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west. A further distinction into Libya interior and exterior is also known. The former (7) kvrbc) included the interior (known and unknown) of the See also:

CONTINENT (from Lat. continere, "to hold together "; hence " connected," " continuous ")

continent, as contrasted with the N. and N.E. portion; the latter (i no), called also simply Libya, or Libyae nomos), between Egypt and Marmarica, was so called as having once formed an See also:

EGYPTIAN

Egyptian " See also:

NOME

nome." See AFRICA, Gonidia.—It has been made clear above that the gonidia are nothing more than algal cells, which have been ensnared by fungal hyphae and made to develop in captivity (fig. I). Funf See also:

STUCK, FRANZ (1863— )

stuck gives ten See also:

FREE

free living See also:

ALGAE

algae which have been identified as the gonidia of See also:

LICHENS

lichens. Pleuro- coccus (Cystococcus) humicola in the See also:

MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority of lichens, e.g.

Usnea, Cladonia, Physcia, Parmelia, See also:

CALI

Cali- cium, many See also:

SPECIES

species of Lecidea, &c., Trentepohlia (Chroolepus) umbrina in many species of Verrucaria, Graphidieae and Lecidea; See also:

PALMELLA

Palmella botryoides in Epigloea; Pleurococcus vulgaris in Acarospora, Dermato- carpon, Catillaria; Dactylococcus infusionum in Solorina, Ntphromia; into one another, and the distinction is not of classificatory value. In See also:

EXTERNAL

external See also:

FORM (Lat. forma)

form the heteromerous thallus presents the following modifications. (a) The foliaceous (See also:

LEAF (O. Eng. leaf, cf. Dutch loof, Ger. Laub, Swed. lof, &c.; possibly to be referred to the root seen in Gr. Ma-eta, to peel, strip)

leaf-like) thallus, which may be either peltate, i.e. rounded and entire, as in Umbilicaria, &c., or variously lobed and laciniated, as in Sticta, Parmelia, Cetraria (fig. 4), &c. This is the highest type of its development, and is sometimes very considerably See also:

EXPANDED

expanded. (b) The fruticose thallus may be either erect, becoming pendulous, as in Usnea (fig. 5), Ramalina, &c., or prostrate, as in Alectoria jubata, See also:

var. chalybeiformis. It is usually divided into branches and branchlets, bearing some resemblance to a See also:

MINIATURE

miniature See also:

SHRUB

shrub. An erect cylindrical thallus terminated by the See also:

FRUIT (through the French from the Lat. fructus; frui, to enjoy)

fruit is termed a podetium, as in Cladonia (fig. 7). (c) The crustaceous thallus, which is the most See also:

COMMON

common of all, forms a See also:

mere crust on the substratum, varying in thickness, and may be squamose (in Squamaria), radiate (in Placodium), areolate, granulose or pulverulent (in various Lecanorae and Lecideae). (d) The hypophloeodat thallus is often concealed beneath the bark of trees (as in some Verrucariae and Arthoniae), or enters into the See also:

fibres of See also:

wood (as in Xylographa and Nostoc lichenoides in most of rutida in Omphalaria; Lichina, in Peltigera, Pannaria and Stictina; Glbeocapsa polydermatica in Baeomyces and Omphalaria; Sirosiphon pulvinatus in Ephebe pubescens.

The majority of lichens are confined to one particular See also:

KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind of gonidium (i.e. species of alga) but a few forms are known (Lecanora granatina, Solorina crocea) which make use of more than one kind in their development. In the See also:

case of Solorina, for ex-ample, the See also:

PRINCIPAL

principal alga is a See also:

green alga, one of the Palmellaceae, but Nostoc See also:

BLUE (common in different forms to most European languages)

blue-green alga) is also found playing a subsidiary part After See also:

BONNIER, ANGE ELISABETH LOUIS ANTOINE (1749-1799)

Bonnier, from v. Tavel. permission of Gustav See also:

Fischer. 1, Germinating ascospore (sp) 2, Thallus in See also:

PROCESS

process of forma-with branching germ-See also:

TUBE (Lat. tuba)

tube tion. applied to the Cystococcus sp, Two ascospores. See also:

CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell's (a). p, Cystococcus cells. Agyrium), being indicated externally only by a very thin film (See also:

FIGS

figs. 3, 4, 5, 6, 7 and 8). In See also:

COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour also the thallus externally is very variable. In the dry and more typical See also:

state it is most frequently See also:

white or whitish, and almost as often greyish or greyish See also:

GLAUCOUS (Gr. yAavK6s, bright, gleaming)

glaucous.. Less commonly it is of different shades of See also:

brown, red, yellow and See also:

black. In the moist state of the thallus these See also:

COLOURS, MILITARY

colours are much less apparent, as the textures then become more or less trans-lucent, and the thallus usually prevents the greenish colour of the gonidia (e.g.

