Liverwort, or Lichen, L. a genus of perennial plants, comprising 363 species, the greater number of which are natives of Britain ; - the most remarkable of these are:

1. The calcareus, Calcareous, or Black-nobbed Dyers' Liverwort, which grows on lime-stone rocks in the North of England and Wales, and is in flower from July to December.—This species is so peculiar to lime-stone rocks, that, wherever these are found among other soils, they may immediately be distinguished by the appearance of this plant.—When dried, pulverized, and steeped in urine, the calcareous liverwort is employed by the Welsh, and by the inhabitants of the Orkney Islands, for dyeing a brilliant scarlet colour. It should be gathered in August, completely dried, then reduced to powder, and steeped in urine for three weeks, in a close vessel.

2. The parellus, or Craw-fish-eye Lichen: it grows on rocks, walls, stones, and on the trunks of trees ; flowers from January to December..—This vegetable abounds on the rocks in the North of England, where it is collected, and sent to London in casks. It imparts a red colour, and is used in making the blue pigment, known under the name of litmus.

3. The tar tartareus, or Large Yel-low-saucered Dyers' Liverwort, which abounds in the Highlands of Scotland, and in the county of Derby : it incrusts most of the stones at Urswick-Mere. and is in flower from' January to December.—In Scotland, this species is gathered ; cleaned ; and, after being steeped in urine for the space of three months, it is formed into cakes; which, when dried, are pulverized, and employed for imparting to wool a fine scarlet colour, with the addition of alum: In England, it is collected and sold at the rate of one penny per pound, to dyers, for striking a purple dye.

4. The ompha/odes, or Dark-coloured Dyers' Liverwort, Cork, Corker, or Arcell, which grows on rocks in several parts of Britain, and flowers the whole year. It is prepared in the same manner as the preceding species :- with the addition of lime, and a little salt, it imparts a reddish-brown to woollen cloth; which, if it be afterwards dipped in the blue vat, will acquire a beautiful purple tinge.— The dark-coloured liverwort is an useful styptic: it was formerly reputed in inflammatory levers, cutaneous affections, and disorders of the liver; but is now justly exploded.

5. The vulpinus, or Gold-wiry Lichen, is found on the trunks of old trees, in various parts of Britain, and flowers during the whole year. It communicates a yellow colour to yarn 3 and, when mixed with pulverized glass, is strewed on carcasses in Norway, to destroy the wolves which infest that country.

6. The prunaslri, or Common Ragged Hoary Liverwort, which grows on the trunks and branches of trees, and is in bloom from January to December. This species possesses the remarkable property of imbibing and retaining odours; on which account its leaves, when pulverized, form the basis of several perfumed powders : they also communicate a red colour toyarn,

7. The caperatus, or Wrinkled Liverwort, which abounds on the surface of rocks, stones, trees, and pales ; it also flowers throughout the year. In Ireland, and the northern parts of the Isle of Man, it is employed for dyeing wool of an orange colour. If serge be previously infused, and boiled in urine, or steeped in a solution of green vitriol, and then dyed with this plant, it will assume a fine russet-brown tinge ; but, if it be simply immersed in a decoction of the wrinkled liverwort, the stuff will acquire a lemon shade.

8. The pustulatus, or Spotted Liverwort, which is found on rocks in Wales, and the northern parts of Britain ; it flowers during the whole year. According to Lin-Naeus, a beautiful red colour may be prepared from this species ; and Dr. Withering states, that it may be converted into an excellent black pigment.

9. The calicaris, or Beaked Liverwort, grows sometimes upon trees, but more frequently on rocks, near the sea-coast. It is smooth, glossy, and whitish, producing flat or convex shields, very near the summits of the segments, which are acute and rigid ; and, being often reflected by the growth of the shields, appear under their limbs like a curved beak.—This plant yields a fine red colour; and, in this respect, promises to become a substitute for the famous Lichen Roccella (see Orchal), which is imported from the Canary Islands, and Sometimes sold at the price of 80l. per ton.—Both the present and the preceding species (Lichen pustulatus), were formerly employed instead of starch, in the manufacture of hair-powder.

10. The aphthosus, or Green Ground-Liverwort; it grows on moist rocks, in shady, stony, and mossy places, and, like most of the preceding species, is in flower from January to December.-An infusion of this plant is made in milk, and given by the country people to children affected with the thrush.-A decoction of it, in large doses, operates powerfully both as a pur-gative and as an emetic; it is said to be a good vermifuge.

11. The IsIandicus, or Esculent Iceland Liverwort, abounds not only in the Highlands and Lowlands of Scotland, but is also found in some of the more northern parts of England and Wales-The inhabitants of Iceland boil this beneficial plant in several waters, then dry, and make it into bread. They likewise prepare from it a kind of gruel, which is mixed with milk ; but the first decoction is never used ; as it is strongly purgative. A jelly, or thick mucilage, made of the Iceland Liverwort, is recommended by Haller and Scopoli, as an excellent domestic remedy in consumptions.—In Germany, a very durable brown dye is obtained by first boiling linen yarn, for one hour, in a solution of alum and cream of tartar ; then adding to this liquor the dried Iceland Liverwort, and suffering it to boil for half an hour at the least, when the yarn is again to be immersed for a quarter of an hour or longer, stirring it properly, and afterwards plunging it in a weak, cold solution of copperas or vitriol of iron.- But the Iceland Lichen also imparts a very excellent black to white woollen yarn, by previously, boiling it for one hour in liquor made of the dried plant, and an equal quantity of copperas, in pure water; then removing it from this brown dye, and again boiling it for fifteen minutes in a strong decoction of log-wood : thus the wool assumes a deep black colour, which presents no other shade.

