425 



LICHENS. 



LICHENS. 



is imperfectly cellular, without any trace of vascularity. The cells 

 of which they consist are spheroidal or cylindrical, tubular or fibrous, 

 empty or filled with a grumous matter, in a loose and indefinite state 

 of aggregation, but generally consolidated into two strata, the one 

 external or cortical, the other internal or medullary. The membran- 

 ous or other expansion, which in these plants consists of a combina- 

 tion of stem and leaf, is of the most unequal and uncertain degree of 

 development, in Home species appearing like misshapen leaves spreading 

 over the surface on which it grows, in other cases rising up as a stem 

 of various i figures ; but always more or less unsymmetrical, and in 

 many instances constituting little more than a stain upon the face of 

 a tree or rock ; this body is a frond, or, as it is technically called, a 

 Thallus. The fructification of Lichens consists of a round or linear, 

 convex or concave cup, called Apothecium, or Shield, at first closed, 

 but afterwards expanding and producing a nucleus (stratum proligerum) 

 in which are embodied the spores. The shield is surrounded by a 

 border (excipulus) which originates either from the substance of the 

 thallus (thallodes) or from the base of the shield itself (proprius), or 

 from both (thallodes and proprius). 



The prevalent principles found in Lichens are a peculiar kind of 

 starch called Lichenin [LlCHENlN], a bitter secretion, and a resin 

 combined with an unctuous colouring matter, yielding purple, yellow, 

 and brown dyes. In consequence of their bitterness some have been 

 employed as febrifuges, as Variolaria faginea, Parmelia parietina, 

 and several others. 



The following cut shows the various stages of development in the 

 Lichens of this country. 



Lichens in fructification, in various stages of development. 

 l f J'inra barbata, with a stem and rudimentary leaves; 2, 3, Clftdonia pyzi. 

 data, in the ame iitate, but with its leaves disappearing ; 4, Itamalina calicaris, 

 with the stem nearly lost, and the shields borne upon irregular unsymmetrical 

 expansions; 5, Slicta heibacea, with the stem entirely lost, and the leaves 

 spreading ,ivcr the surface of the ground ; 0, farmelia pallacmi, with the 

 items and leaves consolidated, and forming only a crust with a definite margin ; 

 7, Opfgrnplia ttrifta, in which nothing is formed except the letter-like fruc- 

 tification. 



Lichens are distributed over all parts of the world, forming in the 

 polar and similar regions a food for animals and man. Cladonia 

 ranyiferina supports the Rein-Deer ; Cetraria hlandica furnishes the 

 nutritious Iceland Moss of the druggists' shops ; and various species 



of Gyrophora, under the name of Tripe de Roche, form a part of the 

 supply of food scantily furnished by nature for the Canadian hunter. 

 In warmer countries they acquire a, firmer consistence, and appear to 

 form secretions of a peculiar kind in much greater abundance than 

 in the northern parts of the world. Orchall, for example, grows in 

 Great Britain and the Canaries, and botanists can detect no external 

 differences between the plants of these two countries ; yet in the 

 former its dyeing matter is secreted so abundantly that Canary samples 

 fetch from 2501. to 350?. a ton in the market, while the English are 

 unsaleable. 



The order consists of between 50 and 60 genera, with about 2400 

 species, which are divided by Fries into 4 sub-orders Hymenothalami, 

 Gasterothalami, IdiotJialami, and Coniothalami : to these some system- 

 atists add Byssaceie. [BYSSACE^E.] These are again subdivided into 

 several tribes, each tribe comprising several genera. 



The tribe Usneacece is characterised by having an open disc, and 

 being destitute of an hypothallus. It embraces the genera Usnea, 

 Everina, Roccella, Ramalina, and Cetraria. Several species of Usnea 

 are known by the common names of Jupiter's Beard, Tree-Beard, &c., 

 on account of their hair-like appearance. They are amongst the most 

 common of the Lichens which cover the trunks of aged trees, and give 

 to them a picturesque appearance. Usnea plicata is a common species 

 on old trees, park-palings, &c., and has been recommended as a remedy 

 in hooping-cough. 