Parmelia Borreri, Peltidea ophthosa, Umbilicaria pustulata and pulverulent Lecideae). The thallus may be free upon the See also:

SURFACE

surface of the substratum (e.g. Collema) or may be fixed more or less closely to it by See also:

SPECIAL

special hyphae or rhizoids. These may penetrate but slightly into the substratum, but the connexion established may be so See also:

close that it is impossible to remove the thallus from the substratum without injury (e.g. Physcia, Placodium). In some cases the rhizoids are See also:

UNITED

united together into larger strands, the rhizines. The typical heteromerous thallus shows on See also:

section a peripheral, thin and therefore transparent, layer, the cortical layer, and centrally a See also:

mass of denser See also:

TISSUE (Fr. tissu, tissue, participle of tisser, Lat. texere, to weave)

tissue the so-called medullary layer, between these two layers is the algal See also:

ZONE (Gr. 'WV77, a girdle, from 'wvvLvay to gird)

zone or gonidial layer (figs. 8 and 9). The See also:

TERM

term epithallus is sometimes applied to the superficial dense portion of the cortical layer and the term hypothallus to the layer, when specially modified, in immediate contact with the substratum; the hypothallus is usually dark or blackish. The cylindrical branches of the fruticose forms are usually radially symmetrical, but the flattened branches of these forms and also the thalli of the foliaceous form show a difference in the cortex of the upper and See also:

LOWER

lower See also:

side. The cortical layer is usually more See also:

DEVELOPED

developed on the side towards the See also:

LIGHT

light, while in many lichens this is the only side provided with a cortical layer. The podetia of some species of Cladonia possess no cortical layer at all.

The surface of the thallus often exhibits out-growths in the form of warts, hairs, &c. The medullary layer, which usually forms the See also:

main part of the thallus, is distinguished from the cortical layer by its looser consistence and the presence in it of numerous, large, See also:

air-containing spaces. From Strasburger's Lehrbuch der Botanik, by 9 After See also:

Sachs, from De Bary's Vergleichende Morphologic and Biologic der Pilze, Mycetozoen and Bacterien, by permission of Wilhelm Engelman. the Collemaceae; Rivularia &c., Polycoccus punctiformis From Strasburger's Lehrbuch See also:

SION [Ger. Sitten]

sion of Gustav Fischer. ap, Apothecium. der Botanik, by permis- (a as gonidia. In L. granatina the See also:

PRIMARY

primary alga is Pleurococcus, the secondary, Gleococapsa. Cephalodia.—In about roo species of lichens See also:

PECULIAR

peculiar growths are developed in the interior of the thallus which cause a slight See also:

PROJECTION

projection of the upper or lower surface. These structures are known as cephalodia and they usually occupy a definite position in the thallus. They are distinguished by possessing as gonidia algae See also:

FOREIGN

foreign to the See also:

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary part of the thallus. The foreign algae are always members of the Cyanophyceae and on the same individual and even in the same cephalodium more than one type of gonidium may be found. The See also:

FUNCTION

function of these peculiar structures is unknown.

Zukal has suggested that they may See also:

PLAY

play the part of See also:

WATER

water-absorbing See also:

ORGANS

organs. The exact relation of gonidia and hyphae has been investigated e s- pecially by Bornet and also by Hedlund, and very considerable See also:

DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences have been shown to exist in different genera. In Physma, Arnoldia, Phylliscum and other genera the gonidia are killed sooner or later by special hyphal branches, haustoria, which See also:

PIERCE, FRANKLIN (1804—1869)

pierce the membrane of the algal cell, penetrate the See also:

PROTOPLASM

protoplasm and absorb the contents (fig. Is, C). In other cases, e.g. Synalissa, Micarea, the haustoria pierce the membrane, but do not penetrate the protoplasm (fig. I1, D). In many other cases, especially those algae possessing Pleurococcus as their gonidia, there are no penetrating hyphae, but merely From Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer. (Nat. See also:

SIZE

size.) A, Sterile. B, With See also:

ASCUS (Gr. &vu5s, a bag)

ascus-fruit at the ends of the branches. special See also:

SHORT, FRANCIS JOB (1857– )

short hyphal branches which are in close contact with the membrane of the algal cell (fig. 3).

See also:

REPRODUCTION

Reproduction. There are three methods of reproduction of the See also:

LICHEN (lichen ruber)

lichen: by fragmentation, by soredia, by the formation of fungal spores. In the first process, portions of thallus containing gonidia may be accidentally separated and so may start new See also:

PLANTS

plants. The second method is only a special process of fragmentation. The soredia are found in a large number of lichens, and consist of a single gonidium or See also:

groups of gonidia, surrounded by a sheath and hyphae. They arise usually in the gonidial layer of the thallus by See also:

DIVISION (from Lat. dividere, to break up into parts, separate)

division of the gonidia and the developmentaround them of the hyphal investment; their increase in number leads to the rupture of the enclosing cortical layer and the soredia See also:

ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

escape from the thallus as a powdery mass (fig. 12). Since they are provided with both fungal and algal elements, they are able to develop directly, under suitable conditions, into a new thallus. The soredia are the most successful method of reproduction in lichens, for not only are some forms nearly always without spore-formation and in others the spores laregly abortive, but in all cases the spore represents only the fungal component of the thallus, and its success in the development of a new lichen-thallus depends on the See also:

CHANCE (through the O. Fr. cheance, from the Late Lat. cadentia, things happening, from cadere, to fall out, happen; cf. " case ")

chance See also:

MEETING (from " to meet," to come together, assemble, 0. Eng. metals ; cf. Du. moeten, Swed. mota, Goth. gamotjan, &c., derivatives of the Teut. word for a meeting, seen in O. Eng. Wit, moot, an assembly of the people; cf. witanagemot)

meeting, at the See also:

time of germination, with the appropriate algal component. Conidia.—Contrary to the behaviour of the non-lichen forming Ascomycetes the lichen-See also:

FUNGI (p1. of Lat. fungus, a mushroom)

fungi show very few cases of ordinary conidial formation. Bornet describes free conidia in Arnoldia minitula, and Placodium decipiens and Conidia-formation has been described by Neubner in the Caliciae. Spermatia.—In the majority of genera of lichens small See also:

FLASK

flask-shaped structures are found embedded in the thallus (fig.

