62. Changes preparatory to the development of the spores.— An axile cylindrical column, consisting of four cellular piles, becomes dis tinguished from those surrounding it by the cessation of the division of its cells by hori zontal septa. In the layer which immediately surrounds it, on the contrary, division by hori zontal septa occurs twice as frequently as in any other portion of the fruit. The hitherto homogeneous parenchyma becomes in con oblique septum, which is followed by a number of others, alternately inclined in opposite directions. This results in ,an egg-shaped body, perfectly separable from the surround ing tissues. The last-formed summit-cell now divides by a septum which is inclined not in the opposite direction, but in a direction at right angles to that of its predecessor. This is followed by a second in the same relation ; that by a third, and so on continuously. The cylindrical rudiment now consists of four columns of cells, each of which is divided symmetrically by a vertical septum, into an external trapezoid and an internal three-sided cell. The former again divides, first, by a ver tical, then by a horizontal septum, both of them perpendicular to the surface of the rudi Ment, which now consists of four central cel lular columns, which are enclosed in eight others formed of trapezoidal cells. These last divide by vertical septa, alternately paral lel and perpendicular to the external surface, by means of which the rudiment gradually thickens. This process goes on much more actively at the lower than at the upper or middle portion, in consequence of which it becomes club-shaped ; its swollen base being sequence distinguishable into three portions — an external, of about five concentric layers of trapezoidal cells (the future capsule), an axile portion of elongated columnar cells (the future columella), and, interposed be tween these, a single layer of tabular cells, whose greater surfaces are horizontal (the cells from which are formed the spores and elaters).
63. Development ofthe spores.—Those of the cells last mentioned, which are destined to become the mother-cells of spores, soon be come detached from their neighbours, and assume a spherical form. Each at first con tains a large central nucleolated nucleus, and a quantity of granular mucus. Soon this last arranges itself in two masses, at opposite sides of the central nucleus. Each of these masses is transformed into a new nucleus, from which radiating threads of mucus stretch to the internal surface of the corresponding half of the cell. Each new nucleus is, when fully formed, vesicular, possessing a membrane of extreme delicacy, and is surrounded by a layer of protoplasma. At a later period its contour becomes cloudy and indistinct ; this change being preparatory to a second division, which results in the formation of four new nuclei similar to the first two; these soon place themselves in such a manner, that each would occupy one angle of a regular tetrahedron contained in the parent cell. Up to this point the original central nucleus has remained ; it now disappears, and six septa are formed simultaneously, which radiate from the centre to the circumference, one between every two nuclei, in such a manner as to divide the parent cell into four compartments, which are the special parent cells of the spores.
In each new cell, after this wall has become thickened by the deposition of a gelatinous material on its inner surface, a spore is formed, which, even at the first appearance of its membrane, occupies the whole cavity. As it approaches maturity, it assumes a brownish yellow colour, its external surface remaining perfectly smooth. In those of the cells of the middle layer of the half-ripe fruit, which are destined to the formation of the so-called elaters, the tubular form is permanent. In each cell the nucleus disappears, and is re placed by two others, between which a per pendicular septurn is formed. From a repeti tion of the same process, there results a cylindrical body consisting of a series of four cells, the fully formed elater.
64. No sooner are the spores of the upper part of the capsule ripe, than it splits into two valves ; dehiscence commences at the apex, leaving, as it proceeds, the columella with the loosely attached spores and elaters.
65. Jungermannifx frondosw.—From Antho ceros we pass to a group of plants, which, while they resemble it in their mode of growth, differ from it considerably in the form of their antheridia and archegonia, and still more in that of the organs in which they are contained. Here as in Anthoceros we follow the descrip tion of Hofmeister (Pellia epiphylla).* 66. First period.—Germination of the spores. —The spore is an ovoid cell, divided into four by three transverse septa, and enclosed in a finely granular external membrane. Of the four cavities, one of the terminal ones dis tinguishes itself from the rest by the small quantity of chorophylle which it contains. This cavity, or rather the cell which it represents, develops in germination, to the first hair-like roots ; while the others, by successive divisions by septa in the direction of the long axis of the spore, form the rudi mentary flattened stem of the young plant.
67. The antheridia.— The rudiments of the antheridia make their appearance as club shaped projections of the upper surface of the young spring shoots. Each such projec tion originates from a single cell of the super ficial lay er by a mode of division which cor responds in every respect with that described in Anthoceros (§59). The completely formed antheridium consists of a globular mass of very small four-sided tessellar. cells, which is surrounded by an outer layer of about twenty flattened cells, containing chlorophylle granules in contact with each other by their marg,ins ; the whole is supported on a very short stalk, consisting of only four cells. Each of the small cells contains a lentil-shaped vesicle, within which a spiral fibre is rolled up. This fibre moves with great activity for about ten minutes after its escape, revolving round its own axis, and at the same time progressing rapidly. The posterior extremity is slightly thickened, while from the anterior which tapers off gradually to a point, there ema nate two long and delicate cilia, like those of the antherozoids of Chara. These, as well as the slender prolongation of the tail, mani fest an active " winding screw-like" motion. These phenomena remain in perfection only for about ten minutes after the escape of the filament.