These sections and subsections exhaust the leafy spe cies. The Frondose species ale divided primarily, into, (1) such as arc nerveless, as J. pinguis, J. multifida, (2) such as are furnished with a nerve ; and this section is subdivided according as (a) the calyx is single, for in stance, in J. Blasia, J. cpiphylla, (b) the calyx is double, as in J. Lyellii,J. hibernica.
The neighbourhood of Edinburgh abounds in Junger mannix ; J. Blasia has been gathered in fruit in Peebles shire, in the autumn of 1818 and 1819 ; and some very rare and curious species, as J. setiformis, J. Doniana, J. albescens, have been discovered in Britain, hitherto only on the Scottish Alps.
II. Monoclea. No common receptacle of the fruit, Capsule univalve, opening longitudinally on one side ; seated on a fruitstalk longer than the calyx.
Of this interesting genus, only one species, M. Forsteri, is known, which was gathered in some one of the South Sea Islands, by Mr. G. Forster. It differs from Antho ceros. to which genus Mr. Forster had reduced it, in possessing true spiral filaments, in the want of a colu mella and of a calyx, as well as in being univalve.
III. Marchantia. Receptacle of the male flowers pel tate or wart-like, with numerous antherx embedded in its disc. Female flowers. Common receptacle peltate, flow ming beneath. Capsules opening at the summit by revolute valves.
Of this genus only eight species appear to be known, all of which, but one, were enumerated by Lini.xus; and no fewer than five of them are indigenous to Britain. Of these, AI. cruciata, hemisplixrica, and M. androgyna, are rare. AI. polymorpha is extrt.mely common, and is one of the plagues of gardeners, oyer running their flower-pots and beds. AI. conica is plenti ful by the sides of streams; but rather capricious in pro ducing its fruit, which, when it occurs, is usually mature in Alarch or April.
IV. Anthoceros. Alale flowers, scattered, wartlike.
Female. Calyx tubular. Capsule subulate. Secds numerous, rough, attached to the valves, as well as to the columella.
Of this genus, three species, A. punctatus, A. laevis, (or major,) and A. multifidus, are known; of which the two former are indigenous to Britain. They grow in clover and turnip lields, and produce fruit in winter.
V. Targionia. Capsule globose, of two concave valves. Seeds numerous, combined by fibres into a globe.
Only one species is known, T. hypophylla ; which was first found in Italy, and figured and described by Michell. 'Within these few years it has been ascertained to be a British species. It grows on the sides of dripping rocks, producing fruit in spring.
VI. Sphxrocarpus. Calyx monophyllous, inflated, entire. Seeds very numerous, collected into a globe, in the bottom ol the calyx.
Contains only one species, Spit. terrestris; which grows in the same places, and at the same time, with Riccia glauca—though it is apt to be mistaken, on a cursory view, for a Phascum. Its glaucous hue distinguishes it, at first glance, to those who have once seen it.
VII. Riccia. iNIale flowers, scattered, wartlike.
Female, germen globose, embedded, with the lower part of the style in the frond. Capsule exposed, globose, crowned with the style. Seeds numerous, elliptical.
Of this genus, five species are usually enumerated ; of which three, R. glauca, R. natans, and R. fluitans, are British. R. natans and R. fluitans, uncertain species, as their fruit is unknown, are rare, and occur among duck weed, Etc. floating on the surface of stagnant pools. R. glauca is very abundant in croft lands and clover fields, in the beginning of winter.
Excluding the genus Jungermannia, which has heen already so well illustrated by Dr.,Hooker, there is, within the ample bounds of systematic botany, perhaps no tribe of plants more inviting, as the subject of a short mono graph, than the hepatic mosses. In regard to them, the best treatises, hitherto published, not unfrequently give statements directly opposite, and in general without the slightest intimation that a difference of opinion exists on thc points in question. Several of these discrepancies, the monographist, having the plant before him, with the proper instruments, might remove for ever without much difficulty. Some of the species are indeed not easily ob tained ; but this surely need be no impediment to thc un dertaking, considering the liberality with which all who are known in botany, in the present age, communicate specimens, and elucidations, whenever they see reason to believe that it may be for the advancement of the sci ence ; and even, in very many instances, for the mere gratification of an amatcur.