38

ELEMENTS OE MATERIA MEDICA.

has the usual odour of sea wceds. It consists, according to Dr. O'Shaughnessy, 1 of VegetaldeJelly 54-5, True Starch 15, Ligncous fibre 18, Gum 4, Sulphate and Muriate of Soda 6-5, Sul-

Fig. 107.

Esculenl Sea Weeds.

a, Rhodomenia palmafa (or Dulse),

b, Rhodomenia ciliata.

c, Laminaria saccliarina.

d, Iridica edulis.c, Alaria esculenta./, UJva laticsima.

phate and Phosphate of Lime 1, Wax, Iron and Loss 1. By boiling in water it yields a liquidwhich gelatinizes on cooling, The deeoclion or jelly forms an agreeable, light, nourishing,article of food for invalids and children. It may be used as a Substitute for farinaeeous sub-stanees. a

Order IL—LICHENES, Juss— THE LICHEN TRIBE.

Lichenacea?, Lind.

Essential Character. — Perennial plants, often spreading ovcr the surface of the earth, orrocks, or trecs, in dry plaees, in the form of a lobed and foliaccous, or hard and crustaccousor leprous substartce, ealled a thallus, crust, orfrond (receptaculum commune). This lhallusis formed of a cortical and medullary layer, of which the former is sirnply ccllular, the latterboth cellular and filamentoas. In the crustaceous species the cortical and medullary layersdiffer ehiefly in texture, and in the former being coloured, in the latter enlourless; but in thefrutieulose or foliaccous species, the medulla is distinctly floccose, in the latter occupyingthe lower half of the lhallus, in the former enelosed all round by the cortical laycr. Repro-ductive matter of two kinds: 1, sporules (sporulcv), lying in membranous tubes (theca) im-mersed in nuclei of the medullary substance, whieh" hurst through the cortical layer, andcolour and harden by exposure to the air in the form of little disks (apothecia), which havereceived different namcs according to their forms ; 2, the separated celiules of the medullarylayer of the tissue (Lindley, with somo additions).

Proper/ties. —The liciiens, at least the foliaceous ones, contain a etarehy substance (ealled fe-culoid or lichenin), which rendcrs them nutritive, emollient, and demulcent. They also pos-sess a bitter prineiple (Cetraria), Crom which thcy derive tonie properties. Several lieheng,by maceration in ammoniacal Solutions, devclope brilliant colours, which render them valu-able as dyes. 3

1, CETEA'RIA ISLAN'DICA, Ach. L. E. D.~ ICELAND MOSS.

Sex. Syst. Cryptogamia, Algee.

(Cetraria, L. E. (U. S.);—Planta, D.)

Histoky. —The medicinal properties of this plant, (usually termed Liehenislandicus) were probably first known to the natives of Iceland. According to

i Travsaciions of the Royal Medico-Botanical Society for 1837, p. 181.

» For further partieulars respectingit', see Drs. Sigismund and Farre'swork On the Ceylon Moss. 1840.

a For further detaila respeciingthe useful qualities ofLichena, see the Memairescourmnis en VJinnte [786,par l'Mcademie des Sciences, Belles-Lettrcs et Jtrts de Lyon, sur l'ütilite des Lichens dans In Medecine et dansles Ärls, par MM. G. F. Hoffman, Amoreux fils, et Willmet.—Lyon, 1787.