13). These were investigated by Tulasne in 1853, who gave them the name spermogonia The lower, ventral portion of the spermogonium is lined by delicate hyphae, the sterigmata, which give origin to See also:

minute colour-less cells, the spermatic The sterigmata are either See also:

SIMPLE

simple (fig. 13, C) or septate—the so-called arthrosterigmata (fig. 13, B). The spermogonia open by a small See also:

PORE

pore at the See also:

APEX

apex, to-wards which the sterigmeta converge and through which the spermatia escape (fig. 13). There are two views as to the nature of the spermatia. In one view they are mere asexual conidia, and the term pycnoconidia is accordingly applied since they are See also:

BORNE, KARL LUDWIG (1786–1837)

borne in structures After Sachs, from De Barys Vergleichende More like the non-sexual phologie and Biotogie der Pilze, Mycetozoen and ycnidia of other fungi. Bacterien, by permission of Wilhelm Engelman. n the other view the FIG. 8.—Usnea barbata. (Mag. nearly too spermatia are the male times.) sexual cells and thus A, See also:

OPTICAL

Optical See also:

LONGITUDINAL

longitudinal section of the ex- are rightly named; it tremity of a thin See also:

BRANCH (from the Fr. branche, late Lat. branca, an animal's paw)

branch of the thallus should, however, be which has become transparent in pointed out that this See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution of potash.

was not the view of B, Transverse section through a stronger Tulasne, though we owe branch with the point of origin of an to him the designation See also:

ADVENTITIOUS (from Lat. adventicius, coming from abroad)

adventitious branch (sa). which carries with it r, Cortical layer. the sexual significance. m, Medullary layer. The question is one x, Stout See also:

AXILE

axile strand. very difficult to See also:

settle g, The algal zone (Cystococcus). owing to the fact that s, Apex of the branch. the majority of sper- matia appear to be functionless. In favour of the conidial view is the fact that in the case of Collema and a few other forms the spermatia have been made to germinate in artificial cultures, and in the case of Caliciu'm parietinum Moller succeeded in producing a spermogonia bearing thallus from a spermatium. For the germination of the spermatia in nature there is only the observation of Hedlund, that in Catillaria denigrate and C. prasena a thallus may be derived from the spermatia under natural conditions. In relation to the view that the spermatia are sexual cells, or at least were primitively so, it must be pointed out that although the actual See also:

FUSION

fusion of the spermatial See also:

NUCLEUS (Lat. for the kernal of a nut, nux, the stone of fruit)

nucleus with a See also:

FEMALE

female nucleus has not been observed, yet in a few cases the spermatia have been seen to fuse with a projecting portion (trichogyne) of the ascogonium, as in Collema and Physcia, and there is very strong circumstantial See also:

EVIDENCE (Lat. evidentia, evideri, to appear clearly)

evidence that fertilization takes See also:

PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place (see later in section on development of ascocarp). The resemblance of the spermatia and spermogonia to those of Uredineae should be pointed out, where also there is consider-able evidence for their See also:

ORIGINAL

original sexual nature, though they appear in that See also:

GROUP

group to be functionless in all cases. The observations of Moller, &c., on the germination cannot be assumed to negative. the sexual See also:

HYPOTHESIS (from Gr. inrorcOivat, to put under; cf. Lat. suppositio, from sub-ponere)

hypothesis for the sexual' cells of Ulothrix and Ectercar pus, for example From Strasburger's Lehrbuch der Beatnik, by permission of Gustav Fischer. From Strasburger's Lehrbuch der Botanik, by per-See also:

MISSION

mission of Gustav Fischer.

t, Scales of thallus. primary x s are able to develop with or without fusion. The most satisfactory view in the See also:

PRESENT

present state of our knowledge seems to be that the spermatia are male cells which, while retaining their fertilizing See also:

ACTION

action in a few cases are now mainly functionless. The female sexual organs, the ascogonia, would thus in the majority of cases develop by the aid of some reduced sexual process or the ascocarps be. developed without relation to sexual organs. A further See also:

ARGUMENT

argument in sup-See also:

PORT

port of this view is that it is in See also:

COMPLETE

complete agreement with what we know of the sexuality of the ordinary, free-living ascomycetes, where we find both normal and reduced forms (see FUNGI). Fruit Bodies.—We find two See also:

CHIEF (from Fr. chef, head, Lat. caput)

chief types of fruit bodies in the lichens, the perithecium and apothecium; the first when the fungal -d See also:

ELEMENT (Lat. elementum)

element is a member of the Pyrenomycetes division of the Ascomycetes, the second when the fungus belongs to From Beitrcge zur Wisse, schafilichgn Botanik. the Discomycetes division. Lichen Thallus. the. Basidiolichens—in a, Upper cortical layer. d, Lower cortical layer. c, Medullary layer. b, Gonidial layer.be added. They present various shapes, of which the following are the principal: (a) peltate, which are large, rounded, without any distinct thalline margin' (e.g.

Usnea, Peltigera) ; (b) lecanorine, or scutelliform, which are orbicular and surrounded by a distinct, more or less prominent thalline margin (e.g. Parmelia, Lecanora), having sometimes also in addition a proper one t (e.g. Thelotrema, Urceolaria) ; (c) lecideine, or patelliform, which are typically orbicular1 with only a proper margin (e.g. Lecidea), sometimes obsolete, and which are occa- sionally irregular in shape, angular or flexuose (e.g. Lecidea jurana, L. myrmecana), or complicated and _ gyrose (e.g. Gyro- See also:

PHORA

phora), and even After Schwendener, from De Bary's Vergleichende Mor s t i p i t a t e (e.g. phologie See also:

