both are obliterated, so that there is no peristome at all. The number of the "teeth" is always a multiple of 4, varying from 4 to 64; sometimes they are prolonged into straight or twisted hairs. The spores are contained in the upper part of the capsule, where they are clustered round a central pillar, which is termed the columella. In the young capsule, the whole mass is nearly solid (Fig. 135, c), the space (7) in which the spores are developed being very small; but this gradually augments, the walls becoming more condensed; and at the time of maturity, the interior of the capsule is almost entirely occupied by the spores, in the dispersion of which the peristome seems in some degree to answer the same purpose as the elaters of Hepatica. The development of the spores into new plants, commences with the rupture of their outer walls, and a protrusion of their inner coats; and from the projecting extremity new cells are put forth by a process of outgrowth, which form a sort of confervoid filament (as in Fig. 145, c). At certain points of this filament, its component cells multiply by subdivision, so as to form rounded clusters, from every one of which an independent plant may arise; so that several individuals may be evolved from a single spore. A numerous aggregation of spores may be developed, as we have seen, from a single germ-cell; so that the immediate product of each act of fertilization does not consist (as in the higher Plants) of a single seed, that afterwards developes itself into a composite fabric, whence are put forth a multitude of leaf buds, every one of which is capable (under favorable circumstances) of evolving itself into a complete Plant; but divides itself at once into a mass of isolated cells (spores), of which every one may be considered in the light of a bud or gemma of the simplest possible kind, and one of the first acts of which is to put forth other buds,

FIG. 140.

whereby the rapid extension of these plants is secured, although no separate individual ever attains more than a very limited size.

218. In the Ferns we have in many respects a near approximation to Flowering plants; but this approxima tion does not extend to their Reproductive apparatus, which is formed upon a type essentially the same as that of Mosses, but is evolved at a very different period of life. As the component tissues of which their fabrics are composed, are essentially the same as those Oblique section of footstalk of Fern- which will be described in the next chapleaf, showing bundle of scalariform ducts. ter, it will not be requisite here to dwell upon them. The stem (where it exists) is for the most part made up of cellular parenchyma, which is separated into a cortical and a medullary portion, by the inter

position of a circular series of fibro-vascular bundles containing true woody tissue and ducts. These bundles form a kind of irregular network, from which prolongations are given off that pass into the leaf-stalks, and thence into the midrib and its lateral branches; and it is their peculiar arrangement in the leafstalks, which gives to the transverse section of these the figured marking commonly known as "King Charles in the oak." A thin section, especially if somewhat oblique (Fig. 140), displays extremely well the peculiar character of the

.

ducts of the Fern; which are termed "scalariform," from the resemblance of the regular markings on their walls to the rungs of a ladder. What is usually considered the "fructification" of the Ferns, affords a most beautiful and readily prepared class of opaque objects for the lowest powers of the Microscope; nothing more being necessary, than to lay a fragment of the frond that bears it on its under surface, upon the glass stage-plate, or to hold it in the stage-forceps, and to throw an adequate light upon it by the side-condenser. It usually presents itself in the form of isolated spots, termed sori, as in the common Polypodium (Fig. 141), and in the Aspidium (Fig. 143); but sometimes these "sori" are elongated into bands, as in the common Scolopendrum (Harts tongue): and these bands may coalesce with each other, so as almost to cover the surface of the frond with a network, as in Hamionites (Fig. 142); or they may form merely a single band along its borders, as in the common Pteris (brake-fern). The sori are sometimes naked on the under surface of the fronds;

but they are frequently covered with a delicate membrane, termed the indusium, which may either form a sort of cap upon the summit of each sorus, as in Aspidium (Fig. 143), or a long fold, as in Scolopendrum and Pteris, or a sort of cup, as in Deparia (Fig. 144). Each of these sori, when sufficiently magnified, is found to be made up of a multitude of capsules or theca (Figs. 143, 144), which are sometimes closely attached to the surface of the leaf, but more commonly spring from it by a pedicel or footstalk. The wall of the capsule is composed of flattened cells, applied to each other by their edges; but there is generally one row of these, thicker and larger than the rest, which springs from the pedicel, and is continued over the summit of the capsule, so as to form a projecting ring, which is known as the annulus. This ring has an elasticity superior to that of all the rest of the capsular wall, causing it to split across, when mature, so that the contained spores may escape; and in many instances carrying the two halves of the capsule widely apart from each other (Fig. 141), the fissure extending to such a depth as to separate them completely. It will frequently happen, that specimens of Fernfructification gathered for the Microscope, will be found to have all the capsules burst and the spores dispersed, whilst in others, less advanced, the capsules may all be closed; others, however, may often be met with, in which some of the capsules are closed and others are open; and if these be watched with sufficient attention, the rupture of some of the thecæ and the dispersion of the spores may be observed to take place, whilst the specimen is under observation in the field of the microscope. In sori whose capsules have all burst, the annuli connecting their two halves are the most conspicuous objects, looking, when a strong light is thrown upon them, like strongly banded worms of a bright brown hue. This is particularly the case in Scolopendrum,

