green leaves at the end of the shorter lateral branchlets at the side of the rosette or terminal crown of leaves. The sporange is very uniform in all the species, and the spores are in groups of fours, as in mosses, around a hemispherical columella. These plants grow so rapidly that they soon cover a pool with thin matted bundles of branches, and as they decay they fall to the bottom, and become the foundation of the future bog or peat moss.
Felices.—Of all the spore-bearing families the ferns are the more universally known. They constitute an exceedingly numerous genera and species, and vary from low herbaceous plants of an inch in height to that of tree ferns, which attain a height of fifty or more feet, terminating in a graceful coronet of fronds or leaves. Of whatever size a fern may be, its spores are, for the most part, microscopic, produced within the sporangium by cell division, and are therefore free and variously shaped.