10,000 species, of which about 550 enter into the British Flora. These have spores free from spiral threads, which produce on germination a branched confervoid prothallium, the leaves undivided, consisting of uniform cells, the branches dichotomous or pinnate, the capsule opening usually by a lid and enclosing a spore sac.

2. SPHAGNINE, the Bogmosses, a limited group, having spores without spiral threads, which produce on germination a lichenoid prothallium, the leaves composed of two kinds of cells, the larger perforated and containing spiral fibres, the branches in lateral bundles of three to ten, the capsule sessile on a lateral naked branch.

3. HEPATICINE, the Liverworts, have spores with which are mixed elaters or spiral threads, producing a lichenoid prothallium, leaves nerveless, often lobed and furnished with stipules, or absent, and the whole plant resembling the thallus of a lichen; capsule without operculum splitting into four separate pieces, or sometimes two-valved, or clustered on a receptacle and opening by teeth.

We shall on the present occasion confine our attention solely to the frondose mosses, and pass in review the various organs revealed to us by the microscope. They have been called flowerless plants, but incorrectly, for we shall see that the reproductive organs though minute are very distinct, and their function is unmistakable; they are natives of every clime, and from sea-shore to the limit of perpetual snow are everywhere distributed, preferring, however, mountainous and woodland districts, because there is moisture most abundant; and for this reason also we find them most luxuriant in winter and spring, thus compensating for the absence of the more highly organised plants, which no sooner cover the surface of the earth than our little mosses are no longer noticed.

The denizens of the moss world are never found leading a solitary existence, but are either gregarious or more commonly densely aggregated into tufts or mats, which may contain hundreds of individuals; their size also is very variable, some species of Ephemerum not exceeding inch in height, while Polytrichum commune and some Hypnoid mosses attain a foot. We will take as our type the cosmopolitan Funaria hygrometrica, never absent from the ballast of our railway-banks, brick-fields, and heaths; and having carried home a tuft, let us expand it in water and detach a single plant.

VEGETATIVE SYSTEM.

First, we observe our Funaria has roots like all other mosses, and these probably not so much required for absorption as in

higher plants, but rather as a means of fixing the plants to the substratum on which they grow, for we find them on rocks and trunks of trees, where their chief support must be derived from the atmosphere; in very many species they occur not only at the base but also along the whole stem; sometimes these adventitious radicles are so dense that they mat the plants together into a spongy mass, and thus effectually retain a supply of moisture; the microscope shows us that each radicular fibril consists of a single series of cells, the transverse partitions of which are oblique. Then we see a short stem bearing leaves, with which also all mosses are supplied, and in this instance the fruit-stalk is a continuation of the stem-axis or is acrocarpic, any continued growth being by innovations or lateral repetitions of the stem; but in many mosses the fruit is lateral or pleurocarpic, and lateral branches are produced through a succession of years.

The leaves are attached horizontally, and are always sessile and persistent, their true arrangement being spiral; in Fissidens distichous or in two opposite rows (4) i.e. one spiral turn containing two leaves, in some tristichous () two spiral turns cutting through three leaves, and often five or eight rowed (3).

If we now tear off a few leaves from our Funaria, and place them in water between two slides and transfer to the microscope, we may learn a great deal about moss structure. First, as to the form of the leaf; this we observe is ovate, with the apex pointed, and the ovate or lanceolate form is the most common among the leaves of mosses, though we find every degree of expansion between orbicular and awl-shaped. Traversing the centre from base to apex is a midrib or nerve, composed of several layers of narrow cells; this in some species is altogether absent, in very many it vanishes about the middle or two-thirds the length of the leaf, while in others it is excurrent or extends beyond the leaf in a point, or it may be prolonged into a bristle or hair, and these by their number give the tufts of plants a woolly or hoary aspect. The margin is entire, but in many species it is variously toothed or serrated, and sometimes it has a thickened border. The lamina, or expanded plane of the leaf, is we observe composed of cells, by which a network is produced termed the areolation, and so constant are the individual cells in form and size, that a careful study of them is of the utmost importance in the identification of species, and indeed our only means of determining them when in a barren state.

In Funaria we find the surface is quite smooth, but in many species it is covered with papillæ; in none perhaps are these more evident than in the leaf of Thuidium tamariscinum,

which thus resembles a rasp.