The species of the genus Everina are common in Great Britain. 

 One of them, E. pranaitri, has a peculiar power of imbibing and 

 retaining odours, and on this account is in much request as an ingre- 

 dient in perfumed cushions and sweet-pots. It has been recommended 

 as a remedy in pulmonary affections. It is frequently found on the 

 oak and other trees. Evelyn says "of it : " This very moss of the oak 

 that is white composes the choicest cypress-powder, which is esteemed 

 good for the head ; but impostors familiarly vend other mosses under 

 that name, as they do the fungi for the true agaric (excellent for 

 haemorrhages and fluxes), to the great scandal of physic." It is said 

 that E. vulpina is poisonous to wolves, hence its name, but little is 

 known of its real properties. 



The genus Ramalina is found associated with the last two on the 

 trunks and branches of trees, especially of the fir, the birch, the ash, 

 the oak, the sloe, and the hawthorn. Lightfoot says that the 

 R. icopuiorum " will dye a red colour, and promises in that intention 

 to rival the famous Lichen Roccella, or Argol, which is brought from 

 the Canary Islands." 



For the properties and uses of the species of Roccella and C'etraria 

 see ABCHIL, in ARTS AND Sc. Div., and CETRABIA. 



The tribe Parmeliacece is characterised by a horizontal thallus. To 

 it belong the genera Pdtigera, Sticta, Bon-era, Parmelia, &c. 



Two of the species of Peltigera, P. canina and P. aphtkosa, have 

 been used in medicine : the former as a remedy in hydrophobia ; the 

 latter is boiled in milk and administered in the thrush. 



The species of Parmelia are exceedingly numerous ; one of the most 

 common throughout Europe is the P. parietina, Yellow Moss. The 

 thallus and shields are both of a yellow colour ; and Lightfoot says, 

 " It is affirmed to dye a good yellow or orange colour if mixed with 

 alum." It has also a very bitter taste, which has caused it to be used 

 as a tonic in medicine, and it has been recommended as a remedy in 

 intermittent fever. P. tartarea (Lecanora tartarea) yields the dye 

 known by the name of Cudbear. [PARELLA.] P. Parella (Lecanora 

 parella) affords the substance known as Litmus, or Laemus. [Limus, 

 in ARTS AND Sc. Div.] 



One of the species of the genus Sticta, S, pulmonacea, has been used 

 as a substitute for the Iceland Moss. [CETHARIA.] It is used in 

 Siberia for giving a bitter flavour to beer. It is a native of Great 

 Britain, and is found on the trunks of trees in mountainous districts, 

 almost entirely covering them with its large shaggy fronds. 



A species of Borrera [BORHERA], B. furfuracea, is reputed to be 

 astringent and febrifuge. It is found on the trunks and branches of 

 old trees, especially when decaying, and on old pales. 



The tribe Lecidina: embraces the important genus Cladonia 

 [CLADONIA], and also Cenomyce and Scyphophorus, which are often 

 only regarded as subgenera of Cladonia. The S. pyxidatus and 

 S. coccifertu are elegant lichens, having their apothecia elevated above 

 the thallus in the form of little cups, those of the latter species being 

 coloured scarlet. They have both been used in medicine as astringent 

 and febrifuge. 



The tribe Sp!uero]>horeie contains the genera Spharophoron, Plocaria, 

 and Indium. They are an exceedingly elegant group of Lichens, but 

 the species have not been much used for economical purposes, hidium 

 corallinum is said to be rich in colouring matter. 



The genera Endocarpon and Purina belong to the tribe Endocarpece. 

 The species of the former genus are found on rocks and stones, whilst 

 those of the latter are interesting as forming distinguishing marks 

 between various kinds of barks used in medicine. Fee, in his ' Me'thode 

 Lich<!nographique,' has endeavoured to apply a knowledge of the 

 various species of Lichens to the distinguishing not only between the 

 bark of different species of Cinchona, &c., but also between good and 

 bad barks of the same species. 



The principal genus of the tribe Verrucarince is Verrucaria, of which 

 the species are very numerous. [VEBRUCAHIA.] 



