distinctly roughened or granulated as in Hypnum rutabulum. It may be straight or variously curved.
The base of the fruit-stalk is surrounded by leaves which in some species differ remarkably in both form and structure from the other leaves of the plant. These are the perichætial leaves, and the character of these leaves often forms s special feature in the description of mosses. If these leaves are carefully removed it will be seen that the base of the fruit-stalk is surrounded by a membranous sheath, the vaginula, (10 c,) already mentioned; this is usually smooth, but in some species it is more or less clothed with hair-like processes, and these minute differences are in some cases great aids in the discrimination of nearly allied masses.
At the top of the fruit-stalk is the capsule or urn, (1 c, 5 b,) and this organ presents great variety in its form, in some cases globose, Phascum caspidatum; pear shaped, Leptobryum pyriforum; cylindrical, Tortula aloides straight, curved, or erect, Tetraphis pellucida, (12;) cernuous (curved to one side) as in Hypnumrutabulum, (5,) or pendulous as in many of the Bryums; it may be smooth, striated, or furrowed.
In some species the capsule, (14 b,) is swollen all round at the base (14 c,) and this swollen part is called the apophysis, as in Splachnum sphæricum; this apophysis may be seen at the base of the capsules of Polytrichum commune, but not so exaggerated as in Splachnum, sometimes the swelling is confined to a little bulging out of one side of the base of the capsule as in Dicranum falcatum, (13 b) or in Dicraneila cerviculata or Ceratodon purparcus, &c.; the capsule is then said to be strumose.
The capsule is surmounted by a membranous hood called the calyptca, already mentioned as being developed from the upper portion of the fertilised archegonium, (10a, 17, 18.) In some genera, such as the Biyums, this hood falls away early, and hence is not seen upon the mature capsule, but in many other genera, such as Tertula, Hypnum, &c., it is persistent and may readily be seen. In the act of separation from the lower part of the archegonium, or vaginula, the calyptra is sometimes irregularly torn at its base as in Grimmia apocarpa, or it may be evenly torn as in Eucalypta vulgaris. In both eases the calyptra is termed mitriform er mitre-shaped {10 a.) In many other mosses it is slit up one side, and is then said to be dimidiate, (Lat., dimidium, a half) (18,) or it may be inflated as in Funaria, (17,) and these characters are constant. Usually the outer surface is smooth, but in some species it is papillose, and in others more or less densely clothed with hairs as in Orthotrichum and Polytrichum.
The month of the capsule is closed with a little lid called the opeculurm, (12 a, 13 a, 14 a), and between the lid and the mouth of the capsule a ring of minute, highly hygroscopic cells frequently occurs called the annulus, (Lat., a ring.) The function of this ring is that of casting off the lid when the spores are ripened, and thus aiding their dispersion, but in many mosses, such as Tortula ungalaculata, there is no annulus, and the lid is then cast off by the swelling of the contents of the capsule. The operculum is not always present, and here nature adopts other means to bring about the dispersion of the spares; in the Andreæas or split-mosses, (19,) the capsule splits into four valves, (19 a.) and in the Phascums or
