The calyptra, when torn from the receptacle, is in some instances toile entire at its base, and not in the least cleft in any part, as in Encalypta vulgaris, in ‘vhich 1110Sti, and in the whole genus, it completely encloses the mature fruit. In other instances it is rnitriform, being smaller than in the Encalyptae, and having an indefinite number of clefts, of uo gleat depth, situated all around the base. In other instances it is dimidiate (cucullate, or hood-shaped, as some tertn it) when it is split from the base on one side, for about two thirds or more of its depth, throughout the whole of that part wnich covers the capsule, excepting that in which the beak of the operculum is situated. NVIlen dimidiate, it is in general situated tnore or less obliquely upon the capsule ; when mitriforrn or campanulate,it is situated straight. In ex terior, it is either quite smooth, as in Polytriebuin un dulatum, the Encalyplae, the Hypna, or at least 'nest of them. Sze. or sparse hairs project uprightly from it, as in the Orthotricha; or it is furnished with a dense covering of hairs, not attached to it, except laterally, which are merely the succulent filaments which had adhered to it when it began to rise, in consequence of a glutinous exudation, as in many Polytricha, and in the genus Dawsonia. The true Calyptra of the hairy Polytricha is very small. In general,the Calyptra falls some time before the separation of the operculum, or lid of the Capsule. But it) Encalypta vulgaris, and ciliata, Tetraphis pellu cida, and some others, it persists till the time when the operculum separates.
The chief purpose of the flower of mosses, as of other plants, is the formation of the fruit.
The fruit of mosses is always capsular, and is alway: furnished with au operculurn or lid, situated at the sum rnit of the capsule. For a considerable time before the maturity of the capsule, the difference in colour of the opercnIum, and the appearance of its margin, show that it is to separate by a horizontal line. Yet in three ge nera, Phascum, Vuitia, and Andraea, it never separates; Phascum and Voitia having no regular mode of open ing, and Anclraea being the only genus of mosses known that has a valvular capsule.
In all olive! musses the operculum separates at the maturity of the fruit, and discloses the mouth of the capsule, which is either quite naked, as in Sphagnum ; covered with a horizontal membrane, as in some Gym riostoma, Leptostomum of Mr, Brown, in Drepano phy Hum, in Lyellia ; surrounded by a plaited conical truncate membrane, as in Diphyscium ; or by a toothed or ciliated process, or by both. Tile teeth are always definite in number, and, except in Dawsonia, the cilia also. The lowest number ot teeth is four, in Tetra phis ; the next eight, doubled, Otoblepharem, Fabro nia and Splachnum ; next i6, which are either entire and equidistant, as in Weissia, Calymperes, Grimmia ; or cleft half way down from the summit, as in Dicranum ; or cleft to the very base, or nearly so, in which case they inay also be described as 32, placed in pairs, as in th dymodon, Trichostomum. We find next in Tortilla 32
fililorm twisted teeth, which are united at the base more or less into a tube. In Tayloria splachnoides are found 52 teeth in pairs, arising within and below the mouth of the capsule, curiously folded inwards when the cap sule is moist, twisting outwards, in a singular manner, with a vermicular motion, on the application of drought or heat. The teeth of all mosses indeed have a certain degree of motion. They all expand on the falling of the operculum, and return to thdl' position across the mouth of the capsule in moist weather. But the teeth of no other known moss have the variety, or rapidity of motion, of Tayloria. In Pclytrychum the number of teeth is in some species 32, in others 64 ; in all they are united at the summit by a horizontal membrane. Of musses with a double peristome, some have the ci lia (as the divisions of the inner peristorne are termecl,) unconnected at the base ; as in Funaria, Zygodon, Orthotrichum ; others have them connected at the base by a membrane ; as in Bartramia, Hookeria, Hypnum, Bryum. Fontinalis has for internal peristorne, a reti culated cone ; and Buxbaumia, a plicate, membranous truncated conc. The mosses having a double peris tornc have invariably 16 teeth, and in general, an equal number of cilia. Some species of Orthottichum are irregulat, in O. anomalum, and O. cupulatum, cilia be ing altogether wanting ; in O. crispum, O. Hutchinsix, and 0..affine, only eight being present. In some spe cies ol pnuni and Bryum, filiform processes occur between the cilia. In Dawsonia alone the cilia are Innumerable, and arise equally from the walls of the capsule, and from the central pillar termed Columella. This moss is quite unfurnished with teeth.
In several species of moss, around the teeth is situated an elastic ring ; the untwisting of which, at the maturity of the capsule, assists materially in the disengagement of the operculum.
The walls of the capsule are double, and frequently, at its maturity, a considerable interval is interposed between them; yet in several species they occur always in such close proximity, as, on a cursory view, to appear but a single wall, The exterior is hard, crustaceous, and densely reticulated ; the interior is much more deli cate. The teeth of the peristome always originate in the outer wall ; the cilia, the horizontal, and the conical mem brane from the inner. The operculum seems also to be originally a mere continuation of the outer wall.