ICELAND MOSS.

567

is distinctly floccose, in the latter occupying' the lower half of the thallus, in the •former enclosed all round by the cortical layer. Reproductive matter of two kinds:

1, sporules (sporula), lying in membranous tubes (theca) immersed in nuclei of themedullary substance, which burst through the cortical layer, and colour and hardenby exposure to the air in the form of little disks (apothecia), which have received dif-ferent names according to their forms; 2, the separated cellules of the medullary layerof the tissue (Lindley , with some additions).

Properties. —The lichens, at least the foliaceous ones, contain a starchy substance(called feculoid or lichenin), which renders them nutritive, emollient, and demulcent.They also possess a bitter principle (cetrarin), from which they derive tonic properties.Several lichens, by maceration in ammotiiacal solutions, develope brilliant colours,which render them valuable as dyes. The colorific principle of Rocella tinctoria istermed erythrin, while that of Variolaria dealbata is called orcin.

Fig. 71 .

Cetraria islaridica, Ach. L. D. (Lichen islandicus, E.)— Iceland Moss.

Sex. Syst. Cryptogamia, Algae .

(Cetraria, Ph . Lond.; Planta , Ph . Dub. ; Lichen Islandicus, Ph. Ed.)

History. —The medicinal properties of this plant (usually termedLichen islandicus ) were probably first known to the natives of Iceland .According to Borrichius, the Danish apothecaries were acquainted withthem in 1673. In 1683, Hiarne spoke favourably of its effects inhaemoptysis and phthisis (Murray, App. Medicam. v. 508).

Botany. Gf.n. Char. — Thallus foliaceous, cartilagineo-membra-naceous, ascending and spreading, lobed andlaciniated, on each side smooth and naked.Apothecia orbicular, obliquely adnate withthe margin of the thallus, the lower portionbeing free (not united with the thallus); thedisk coloured, plano-concave, with a borderformed of the thallus and indexed {Hooker}.

Sp. Char. — Thallus erect, tufted, olivebrown, paler on one side, laciniated, chan-nelled, and dentato-ciliate, the fertile laciniavery broad. Apothecia brown, appressed,flat, with an elevated border (Hooker).

The apothecia are generally wanting onthe plant of the shops.

Hab. —Dry mountainous districts of thenew and old continents. Although met within considerable abundance in Scotland , it isnever gathered there as an article of com-merce.

^ f hysical Characters.— As met with in commerce, Iceland moss is*°Wnish or greyish white, with white farinaceous spots on it, but^ el y having apothecia. It has little or no odour, and a slightly bitter

Cetraria islandica.a < The apothecia on

the

larger lobes of the thallus.

Its powder (or farina) is whitish grey,n '“'FMMerce. —It is imported in barrels and bags from Hamburgh andl8a len ' JUr gh, an( l i s sa hl to be the produce of Norway and Iceland . In5^®’l20,599 lbs. paid duty; in 1837, 12,845 lbs.; and in 1838, only

Composition. —It has been analyzed by Berzelius [Ann. de Chim.Z~ 77 ) , who obtained the following products from 100 parts :— starchyter (lichenin), 44'6 ; bitter principle (cetrarin), 3'0 ; uncrystallizableJar > 3*6 ; chlorophylle, T6 ; extractive matter, 7‘0 ; gum, 37; hi