Liverworts, a family of cryptogamous plants, called hepaticce by botanists. The liverworts are humble, often very minute plants, in some genera resembling the lichens and in others the mosses, from both of which they differ in their organs of reproduction. In some genera the vegetative portion of the plant is frondose, consisting of a leaf-like expansion of very loose cellular tissue, which spreads upon the ground and emits rootlets from its under surface; this is variously lobed or forked; in other genera there is a distinct stem, bearing true leaves in two rows, and there is often on the under side of the stem a row of rudimentary stipule-like leaves (amphi-gastria); the leaves are entire, toothed, lobed, or even deeply divided, and the form and markings of these as well as of the amphigas-tria being very constant in each genus and species, they afford characters by which the plants may be distinguished when the fructification is wanting. The reproductive organs are of two kinds, corresponding in their office to the stamens and pistils in the higher orders of plants; these are monoecious or dioecious, are sometimes sunk within the substance of the frond as in Riccia, sometimes above it, or, as in Marchantia, elevated upon a pedicel.
The an-theridia, or male organs, consist of numerous oblong or spherical sacs, which when ripe rupture and liberate their contained cells, which in a short time emit the antherozoids, minute filiform bodies which bear at one extremity two still smaller threads. The pistillate organs, termed pistillidia or archegonia, after receiving the action of the antherozoids, increase in size and form the sporangia or the true fructification; these open usually by four valves to discharge their spores, the true reproductive bodies; the spores are contained in fours in mother cells; their dissemination is often aided by elongated cells, the elaters, which are capable of a spirally twisting movement. The capsule or sporangium is usually surrounded by a tubular organ, the perianth, and this again by an involucre, also tubular, or leaves of a peculiar form. Besides this sexual reproduction, liverworts are often multiplied by bulbils, which are variously shaped cellular bodies, capable of growing and producing a plant; these bulbils are in the marchantias produced in little cups, elegantly fringed on their edges, which are situated upon the upper surface of the fronds; in other genera they are produced in different parts of the plant. - The large family of the liverworts is divided into suborders.
Berkeley, who is an authority in cryptogamic botany, makes three, which he thinks should rank as natural orders: 1, the Ricciacece, which consists of a few chiefly floating frondose plants, which produce rootlets from beneath, and have their organs of fructification sunk in the frond, or sometimes seated on its surface; spores without elaters; 2, Marchantiaceae, frondose terrestrial perennials, with the valvate capsules upon the under side of a target-shaped, stalked disk; spores mixed with elaters; 3, Jungermanni-aceae, mostly leafy plants with solitary fruit which splits into four equal valves; spores mixed with elaters. These divisions are in systematic works subdivided by characters afforded by the fruit, leaves, etc. The liverworts are found in all parts of the world where excessive dryness does not prevail; while some are peculiar to temperate or cold regions, others are found only in tropical ones; two species of Jungermannia have been detected enclosed in amber, the only instances in which plants of this family have been found in the fossil state.
The old herbalists called the frondose marchantias liverworts, and from their lobed appearance saw some resemblance in form to that of the liver; according to the then prevailing view, this indicated that the plants were adapted to cure diseases of the liver, and we find them in the early works recommended for liver complaints under the name of hepatica. Though the generic name hepatica is now attached to a ranunculaceous plant, closely related to anemone, the name hepaticae has been unfortunately (as leading to confusion) retained for the liverworts. Some species of liverworts have a strong and peculiar odor and an acrid taste, but so little is known about their uses that they cannot be regarded as of any importance to man. In some cases Marchantia polymorpha (and perhaps others) is sufficiently troublesome to be regarded as a weed; in the moist climate of England it often annoys the gardener by spreading over the rocks of the fernery to the exclusion of other plants, and in greenhouses everywhere it is a frequent intruder; some seeds are very slow of germination, and the soil of the pan or pot in which they are sown will sometimes become so covered with the fronds of Marchantia that the tiny plants cannot force their way through the mass; or after the plants are fairly up, if not watched this liverwort may increase so rapidly as to choke and destroy them.
Liverworts are to be sought for in moist places, on the faces of damp rocks and on the bark of trees; the margins of springs and the beds of streams which become dry in summer are favorite places for the collector; the plants may be readily kept in a growing state, and their development watched, by placing them in a dish under a bell glass and supplying them with water. - When Linnaeus published his Species Plantarum (1753) only 44 species were known, but the number in 1842 exceeded GOO, and the labors of botanists since that time have led to the discovery of many others. The American liverworts were elaborated for the second edition of Gray's "Manual of Botany" (1856) by the late W. S. Sullivant of Ohio, who gave descriptions of 123 species in 38 genera; this memoir, together with that on mosses by the same author, was also published separately under the title of " The Musci and Hepaticae of the United States east of the Mississippi River," illustrated with elaborate copperplate engravings of the structure in each genus. Mr. C. F. Austin of Closter, N. J., who has given special attention to these plants, published in 1873, under the title Hepaticae Boreali-Americanae, a collection of dried specimens; this consists of 150 species, including several not before described.
Besides these works, the student is referred to Schwagrichen, Histories Muscorum Hepaticarum Prodromes (Leipsic, 1804); Hooker, " British Jungermanniae " (2 vols, fob, London, 1818, a beautifully illustrated work); Schweinitz, Hepmticae America Septentrional is (Raleigh, N. C, 1821); Nees von Esenbeck, Hepaticae Javanicae (Breslau, 1831), and Naturgeschichte der Europaischen Lebermoose (4 vols. 8vo, Berlin and Breslau, 1833-'8); Montagne, Essai d'organographie de lafamille des hepatiques (Paris, 1845); Hepa-ticae, in "Catalogue of Plants of Cincinnati," by Thomas G. Lea (1849), and in "Memoirs of the American Academy," new series (1850); and Berkeley, " Introduction to Cryptogamic Botany" (London, 1857). An elaborate account of the microscopic structure and the development of the hepaticae is to be found in Sachs, Lehrbuch der Botanik (Leipsic, 1873).
Riceia natans. - 1. The Plant. 2. Magnified Section. 3. Ca-lyptra and Spores.
Marchantia polymorpha. - 1. Female Plant. 2. Male Plant with cupule. 3. Elater and Spores.