864: MOSSES organs, and seed-like bodies or spores which serve to propagate the species. They are cel- lular, and bear only a faint resemblance to the higher orders of plants. The stem of the mosses consists of cells of different forms and sizes, as may be readily seen by a transverse section, where those of the circumference are smaller and polyhedral, while those of the centre are elongated and by a closer arrange- ment approximate a woody texture. The stem, when it rises upward and ends in the organs of reproduction, is said to be determinate, and such a moss is acrocarpous ; but when it ex- tends lengthwise and laterally in an indefinite manner, it is said to be indeterminate, and the moss is pleurocarpous, because the reproduc- tive organs are borne upon the side branches. The leaves of mosses are always sessile, and usually clothe the stem; but in some species the lower part is bare, or at least only cov- ered with a few leaf-like scales. There are two distinct kinds of leaves: 1, those which grow upon the stem, and are called cauline ; 2, those which surround the reproductive organs, and are called perichfetial when they surround the fertile organs, and perigonial when around the male. These latter are more closely set than are the others, forming a sort of rosette in the centre of which the reproductive organs are lodged. The leaves of mosses are very simple, and usually consist of a single cellular layer, and they are destitute of stomata. They easily imbibe moisture, and as suddenly wither. A passing shower will revive the mosses which grow upon the driest rocks. The cells of the leaves are comparatively large, but the size differs greatly in different species. Each cell usually contains chlorophyl, though the cells of the sphagnum appear to be destitute of this principle. The cells are often uniform in size and general shape, except those toward the central portion of the leaf, where they assume an elongated form and constitute themselves into a sort of rib, nerve, or vein, which either bifurcates at the base and shortly ceases, or is produced into a single nerve and continues through the greater length of the leaf, or even extends beyond the apex and ends in a sort of point. The cells upon the edges of the leaf are sometimes modified into a border or into serrated processes like teeth. Sometimes sev- eral laminsB are produced along the midrib or nerve of the leaf, and sometimes granules or bulbules are produced there. Buds or innova- tions are also sometimes to be met with in the axils, which when separated can become new plants. With regard to the stem, the phyllo- taxis or position of the leaves is one-two, two- five, or three-eight. The floral or reproduc- tive organs are of two kinds: 1. What may be regarded as the sterile or male flowers, the antheridia, consisting of cylindrical, pear- shaped, or ellipsoidal stalked sacs containing a granular mucilage, which when the antheri- dium is mature is expelled from an opening in the apex ; it consists of spherical hyaline cells from j^Va- to TTnre of an i nc ^ i n diameter, each containing a filiform antherozoid, which is fur- nished with two minutely slender, vibrating hairs. The antheridia are accompanied by Sterile Inflorescence. 1. A sterile Stem. 2. Antheridia (one emitting antherozoids) and Paraphyses. 8. An- therozoids. cellular jointed filaments called paraphyses. 2. The archegonia, which may be compared to fertile or pistillate flowers, are usually flask- shaped bodies, mixed, like the antheridia, with paraphyses, and like them produced within small clusters or rosettes of leaves. The cavity of the archegoniuin contains a free cell or nucleus, enveloped by mucilage; after fertili- Fertile Inflorescence. 1. A fertile Stem. 2. Capsule with its Calyptra. 8. Capsule deprived of Calyptra. showing the Operculum. 4. The same with Operculum removed, exposing the Peristomium and Epiphragm. zation the archegonium elongates, as does its enclosed nucleus ; but the nucleus grows much more rapidly than the archegonium, which at length is ruptured, its upper part forming a