PERM

perm o Bilo size a Mycelozoen and Becterien. Baeomyces) ; (d) larelliform, which FIG. 12.—Usnea baebata. (Mag. more than are of very irregu- soo times.) See also:

lar figure, elon c, An isolated mature soredium, with an algal gated, branched or cell (Pleurococcus) in the envelope or hyphae. flexuose, with only d, Another with several algal cells in optical a proper margin longitudinal section. (e.g. Xylographa, e, ,f, Two soredia in the See also:

ACT (Lat. actus, actum)

act of germinating; the Graphis, &c.) or yphal envelope has grown out below into none (e.g. some rhizoid branches, and above shows already Arthonise), and the structure of the apex of the thallus (see often very variable fig. 9).

even in the same species. In colour the apothecia are extremely variable, and it is but rarely that they are the same colour' as the thallus (e.g. Usnea, Ramalina). Usually they are of a different colour, and may be black, brown, yellowish, or also less frequently See also:

rose-coloured, rusty-red, See also:

orange-reddish, See also:

SAFFRON (Arab. za'faran)

saffron, or of various intermediate shades. Occasionally in the same species their colour is very variable (e.g. Lecanora metaboloides, Lecidea decolorans), while sometimes they are white or glaucous, rarely greenish, pruinose. Lecideine apothecia, which are not black, but otherwise variously coloured, are termed biatorine. The two principal parts of which an apothecium consists are the hypothecium and the hymenium, or theciui. The hypothecium is the basal part of the apothecium on which the hymenium is borne; the latter consists of See also:

ASCI

asci (thecae) with ascospores, and paraphyses. The paraphyses (which may be absent entirely in the Pyrenolichens) are erect, colourless filaments which are which the fungus is a mem- ber of the Basidiomycetes, we have the fructification characteristic of that class of fungi: these are, dealt with separately. The perithecium is very See also:

CONSTANT, BENJAMIN (1845-1902)

constant in form and since the gonidia take no part See also:

variations are of value in See also:

CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

classification some more details may C in After Tulasne, from De Bary's Vergleichende Morphologic end Biologic der Pate, Mycetozoen and Baoterien, by permission of Wilhelm Engelmann. B 390 times, C highly magnified.) A, A See also:

VERTICAL (from Lat. vertex, highest point)

vertical median sec- w, Its See also:

wall from which tion through a sper- proceed sterigmata mogonium imbedded with See also:

rod-like sper- in the thallus. matia (s).

o, Upper rind. m, Medullary hyphae of u, Under rind. [thallus. the thallus. m, Medullary layer of the C, Cladonia novae A ngliae, B, Portion of a very thin Delise; sterigmata section from the See also:

BASE

base with spermatia from of the spermogonium. the spermogohium. usually dilated and coloured at the apex; the apices are usually cemented together into a definite layer, the epithecium (fig. 14). The spores themselves may be unicellular without a septum or multicellular with one or more septa. Sometimes the two cavities are restricted to the two ends of the spore, the polaribilocular type and the two loculi ma,y be united and Biologic der See also:

PARE, AMBROISE (1510-1590)

Pare, Mycetowas end t The thalline margin (margo thallinus) is the projecting edge of a special layer of thallus, the amphithecium, See also:

ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round the actual apothecium; the proper margin (margo proprius) is the projecting edge of the apothecium itself. After Bornet, from De Bary's Vergleichende Morphologic Bacterien, by permission of Wl cti Engelmin. A, Pleurococcus, Ag. (Cystococcus, Nag.) C, Nostoc from the thallus of Physma attacked by the germ-tube from a chalazanum. spore of Physiea.parietina. D, Gloeocapsa from the thallus of B, Scytonema from the thallus of Synalissa Symphorea. Stereocaulea tamtutosum.

E, Pleurococcus Sp. (Cystococcus) from the thallus of Cladonia furcata. in the formation of this See also:

ORGAN

organ or that of the apothecium it has the general' strtictntre characteristic of that division of fungi. The a otheciai,' though of the normal fungal type and ukually disk-shapeld, are'somewhtlt more variable, and since the as is necessarily the case where the ,ascogonia have no trichogynes or the spermatia are absent. In these cases we should expect to find some reduced process of fertilization similar to that of by a narrow channel (fig. 15). At other times the spores are divided by both transverse and longitudinal septa producing the muriform (murali-divided) spore so called from the resemblance of the individual See also:

chambers to the stones in a wall. The very large single spores of Pertusaria have been shown to contain numerous nuclei and when they germinate develop a large number of germ tubes. Development of the Ascocarps.—As the remarks on the nature of the spermatia show, the question of the sexuality of the lichens has been hotly disputed in common with that of the See also:

REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest of the Ascomycetes. As indicated above, the See also:

WEIGHT

weight of evidence seems to favour what has been put forward in the case of the non-lichenforming fungi (see FUNGI), that in some cases the ascogonia develop as a result of a previous fertilization by spermatia, in other cases the ascogonia develop without such a See also:

union, while in still other Epithecium Asci Proper margin Thecium (Hymenium) .~ Tbafrine margin i - _==_Mgd ~lld— ~Ypofhec,nm_ __ After Darbishire, from Berichte der deutschen botanischen Gesellschaft, by permission of Bomtraeger & Co. cases the reduction goes still farther and the ascogenous hyphae instead of developing from the ascogonia are derived directly from the vegetative hyphae. The first exact knowledge as to the origin of the ascocarp was the See also:

WORK

work of See also:

Stahl on Collema in 1877.

