IX. MUSCI. 925 



The cells of the tissue of the leaves form regular dodecahedrons, or a dense 

 parenchyma (Mnium, Orthotrichum, &c.), or elongated dodecahedrons, or rhomboids 

 (Bryum), or approach vermicular fibrous cells (Hypnum, &c.); in Diclielyma, and in 

 the midrib and marginal edge of many other species, the cells lengthen so much as to 

 resemble vessels. The cells often vary in form and size in the same leaf, being 

 usually larger and more elongated towards the base of the blade than towards the 

 top, and formed of a thinner membrane, and deprived of chlorophyll ; the marginal 

 series is always composed of narrow cells which often project under the form of 

 tubercles or teeth (Polytrichum, &c.), or branched hairs (Buxbaumia, &c.). The cell- 

 membrane itself is smooth or covered with papillae, whence the name of papillose 

 cells (Barbula). In certain Mosses the foliar parenchyma is composed of several 

 similar or dissimilar cellular layers (Leucobryum); in the latter, each layer is homo- 

 geneous ; in some the cells are small, elongated, nearly cylindric, full of chlorophyll ; 

 in others they are large, nearly octahedrons and tubular, with hyaline walls pierced 

 with holes, and deprived of green granules. These layers are alternate, and the 

 tabular cells always cover both surfaces of the leaves. 



REPRODUCTIVE ORGANS. Mosses are 2-sexual ; both sexes may occur in the 

 same involucre, or in separate ones, and the plant is accordingly monoecious or 

 dioecious. In the 2-sexual Mosses the two reproductive organs are intermixed in 

 the centre of the involucre, or arranged in two groups, or contained in separate 

 special involucral leaves. The inflorescence dinners in external appearance in the 

 two sexes ; the involucre of the male flowers is termed a perigonium, that of the 

 female a perigynium, and that of the 2-sexual perigamium. The two latter form an. 

 elongated, nearly closed bud, composed of leaves resembling the cauline leaves, of 

 which, in fact, they are a modification ; the perigonium is stouter, and its leaves are 

 larger and more concave. At the time of the development of the fruit, a new cycle 

 of leaves, which are in a rudimentary state before fertilization, is simultaneously 

 evolved ; it bears the name of perichcetium, and varies in form in different species. 



The paraphyses are jointed filaments found in the inflorescence of most Mosses : 

 in the ? they are simple filiform bodies, composed of a single series of cells ; in the 

 $ filiform, clavate or spathulate, and terminated by several series of cells. 



The perigonium is often traversed by the stem, which is sometimes continuous 

 (Polytrichum) through several superimposed series of perigonia, a character peculirv.* 

 to Polytrichum, as is also the presence of an epiphragm, closing the urn. 



The ANTHERIDIA, or male organs, are little elongated cylindric or sub-spherical 

 (Buxbaumia) usually very shortly pedicelled sacs formed of tabular cellular tissue 

 filled with green granules, enveloped in an extra-cellular thick and hyaline sub- 

 stance, and filled with a granular mucilage, destined to be expelled by jets 

 through an apical opening in the antheridiurn when the latter is mature. The 

 mucilaginous mass filling the antheridium is composed of spherical hyaline cells 

 00026 to -00039 in. in diameter, each containing a filiform antherozoid, and 

 furnished anteriorly with two extremely slender vibrating hairs, which equal it in 

 length. The antherozoid describes a spiral of two turns within the mother-cell, and 

 presents, either in the middle, or at the posterior part, a heap of 12-20 amylaceous 