Sorus and cup-shaped indusium of Deparia prolifera.

whose elongated sori are remarkably beautiful objects for the microscope in all their stages; until quite mature, however, they need to be brought into view by turning back the two indusial folds that cover them. The commonest Ferns, indeed, which are found in almost every hedge, furnish objects of no less beauty

than those yielded by the rarest exotics; and it is in every respect a most valuable training to the young, to teach them how much there may be found to interest, when looked for with intelligent eyes, even in the most familiar and therefore disregarded specimens of Nature's handiwork.

219. The spores (Fig. 145, A) set free by the bursting of the thecæ, usually have a somewhat angular form, and are invested by a yellowish or brownish outer coat, which is marked, very much in the manner of pollen-grains (Fig. 187), with points, streaks, ridges, or reticulations. When placed upon a damp surface, and exposed to a sufficiency of light and warmth, the spore begins to "germinate," the first indication of its vegetative activity being a slight enlargement, which is manifested in the

FIG. 145.

B

Development of Prothallium of Pteris serrulata :—A, spore set free from the theca;-B, spore beginning to germinate, putting forth the tubular prolongation a from the principal cell, b;-c, first formed linear series of cells;-D, prothallium taking the form of a leaf-like expansion; a first, and b second radical fibre; c, d, the two lobes, and e the indentation between them; f,f, first formed part of the prothallium; g, external coat of the original spore; h, h, antheridia.

rounding off of its angles; this is followed by the putting forth of a tubular prolongation (B, a) of the internal cell-wall, through an aperture in the outer spore-coat; and by the absorption of moisture through this root-fibre, the inner cell is so distended, that it bursts the external unyielding integument, and soon begins to elongate itself in a direction opposite to that of the root-fibre. A production of new cells by subdivision then takes place from its growing extremity; this at first proceeds in a single series, so as to form a kind of confervoid filament (c); but the multiplication of cells by subdivision soon takes place transversely as well as longitudinally, so that a flattened leaf-like expansion (D) is produced, so closely resembling that of a young Marchantia as to be readily mistaken for it. This expansion, which is termed the prothallium, varies in its configuration in different species;

but its essential structure always remains the same. From its under surface are developed, not merely the root-fibres (a, b) which serve to fix it in the soil, and at the same time to supply it with moisture, but also the antheridia and archegonia, which constitute the true representatives of the essential parts of the flower of higher Plants. Some of the antheridia may be distinguished at an early period of the development of the prothallium (h, h); and at the time of its complete evolution these bodies are seen in considerable numbers, especially about the origins of the root-fibres. Each has its origin in a peculiar protrusion that takes place from one of the cells of the prothallium (Fig. 146, A, a);

Development of the Antheridia and Antherozoids of Pteris serrulata :-A, projection of one of the cells of the prothallium, showing the antheridial cell, b, with its sperm cells, e, within the cavity of the original cell, a;-B, antheridium completely developed; a, wall of antheridial cell; e, sperm cells, each enclosing an antherozoid ;-c, one of the antherozoids more highly magnified, showing a, its large extremity, b, its small extremity, d, d, its cilia.

this is at first entirely filled with chlorophyll-granules; but soon a peculiar free cell (b) is seen in its interior, filled with mucilage and colorless granules. This cell gradually becomes filled with another brood of young cells (e), and increases considerably in its dimensions, so as to fill the projection which encloses it; this part of the original cavity is now cut off from that of the cell of which it was an offshoot, and the antheridium henceforth ranks as a distinct and independent organ. Each of the secondary cells (B) contained within its primary cell, is seen, as it approaches maturity, to contain a spirally coiled filament; and when they have been set free by the bursting of the antheridium, they themselves burst and give exit to their "antherozoids" (c), which execute rapid movements of rotation on their axes, partly dependent on the six long cilia with which they are furnished. The archegonia are fewer in number, and are found upon a different part of the prothallium. Each of them at its origin presents itself only as a slight elevation of the cellular layer of the prothallium, within which is a large intercellular space containing a peculiar cell (the "germ-cell"), and opening externally by an orifice at the summit of the projection; but when fully developed (Fig. 147), it is composed of from ten to twelve cells built up in layers of four cells each, one upon another, so as to form a kind of chimney or shaft, having a central passage that leads down to the cavity at its base, wherein the germ-cell is contained. Into this cavity the antherozoids penetrate, so as to come into contact with