He showed that the archicarp consisted of two parts, a lower coiled portion, the ascogonium, and an upper portion, the trichogyne, which projected from the thallus. Only when a spermatium was found attached to the trichogyne did the further development of the ascogo.nium take place. From these observations he See also:

drew the natural conclusion that the spermatium was a male, sexual cell. This view was hotly contested by many workers and it was sought to explain the trichogyne—without much success—as a See also:

RESPIRATORY

respiratory organ, or as a See also:

BORING

boring organ which' made a way for the developing apothecium. It was, not till 1898, however, that Stahl's work received See also:

CONFIRMATION (Lat. confirmatio, from confirmare, to establish, make firm)

confirmation and addition at the hands of See also:

BAUR, FERDINAND CHRISTIAN (1792-1860)

Baur (fig. 16). The latter showed that in Collema crispum there are two kinds of thalli, one with numerous apothecia, the other quite sterile or bearing only a few. The sterile thalli possessed no spermogonia, but were found to show sometimes as many as moo archicarps with trichogynes; yet none orvery few came to maturity. The fertile thalli were shown Q to See also:

bear either spermogonia or to be in immediate See also:

con- nexion with spermogonia- bearing thalli. Furthermore Baur showed that after the fusion of the spermatium with the trichogyne the transverse walls of that organ became perforated. There was thus very strong circumstantial evidence in favour of fertilization, although the male nucleus was not traced. The further work of Baur, and that of Darbishire, Funfstuck and See also:

Lindau, have shown that in a number of other cases trichogynes are present.

Thus ascogonia with trichogynes have been observed in Endocarpon, Collema, Pertusaria, Lecanora, Gyrophora, Parmelia, Ramalina, Physcia, Anaptychia and Cladonia. In Nephroma, Peltigera, Peltidea and Solorina a cogonia without trichogynes have been observed. In Collema and a form like Xanthoria parietina it is probable that actual fertilization takes place, and possibly also in some of the other forms. It is probable, however, that in the majority of cases the ascogonia develop without normal fertilization, Kumaria granulata among the ordinary Ascomycetes, where in the See also:

ABSENCE (Lat. absentia)

absence of the antheridia the female nuclei fuse in pairs. In other lichens we should expect to find the ascogenous hyphae arising directly from the vegetative hyphae as in Humaria rulilans among the ordinary fungi, where the process is associated with, the fusion of vegetative nuclei. It is possible that So- lorina saccata belongs to this class.' Cytological details of nuclear behaviour among the lichens are, however, difficult to obtain owing to the slow growth of these forms and the often refractory nature of the material in the See also:

MATTER

matter of preparation for microscopical examination. Ejection of Spores.'–The spores are ejected from the apothecia and See also:

PERI, JACOPO (1561–16 ?)

peri thecia as in the fungi by forcible ejaculation from the asci. In the majority of forms it is clear that the soredia rather than the ascospore must play the more important part in lichen See also:

DISTRIBUTION (Lat. distribuere, to deal out)

distribution as the development of the ordinary spores is dependent on their finding the proper alga on the sub-stratum on which they happen to fall. In a number of forms (Endocarpon pusillum, Stigmaatonima cataleptum, various species of Staurothele), however, there is a special arrangement by which the spores are, on ejection, associated with gonidia. In these forms gonidia are found in connexion with the See also:

young fruit; such algal cells undergo numerous divisions becoming very small in size and penetrating into the hymenium among the asci and paraphyses. When the spores are thrown out some of these hymenial gonidia, as they are called, are carried with them. When the spores germinate the germ-tubes ,surround the algal cells, which now in-crease in size and become the normal gonidia of the thallus.

Basidiolichens. As is clear from the above, nearly all the lichens are, produced by the association of' an ascomycetous fungus with algae. For some obscure See also:

REASON (Lat. ratio, through French raison)

reason the Basidiomycetes do not readily form lichens, so that only a few forms are known in which the fungal element is a member of this See also:

FAMILY

family. known genera are Cora A and Dictyonema; Corella, whose hymenium is un- ? known, is also placed here by Wainio. The so-called Gasterolichens, Trichocoma and Emericella, have been shown to be merely ascomycetous fungi. Clitvaria mucida, however, has apparently some claims to be considered as a Basidiolichen, since the base of the fruit See also:

BODY

body and the thallus from which it arises, according to Coker, always shows a mixture of hyphae and algae. The best-known species is Cora pavonia, • which is found in tropical regions growing on the See also:

BARE

bare See also:

earth and on trees; the gonidia belong to the genus Chroococcus while the fungus belongs, apparently, to the Thelephoreae (see FUNGI). This lichen seems unique in the fact that thefungal element is a)so found growing and fruiting entirely' devoid of algae, while in the cium of Xanthoria parietina. a, Paraphyses. b, Asci (thecae) with bilocular spores. c, Hypothecium. A After E. Baur, from Strasburger's Lehrbech der Botenik, by per-mission of Gustav Fischer.

A, Carpogonium, c, with its trichogyne i. B, Apex of the trichogyne with the spermatium s, attached. The two best- B From Strasburger's Lehrbuck der Bokanik, by permission of Gustav Fischer. ascolichens the fungus portion seems to have become so specialized to its symbiotic mode of See also:

LIFE

life that it is never found growing independently. The genus Dictyonema has gonidia belonging to the blue-green alga, Scytonema. When the fungus predominates in the thallus it has a See also:

BRACKET

bracket-like mode of growth and is found projecting from the branches of trees with the hymenium on the under side. When the alga is predominant it forms felted patches on the bark of trees, the Laudatea form. It is said that the fungus of Cora pavonia and of Dictyonema is identical, the difference being in the nature of the alga. Mode of Life. Lichens are found growing in various situations such as bare earth, the bark of trees, dead wood, the surface of stones and rocks, where they have little competition to fear from ordinary plants. As is well known, the lichens are often found in the most exposed and arid situations; in the extreme polar regions these plants are practically the only See also:

VEGETABLE

vegetable forms of life. They owe their capacity to live under the most in-hospitable conditions to the dual nature of the organism, and to their capacity to withstand extremes of See also:

HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat, See also:

COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

cold and drought without destruction.