In form the cells exhibit much variation, but they are referable to two types,

1. PARENCHYMATOUS when the ends are flattened, and we get a quadrate or hexagonal areolation as in Funaria; and, sometimes the cell walls are so thickened by internal deposit that their cavities appear like dots, as we see in Grimmia, Orthotrichum, Andreæa, etc.

2. PROSENCHYMATOUS when the transverse walls of the cells are oblique, so that the cells have pointed ends, as in Bryum, Hypnum, &c.

According to the quantity and tint of the chlorophyl contained in the cells will be the shade of colour of the plants; this is usually more or less green, but in Andreæa it is chocolate-brown or black, and some mosses are not unfrequently tinged with rosy purple or brown. The cells forming the leaf base are often of a different form from the upper cells, and when the leaves are closely imbricated they are thinner and usually empty; but those situated at the outer angles are sometimes very different from the rest, and then these alar cells become of value in the distinction of species and even of genera, as in Dicranum, for instance.

REPRODUCTIVE SYSTEM.

If we hunt up Funaria in December we shall find that instead of the long-stalked capsules the plants bear little rosettes of leaves, which are truly the flowers, and contain in their centre those reproductive organs, which even more clearly than stamens and pistils are necessary for the formation of fruit. The little starry heads at the end of the young lateral shoots are the male flowers, and by dissecting away the enveloping perigonial leaves in water we arrive at a cluster of finejointed threads or paraphyses, among which are little sausageshaped bodies, the antheridia, which at maturity give out a fluid containing excessively minute spiral threads, the spermatozoids; and it is to preserve the vitality of these that paraphyses are present, so as to keep up a certain amount of moisture; for the paraphyses are wanting in the closed bud-like flowers of Hypnum. If we look among the leaves terminating the stem we shall find similar female flowers also containing paraphyses, and longer and more slender bodies, archegonia, which are traversed by a fine channel, and open at maturity by a trumpet-shaped orifice, into which the spermatozoids pass, and reaching the germ cell in the base of the archegonium, this becomes fertilized and at once begins to develop into fruit.

In some mosses these two kinds of organs exist in one flower,

in others, as Funaria, the flowers are separate but on one plant, while in others they are on separate individuals; these three modifications constitute the synoicous, monoicous, and dioicous inflorescence.

As the germinative cell enlarges it pushes its way downward into the receptacle, and then increasing in diameter ruptures the membranous envelope of the archegonium, which is carried up on the rising fruit-stalk and becomes the calyptra, while an extension of the receptacle sheathes its base and is termed the vaginula. When the fruit-stalk has attained its full length its apex begins to enlarge and rapidly becomes moulded into the future fruit; if, when this is fully formed but still green, we make a vertical section of it, we see that the centre is occupied by a longitudinal bundle, the columella, between which and the capsule wall lies the sporangium or spore sac. inner wall of the spore sac is usually adherent to the columella, and its outer to the inner wall of the capsule, but both may be free as in Polytrichum, or the sporangium may be suspended from the capsule wall by threads as we see in Funaria, in which also the columella is very thick, and occupies a large portion of the cavity of the sporangium.

THE FRUIT.

The mature capsule or theca of mosses is at once the most striking and elegant part in these little plants, and never fails to excite the admiration of all who deign to notice them; the most elegant forms, adorned with the richest colours, are seen in the various groups, and these are still further enriched by the marvellous beauty often seen in the peristomes.

The thin membranous calyptra, often slit at the side by the distension of the fruit, is first thrown off, and we see the perfect capsule, furnished in most cases with an operculum or lid closing its mouth. The surface of the capsule is smooth and frequently furnished with stomata, well seen in the green fruit of Funaria; the cells composing the outer wall are of firm texture, and in Orthotricum and others in which striæ occur, these are formed of different shaped cells. In Splachnaceæ the neck of the capsule is swollen out into what is termed an apophysis. The forms of the capsule are infinitely varied, but spherical, ovate, pyriform and cylindric, are of most frequent

occurrence.

The operculum also presents various forms; in Funaria it is only a little convex, in many it is conical or obliquely rostrate, and its figure is very constant in individual species. Very frequently there is interposed between the mouth of the cap