Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/83

Rh MOSSES.] MUSCINE.E 71 among &quot;vascular&quot; plants that the vascular bundles which run off from the leaf pass into the stem and there apply themselves to others. The stems are thickly set with leaves. It is but seldom that these stand in two rows on the sides, as in Fissidens, Conotnitrium, and the sterile shoots of Schistostega. The last-named plant is of special interest as possessing two kinds of shoots of totally differ ent appearance. The fertile ones have their leaves placed on all sides of the stem in a spiral manner ; the sterile ones, on the other hand, have leaves placed on two sides, and have the appearance of a fern-leaf. This position, however, only comes to pass through a shifting and twist ing of the stem. Originally, in the bud, the leaves of the sterile stems stand in a spiral line. On examination of the end of the stem it is found that the growing point from which the leaves arise contains, as in the foliose Liverworts, an apical cell of the form of a three-sided pyra mid with a vaulted base. By means of partition walls which are successively parallel to one of the side walls of the apical cell &quot;segments&quot; are cut off; and from each of these proceeds a leaf, as well as a part of the rind of the stem and of the inner tissue. On the direction of the partition walls in the apical cell depends likewise the arrangement of the leaves. The branches do not spring as in most phanerogamous plants from the axil of a leaf, but from the upper surface of the stem below a leaf, and only out of one of its cells, which becomes the apical cell of the branch. In the relation of the ramification to the general struc- FIG. 10. Longitudinal section through the summit of a small male plant of Funaria hygrometrica, with antheridia in various stages of development, a is a young antheridium at its point is a &quot; two-edged &quot; apical cell ; 6, an antheridium, nearly mature ; c, paraphyses, hair-like structures which stand between the antheridia and of which the terminal cells are swollen into a globular form ; d, section of leaves through the mid-rib ; e, section of leaves through the leaf-surface (lamina). Magnilied 300 diameters. (After Sachs.) ture of the moss-plant two leading classes have to be dis tinguished the acrocarpous and pleurocarpous Mosses. In the former the growth of the stalk concludes with the formation of a sporogonium ; for the archegonium, out of which the former springs, proceeds from the apical cell itself. In the pleurocarpous Mosses the sporogonium stands on the tip of a side-branch, and the growth of the principal stem is thus not interfered with by fructification. In many acrocarpous Mosses the stalk dies after fructifica tion, and the Moss is then an annual, as in many Phasca- cess. In those acrocarpous Mosses which are perennial the further development is taken up by a side-branch, and a so-called &quot; innovation &quot; is formed. By the dying away of the principal stem, these innovation -shoots become at a later period independent plants. The roots consist of simple rows of cells, spring ing from the surface of the stem, especially at its base (see p. 72). (2) The sexual organs of the Leaf -mosses, the antheridia and the archegonia, in their mature condition correspond in the main with those of the Liverworts, from which, how ever, they differ somewhat in their development. They oc cur generally in groups at the extremity of a shoot. Such groups containing, as the case may be, either solely anther idia, or solely archegonia, or t -, FIG. 11. Sphagnum aciitifoliwn. A. a mixture 01 tile two, are A male branch partially deprived of its leaves to show the antheridia a. B. An open antheridium, very highly magnified. C. A mature motile sper- matozoid. (After Schimper.) termed &quot;flowers.&quot; An ex ception to this condition of the antheridia is found in Sphagnum (fig. 11, A}. Here the antheridia do not stand in groups on the summit of the male branch, but are arranged along it, so as to stand beneath the leaves on the prolonged axis of the shoot. In the rest of the Mosses, with the excep tion of Polytrichum, the first antheridium (or ar chegonium) of a group proceeds from the apical cell itself ; and thus the growth of the shoot con nected with it is closed. The general character of the male &quot; flowers &quot; is very various, in the form of buds, heads, or disks. They are enveloped by a number of leaves, the &quot; perigonium &quot; (fig. 11). The male plants of dioe cious Mosses are often considerably smaller than the female ones. This is the case with Funaria hygrometrica, and to a remarkable extent with Dicranum undulatum and Leucobryum glaucum. Dioecious Mosses are fre quently sterile on account of the absence of one of the sexes. The female &quot; flowers &quot; (fig. 12) are in the shape of buds, enveloped by a number of leaves, which become smaller towards the inside. The archegonia have in general the same structure as those of Liverworts, but are distinguished by a very much developed stalk, diminishing towards the base in the form of a wedge FIG. 12. Longitudinal section through the female &quot;flower&quot; of Sphagnum squarrosum, which shows four archegonia with long stalks. H, the neck portion ; C, the ven tral portion; St, the stalk ; B, ventral canal- cell ; E, oosphere. The archegonium in the middle has proceeded from the apical cell of the shoot.