On a bare rocky surface a fungus would See also:

die from want of organic substance and an alga from drought and want of See also:

MINERAL

mineral substances. The lichen, however, is able to grow as the alga supplies organic See also:

food material and the fungus has developed a See also:

BATTERY (Fr. batterie, from battles, to beat)

battery of acids (see below) which enable it actually to dissolve the most resistant rocks. It is owing to the See also:

POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power of disintegrating by both See also:

MECHANICAL

mechanical and chemical means the rocks on which they are growing that lichens play such an important part in See also:

SOIL

soil-See also:

PRODUCTION (Lat. productionem, from producere, to pro-duce)

production. The resistance of lichens is extraordinary; they may be cooled to very See also:

low temperatures and heated to high temperatures without being killed. They may be dried so thoroughly that they can easily be reduced to See also:

POWDER (through O. Fr. puldre, modern poudre, from Lat. pulvis, pulveris, dust)

powder yet their vitality is not destroyed but only suspended; on being supplied with water they absorb it rapidly by their general surface and renew their activity. The life of many lichens thus consists of alternating periods of activity when moisture is plentiful, and completely suspended animation under conditions of dryness. Though so little sensitive to drought and extremes of temperature lichens appear to be very easily affected by the presence in the air of noxious sub-stances such as are found in large cities or manufacturing towns. In such districts lichen vegetation is entirely or almost entirely absent. The growth of lichens is extremely slow and many of them take years before they arrive at a spore-bearing See also:

STAGE (Fr. 6/age; from Lat. stare, to stand)

stage. Xanthoria parietina has been known to grow for See also:

FORTY

forty-five years before bearing apothecia. This slowness of growth is associated with great length of life and it is probable that individuals found growing on hard See also:

mountain rocks or on the trunks of aged trees are many hundreds of years old. It is possible that specimens of such See also:

long-lived species as Lecidea geographica actually outrival in See also:

LONGEVITY

longevity the See also:

OLDEST

oldest trees.

Relation of Fungus and Alga. The relation of the two constituents of the lichen have been briefly stated in the beginning of this See also:

ARTICLE (from Lat. articulus, a joint)

article. The relation of the fungus to the alga, though it may be described in general terms as one of symbiosis, partakes also somewhat of the nature of See also:

PARASITISM

parasitism. The algal cells are usually controlled in their growth by the hyphae and are prevented from forming zoospores, and in some cases, as already described, the algal cells are killed sooner or later by the fungus. The fungus seems, on the other See also:

hand, to stimulate the algal cells to special development, for those in the lichen are larger than those in the free state, but this is not necessarily adverse to the See also:

IDEA (Gr. Ibia, connected with i&eiv, to see; cf. Lat. species from specere, to look at)

idea of parasitism, for it is well known that an increase in the size of the cells of the See also:

HOST

host is often the result of the attacks of parasitic fungi. It must be borne in mind that the exact nutritive relations of the two constituents of the lichen have not been completely elucidated, and that it is very difficult to draw the See also:

LINE

line between symbiosis and parasitism. The lichen algae are not alone in their specializa-tion to the symbiotic (or parasitic) mode of life, for, as stated earlier, the fungus appear in the majority of cases to have completely lost the power of See also:

INDEPENDENT

independent development since with very rare exceptions they are not found alone. They also differ very markedly from free living fungi in their chemical reactions. See also:

Chemistry of Lichens. The chemistry of lichens is very complex, not yet fully investigated and can only be very briefly dealt with here. The wall of the hyphae of the fungus give in the young state the ordinary reactions of See also:

CELLULOSE

cellulose but older material shows somewhat different reactions, similar to those of the so-called fungus-cellulose. In many lichen-fungi the wall shows various chemical modifications.

In numerous lichens, e.g. Cetraria islandica, the wall contains Lichenin (See also:

C6H,,05), a gummy substance which swells in cold water and dissolves in hot. Besides this substance, a very similar one, Isolichenin, is also found which is distinguished from lichenin by the fact that it dissolves in cold water and turns blue under the reaction of See also:

IODINE (symbol I, atomic weight '26.92)

Iodine. See also:

CALCIUM [symbol Ca, atomic weight 40.0 (o= x6)]

Calcium oxalate is a very common substance, especially in crustaceous lichens; fatty oil in the form of drops or as an infiltration in the membrane is also common; it sometimes occurs in special cells and in extreme cases may represent 90% of the dry substance as in Verrucaria calciseda, Biatora immersa. Colouring Matters.—Many lichens, as is well known, exhibit a vivid colouring which is usually due to the incrustation of the hyphae with crystalline excretory products. These excretory products have usually an See also:

ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid nature and hence are generally known as lichen-acids. A large number of these acids, which are mostly See also:

BENZENE, C6H6

benzene derivatives, have been isolated and more or less closely investigated. They are characterized by their insolubility or very slight solubility in water; as examples may be mentioned erythrinic acid in Roccella and Lecanora; evernic acid in species of Evernia, Ramalina and Cladonia; lecanoric acid in Lecanora, G rophora. The so-called chrysophanic acid found in Xanthoria (Physcia) parietina is not an acid but a quinone and is better termed physcion. Colour Reactions of Lichens.—The classification of lichens is unique in the fact that chemical colour reactions are used by many lichenologists in the discrimination of species, and these reactions are included in the specific diagnoses. The substances used as tests in these reactions are See also:

CAUSTIC (Gr. rcavvraubs, burning)

caustic potash and calcium hypochlorite; the former being the substance dissolved in an equal weight of water and the latter a saturated See also:

EXTRACT (from Lat. extrahere, to draw out)

extract of See also:

BLEACHING

bleaching powder in water. These substances are represented by lichenologists by the signs K and CaCl respectively, and the presence or absence of the colour reactions are represented thus, K+, CaCl+, or K—, CaCl—.