12. The pulmonarins, Lungwort-Liverwort, Hazel Rag, or Hazel Crottles, which abounds on the trunks of old trees, especially those of oaks, and on heaps of stones, in moist shady situations.-It has an astringent, bitter taste; and is used in Siberia as a substitute for hops, though it renders the ale narcotic, and occasions the head-ach.- This plant was formerly much esteemed in consumptive cases.—According to Dr. Rutty, woollen cloth dyed with the lungwort, acquires a durable orange colour.

13. The caninus, or Ash-coloured Ground Liverwort, which grows upon the ground among moss, at the roots of trees in shady woods; and is frequently found on heaths, stony places, and in hedges : it is in flower throughout the year.—. This species has acquired its celebrity by Dr. Mead's assertion, that it is an infallible preventive of the consequences arising from the bite of a mad-dog. He directed half an ounce of the dried and powdered leaves to be mixed with two drams of pulverized black pepper, and divided into four doses: one of these was to be taken by the person bitten, every morning fasting, in half a pint of warm cow's milk, for four successive days; after which he was to make use of the cold bath every morning, for 2 rnontht- It is, however, to be regretted, that the success of this, or of. any other medicine recommended for the same purpose, has but seldom proved effectual.

14. The cocciferus, or Scarlet-bearing Liverwort, which is common on heaths, and flowers from October to April. This species assumes various appearances, ae-cording to its age, situation, and other circumstances affecting its growth. It may, however, be easily distinguished by the fungous tubercles, which are of a beautiful scarlet tinge, and grow on the top of its stalk. These excrescences, when steeped in a solution of potash, are said to impart a fine and durable purple.

15. The plicatus, Officinal Stringy Liverwort, or Tree-moss, which grows on the branches of trees in thick woods, and is in flower from January to December. - It was formerly used as an astringent to prevent haemorrhages, and to cure ruptures.- Linnaeusi observes, that the Laplanders successfully apply the tree-moss to their feet, with a view to relieve the excoriations occasioned by too great exercise. Professor Kalms remarks, that if this vegetable be collected from fir or birch-trees, it communicates a green colour to wool, previously boiled in alum-water.

16. The barbatus, v. articulatits, or Bearded Liverwort, thrives in woods, and on the branches of trees; flowering throughout the year. It grows from half a foot to two feet in length, is of a whitish-green cast, and possesses considerable astringency. - When steeped for some time in water, the whole plant acquires a red-orange colour ; which is employed by the inhabitants of Pennsylvania to impart that tinge to various stuffs.

17. The Roccella. See Orchal.

It is remarkable, that the lichens, or mushrooms, cannot be propagated by seed ; and that, with these fungous productions, there appears to commence a new and intermediate kingdom, partaking both of vegetable and animal nature : so that the generation of fungi seems to be involved in a process of fermentation, which suddenly assumes a vegetable form.

Liverwort. - All the indigenous species of the lichens contain a considerable portion of viscid matter ; which has, by the Earl of Dundonald, been successfully converted into a gum, possessing all the properties of the Senega, at present used by calico-printers. - These vegetables abound chiefly on trees, growing in poor stiff soils : they attain to maturity in three or four years ; so that a crop may be taken from the same tree, every fourth year.

The liverwort is furnished with an external skin, beneath which is found a green resinous substance : the remainder is composed partly of gum, and partly of an animal fibrous matter, that is insoluble both by heat and the action of alkalies. In order to extract the gum from such plants, they are first scalded two or three times in boiling water ; in consequence of which, the rind or skin is separated, together with the greater part of the resinous ingredient. The vegetables, thus prepared, are next put into copper vessels and boiled, in the proportion of lib. to 2 gallons of water, for four or five hours ; half or three quarters of an ounce of soda or pearl-ashes, or half a pint of volatile alkali, being added to every pound. The boiling is continued till the liquor acquires a gummy consistence ; when it is strained through a hair sieve, and the residuum is expressed through hair-cloth bags, by means of presses similar to those used by tallow-melters.

The extract thus obtained, is then suffered to stand for 10 or 12 hours ; after which it is strained, and evaporated in lead or tin vessels, placed over stoves moderately heated by fuel, or by the steam of hot water, till it be of a proper consistence for block-printing. If such gum, however, be intended for making ink, manufacturing paper, or staining and stiffening silks, crapes, gauze, etc. Lord Dundon-ald observes (in his Circular Letter addressed to the Calico Printers of Scotland), that no alkaline salts must be employed for extracting the liverwort ; and the boiling be continued for a longer time, and with a moderate degree of heat : thus, the gummy extract will become nearly colourless ; but, if volatile alkali be used, it will be necessary to substitute iron vessels for those made of copper.

Lord D.'s gum has been found to answer every purpose for which it was designed: as its preparation is not only cheaper, and will produce a considerable saving of money annually sent to Senegal, but will also afford employment to numerous women, children, and others, in collecting, as well as in preparing, the lichens, it promises to be a national benefit.