LATI.
Tilts order is easily distinguished from the foliose or operculate musci, by the want of an operculurn, and by that part of the calyptra which is separated by the elon gation of the frnitstalk, or growth ol the capsule, falling immediately. In some instances, the calyptra merely splits, without the separatiun of any part, to allow the capsule to escape.
The natural character of this order may be stated thus: Flowers clicecious or moncecious, destitute of succu lent jointed threads, usually on a proper receptacle, but in the genus Alarchantia, on a common one. In situa tion they are radical, axillary, or terminal; they very rarely originate from the underside of a frondose stem.
Male flowers.
Calyx, none; except, perhaps, in the genus Antho ceros, in which the cup-shaped receptacles may be term ed calyces.
Stamens. Anthers in general spherical or ovate, but varying in form in different genera, and even species ; imbedded in a common peltate or wartlike receptacle ; in the substance of the frond ; sessile, or on short fila ments on the upper or lower side of the frond ; or on filaments, in general more elongated, and situated, in general, several togLther within the same leaf, but some times solitary ; the leaves in the axils of which they oc cur, are in general closely imbricated, but sometimes patent.
Female flowers.
Calyx rarely absent, monophyllous, containing several pistilla, rarely a single pistillum.
Calyptra bell-shaped ; attached to the receptacle ; free around the germen ; forming the outer covering of the style, and a considerable part of the stigma.
Pistilla various in form ; germen ovate ; sometimes obovate ; rarely spherical ; style filiform ; stigma in ge neral somewhat widened.
Pericarp, unknown in Sphxrocarpus ; in the others a capsule, valvular, or at least toothed, except in Riccia; generally situated on a fruitstalk, sometimes sessile or immersed ; containing numerous seeds, intermingled, in most instances, with elastic filaments, which arc usually spiral.
Seeds, in general spherical or ovate, smooth and brownish ; but they vary considerably in form, surface, and colour.
Minute plants, of annual, biennial, or perennial dura tion, the greater number of the species of the order leafy, and all these species belong to one genus; some other species of the same genus, and all the species of the other genera, are frondose. They grow erect, or less or morc inclined, or they creep along the ground. They always prefer moist situations ; and, in some few instances, grow in water.
Anatomy and Physiology of 111usei Hepatici.
Like the foliose mosses, the Hepatic consist entire') of cellular tissue.
Except in the section of frondose species, in which the texture is comparatively dense, the cellular tissue of the Jungermannix is much more lax and delicate than that of the foliose musci. Hence many of the species will
wither almost as soon as they are gathered, if they arc not immediately put into a vasculum, or laid out in paper.
In this genus, the cellular tissue contains a clear Iluid, with particles of different colours in different parts of the same spccies, and sometimes varying in different va rieties of the species, swimming in it. In the stems, when the plants are in health, these particles arc usually of an olive-green or purple colour. In the leaves, they vary in colour in different species, being brown in J. junipetina, purple in some varieties of J. nemorosa, J. compressa, All the species of the other genera are invariably frondose.
The species of Alarchantia are of a dense firm tex ture, somewhat carnose, evidently reticulated, the pre vailing colour of the upper surface a bright green, with a light coloured prominent spot in each reticulation ; the under surface is covered with a membrane, frequently rugose, in which the green is less vivid, or it sometimes is of a reddish colour. In AI. hemisphxrica, the under surface is of a dark purple.
In structure, the genus Targionia approaches nearest to Marchantia, of which indeed it has completely the habit ; the same dense texture, the bright green upper surface, with numerous light-coloured prominent spots of the frond. The under surface is quite black ; in some instances it would appear that it is covered with reddish membranes.
In Riccia glauca, the best known, and indeed the only certain British species of this genus, the form and size of the cells is remarkably regular, being nearly oval, and all nearly of the sante size, except towards the edges. It is of a thick carnose consistency, and is roughened with prominent points on the surface, thus evincing some affinity to Alarchantia, though it differs remarkably in several other particulars, to be afterwards mentioned.
In Sphmrocarpus, the texture is considerably different, being much more delicate and membranous. Its cellular structure is sufficiently obvious under the microscope, and the cells, though often hexagonal, or pentagonal, ap pear to vary remarkably in form.
In delicate membranous habit, Anthoceros approaches somewhat near to Sphzerocarpus; and when sterile, it bas considerable resemblance to minute fronds of Jun germannia epiphylla. Its reticulations, as seen under the microscope, are pretty regularly hexagonal ; and in Anthoceros lxvis have, like Marchantia and Riccia, a prominent spot in the centre.
In Monoclea, the external appearance of the frond is considerably like that of Jungermannia epiphylla ; but the texture is much more dense and coriaceous, and the reticulations are indistinct.