If the cortical layer should exhibit See also:

POSITIVE (or PORTABLE) ORGAN

positive reaction and the medulla of the same species a negative reaction with both reagents, the result is represented thus, KCaCl. If a reaction is only produced after the consecutive addition of the two reagents, this is symbolized by K(CaCI) +. A solution of iodine is also used as a test owing to the blue or See also:

WINE (Lat. vinum, Gr. oivos)

wine-red colour which the thallus, hymenium or spores may give with this reagegt. The objection to the case of these colour reactions is due to the indefinite nature of the reaction and the doubt as to the constant presence of a definite chemical See also:

compound in a given species. A yellow colour with causticpotash solution is produced not only by atranoric acid but also by evernic acid, thamnolic acid, &c. Again in the case of Xanthoria parietina vulpinic acid is only to be found in young thalli growing on See also:

sand-See also:

stone; in older forms or in those growing on another substratum it is not to be detected. A similar relation between oil formation and the nature of the substratum has been observed in many lichens. Considerations such as these should make one very wary in placing reliance on these colour reactions for the purposes of classification. Economic Uses of Lichens. In the arts, as food and as See also:

MEDICINE

medicine, many lichens have been highly esteemed, though others are not now employed for the same purposes as formerly. r. Lichens Used in the Arts.—Of these the most important are such as yield, by maceration in See also:

AMMONIA (NH3)

ammonia, the dyes known in See also:

commerce as See also:

ARCHIL (a corruption of " orchil," Ital. oricello, the origin of which is unknown)

archil, cudbear and See also:

LITMUS (apparently a corruption of lacmus, Dutch lacmoes, lac, lac, and moes, pulp, due to association with " lit," an obsolete word for dye, colour; the Ger. equivalent is Lac/emus, Fr tournesol)

litmus.

These, however, may with propriety be regarded as but different names for the same pigmentary substance, the variations in the See also:

CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character of which are attributable to the different modes in which the See also:

PIGMENTS (Lat. pigmentum, from pingere, to paint)

pigments are manufactured. Archil proper is derived from several species of Roccella (e.g. R. Montaguei, R. tinctoria), which yield a See also:

rich See also:

PURPLE

purple dye; it once fetched a high See also:

price in the See also:

MARKET (Lat. mercatus, trade or place of trade)

market. Of considerable value is the " perelle " prepared from Lecanora parella, and used in the preparation of a red or See also:

CRIMSON

crimson dye. Inferior to this is "cudbear," derived from Lecanora tartarea, which was formerly very extensively employed by the peasantry of north See also:

EUROPE

Europe for giving a See also:

SCARLET

scarlet or purple colour to woollen cloths. By adding certain alkalies to the other ingredients used in the preparation of these pigments, the colour becomes See also:

INDIGO (earlier indico, from Lat. indicum, the Indian sub-stance or dye; the Sans. name was niti, from nila, dark blue, and this through Arab. al-nil, annil, gives " aniline ")

indigo-blue, in which case it is the litmus of the Dutch manufacturers. Amongst other lichens affording. red, purple or brown dyes may be mentioned Ramalina ucopulorum, Parmelia, saxatilis and P. amphalodes, Umbilicaria pusiulata and several species of Gyrophora, Urceolaria scruposa, all of which are more or less employed as domestic dyes. Yellow dyes, again, are derived from Chlorea vulpina, Platysma juniperinum, Parmelia caperata and T. conspersa, Physcia flavicans, Ph. parietina and Ph. lycknea, though like the preceding they do not form articles of commerce, being merely used locally by the natives of the regions in which they occur most plentifully. In addition to these, many See also:

EXOTIC (Gr. EWTIK6s, foreign, from few, outside)

exotic lichens, belonging especially to Parmelia and Sticta (e.g. Parmelia tinctorum, Sticta argyracea), are rich in colouring matter, and, if obtained in sufficient quantity, would yield a dye in every way equal to archil. These pigments primarily depend upon special acids contained in the thalli of lichens, and their presence may readily be detected by means of the reagents already 'noticed.

In the process of manufacture, however, they undergo various changes, of which the chemistry is still but little understood. At one time also some species were used in the arts for supplying a See also:

GUM (Fr. gomme, Lat. gommi, Gr. Kµµ1, possibly a Coptic word; distinguish " gum," the fleshy covering of the base of a tooth, in O. Eng. gbma, palate, cf. Ger. Gaumen, roof of the mouth; the ultimate origin is probably the root gha, to open wide, seen in

gum as a substitute for gum-arabic. These were chiefly Ramalina fraxinea, Evernia prunastri and Parmelia physodes, all of which contain: a consider-able proportion of gummy matter (of a much inferior quality, however, to gum-arable), and were employed in the process of See also:

CALICO

calico-See also:

PRINTING (from Lat. imprimere, O. Fr. empreindre)

printing and in the making of See also:

PARCHMENT

parchment and cardboard. In the 17th See also:

CENTURY (from Lat. centuria, a division of a hundred men)

century some filamentose and fruticuiose lichens; viz. species of Usnea and Ramalina, also Evernia furfuracea and Cladonia rangiferina, were used in the See also:

art of See also:

