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 LICHENS LICHFIELD 411 nivalis the Icelanders make soup and even bread. According to Olafsen, one ton of Ice- land moss is equal to half a ton of meal. (See ICELAND Moss.) Lecanora esculenfa, of the steppes of Asia, is eaten by the nomadic tribes of those regions. This occurs in masses about the size of a filbert, and so like the stones in appearance that it needs a practised eye to de- tect it ; as it has never been found attached to any object, it is regarded as having fallen from heaven, like the manna of the Israelites. The tripe de roche (umbilicaria Muhletibergii), mixed with the roe of fishes, assists in making nutritious food for the North American In- dians. Sir John Franklin was indebted to this lichen for subsistence after a four days' absti- nence when on his journey to the shores of the polar sea. Lichens afford valuable mate- rials for dyeing, of which the parelle (Lecanora parella) and cudbear (L. tartarea) may be cited as familiar instances. To these may be added urceolaria scruposa and cinerea, with parmelia saxatilis, omphalodes, conspersa, &c. Rocella tinctoria, fuciformis, intricata, &c., inhabitants of the shores of the Mediterranean or of the coast of Africa, Chili, &c., yield ar- chil. Even the common yellow wall lichen (parmelia parietind), so abundant near our sea- coasts, possesses a peculiar principle called pa- rietine (Thompson), which forms a bright yel- low coloring matter; this is heightened by nitric, sulphuric, or muriatic acid, and alkalies change it to a rich purplish red. The chemical constituents of lichens are phosphate of lime, salt, manganese, iron; several principles, as picrolichine, variolarine, orceine, cetrarine, inu- line, erythrine, rocelline, picroerythrine ; sev- eral acids, as parellic, usnic, orceic, and ery- thrynic acid, and others; uncrystallizable su- gar, oil, waxy matter, resinous matter ; crystals, and oxalate of lime in the tissues especially of lecanora tartarea. The name lichen was ori- ginally given by the ancient naturalists to cer- tain species, because of a fancied resemblance to the cutaneous disease so called, whence they were supposed to be specifics for it. The works of Acharius, though published early in the present century, are still employed by students in lichenology ; his Lichenographia Universal (Gottingen, 1810) and Synopsis Methodica Lichenum (Lund, 1814) are useful works of reference. Among other important European works upon the subject are Fries's Lichenographia Europaa reformata (Lund, 1831); Nylander's Synopsis Methodica Liche- num (Paris, 1858) ; and Tulasne's Memoire sur les lichens (Paris, 1852). Berkeley's "Intro- duction to Cryptogamic Botany " (London, 1857) treats of the structure in this and the related families. The first enumeration of American lichens is to be found in Gronovius's Flora Virgirtica (1761); Muhlenberg's Cata- logue Plantarum (Lancaster, Pa., 1813) enu- merates 184 species; and several other works record American lichens. Halsey's "Synop- tical View of the Lichens of New York " ap- peared in the "Annals of the New York Ly- ceum of Natural History," 1823. Various pa- pers upon lichens by Profs. Edward Tucker- man and J. Lewis Russell are to be found in the " Boston Journal of Natural History " (1838 et seq.). Prof. Tuckerman, now of Amherst college, who has devoted himself more thor- oughly than any other American botanist to these obscure plants, besides the memoirs above referred to and others in Silliman's " Journal of Science and Arts " (1858-'9), has published an " Enumeration of North American Lichens" (Cambridge, 1845), and a "Synopsis of the Lichens of New England and of the North- ern States and British America " (Cambridge, 1848). The same author's Lichenes America* Septentrionalis Exsiccati (1848-'51) consists of six fascicles of specimens, and is an important contribution to American lichenology. In an enumeration of this author's labors we should not omit a memoir in Agassiz's "Lake Supe- rior " (Boston, 1850), and one in the "Botany of Wilkes's Exploring Expedition," recently published. Since the publication of Prof. Tuck- erman's earlier works much progress has been made in the study, and his promised work on the "Genera of North American Lichens" will no doubt embody whatever is now known of these obscure forms of vegetable life. LICHFIELD, an episcopal city and municipal and parliamentary borough of Staffordshire, England, and a county in itself, situated on a small branch of the Trent, and on the London and Northwestern railway, 110m. N. W. of Lon- don ; pop. in 1871, 7,380. It is well paved and lighted, and amply supplied with water, and the principal streets are lined with handsome and well built houses. The most interesting public edifice is the cathedral, parts of which display the early English architecture. It is 410 ft. long, 153 ft. wide across the transepts, and has three spires, the central one of which is 280 ft. high. It was founded in the 7th century, but the present building dates from the 12th and 13th centuries. It occupies an elevated site, and is visible from a great distance. Its interior cor- responds with the exterior in the magnificence of its architectural decorations. Among its numerous monuments are those of Dr. Sam- uel Johnson, Garrick, and Lady Mary Wortley Montagu, and Chantrey's celebrated group of the sleeping infants. The cathedral suffered much during the siege of the town by the parliamentary forces in 1643, but has since been twice thoroughly repaired. Other no- table churches are St. Chad's, St. Mary's, and St. Michael's, the first of which is the most ancient in the city. There are also several national schools, a grammar school founded by Edward VI., a savings bank, a theatre, and a guildhall. On the W. side of the market place is the house in which Dr. Johnson was born, and in the same street is his statue in a sitting posture, 19 ft. high, on a pedestal ornamented with bass-reliefs illustrative of his life. The chief manufactures are paper,