PERFUMERY (Lat. per, through, and fumare, to smoke)

perfumery. From their supposed aptitude to imbibe and retain odours, their powder was the basis of various perfumes, such as the celebrated " Poudre de Cypre " of the hairdressers, but their employment in this respect has long since been abandoned. 2. Nutritive Lichens.--+Of still greater importance is the capacity of many species for supplying food for See also:

man and beast. This results from their containing starchy substances, and in some cases a small quantity of saccharine matter of the nature of mannite. One of the most useful nutritious species is Cetr See also:

ARIA (Ital. for " air ")

aria islandica, " See also:

ICELAND (Dan. Island)

Iceland See also:

MOSS

moss," which, after being deprived of its bitterness by boiling in water, is reduced to a powder and made into cakes, or is boiled and eaten with See also:

MILK (0. Eng. meoluc; from a common Indo-European root, cf. Lat. mulgere, Gr. ?t dXyetv)

milk by the poor Icelander, whose See also:

SOLE (Solea)

sole food it often constitutes. Similarly Cladonia rangiferina and Cl. sylvatica, the See also:

FAMILIAR (through the Fr. familier, from Lat. familiaris, of or belonging to the familia, family)

familiar " See also:

REINDEER

reindeer moss," are frequently eaten by man in times of scarcity, after being powdered and mixed with See also:

FLOUR

flour. Their chief importance, however, is that in See also:

LAPLAND, or LAPPLAND

Lapland and other northern countries they See also:

SUPPLY (through Fr. from Lat. supplere, to fill up)

supply the See also:

winter food of the reindeer and other animals, who scrape away the See also:

SNOW (in O. Eng. sndw; a common Indo-European word; cf. in Teutonic languages, Ger. Schnee, Du. sneeuw; in Slavonic snieg', Lith. snegas; Gr. vi4a, Lat. nix, nivis, whence the Romanic forms, Ital. neve, Fr. neige, &c.; Ir. and Gael. sneachd; the original

snow and eagerly feed upon them. Another nutritious lichen is the " Tripe de See also:

ROCHE, SIR BOYLE, BART

Roche " of the See also:

ARCTIC (Gr. "ApKroc, the Bear, the northern constellation of Ursa Major)

arctic regions, consisting of several species of the Gyrophorei, which when boiled is often eaten by the See also:

CANADIAN

Canadian hunters and Red See also:

INDIANS, NORTH AMERICAN

Indians when pressed by See also:

HUNGER

hunger.

But the most singular esculent lichen of all is the " See also:

MANNA

manna lichen," which in times of drought and See also:

FAMINE (Lat. fames, hunger)

famine has served as food for large See also:

numbers of men and See also:

CATTLE (Norman Fr. catel, from Late Lat. capitale, wealth or property, a word applied in the feudal system to movable property and particularly to live stock, and surviving in its wider meaning as " chattel " or " chattle ")

cattle in the arid See also:

STEPPES

steppes of various countries stretching from See also:

ALGIERS (Fr. Alger, Arab. Jezair, i.e. The Islands)

Algiers to Tartary. This is derived chiefly from Lecanora esculenta, which grows unattached on the ground in layers from 3 to 6 in. thick over large tracts of See also:

COUNTRY (from the Mid. Eng. contre or contrie, and O. Fr. cuntree; Late Lat. contrata, showing the derivation from contra, opposite, over against, thus the tract of land which fronts the sight, cf. Ger. Gegend, neighbourhood)

country in the form of small irregular lumps of a greyish or white colour. In connexion with their use as food we may observe that of See also:

RECENT

recent years in Scandinavia and See also:

Russia an alcoholic spirit has been distilled 'from Cladonia rangiferina and extensively consumed, especially in seasons when potatoes were scarce and dear. Formerly also Sticta pulmonaria was much employed in See also:

BREWING

brewing instead of hops, and it is said that a Siberian monastery was much celebrated for its See also:

BEER

beer which was flavoured with the See also:

BITTER, KARL THEODORE FRANCIS (1867– )

bitter principle of this species. 3. Medicinal Lichens: During the See also:

MIDDLE

middle ages, and even in some quarters to a much later See also:

period, lichens were extensively used in medicine in various See also:

EUROPEAN

European countries. Many species had a great repute as demulcents, febrifuges, astringents, tonics, purgatives and anthelmintics. The chief of those employedfor one or other, and in some cases for several, of these purposes were Cladonia pyxidata, Usnea barbata, Ramalina farinacea, Evernia prunastri, Cetraria islandica, Sticta pulmonaria, Parmelia saxatilis, Xanthoria parietina and Pertusaria amara. Others again were believed to be endowed with specific virtues, e.g. Peltigera See also:

CANINA, LUIGI (1795-1856)

canina, which formed the basis of the celebrated " pulvis antilyssus " of Dr See also:

Mead, long regarded as a See also:

SOVEREIGN

sovereign cure for See also:

HYDROPHOBIA (Gr. iibwp, water, and 4osos, fear; so called from the symptom of dread of water), or RABIES (Lat. for" madness ")

hydrophobia; Platysma juniperinum, lauded as a specific in See also:

JAUNDICE (Fr. jaunisse, from jaune, yellow), or IUTERUS (from its resemblance to the colour of the golden oriole, of which Pliny relates that if a jaundiced person looks upon it he recovers but the bird dies)

jaundice, no doubt on the similia similibus principle from a resemblance between its yellow colour and that of the jaundiced skin; Peltidea aphthosa, which on the same principle was regarded by the Swedes, when boiled in milk, as an effectual remedy for the aphthae or rash on their See also:

CHILDREN, LAW RELATING TO

children. Almost all of these virtues, general or specific, were imaginary; and at the present See also:

day, except perhaps in some remoter districts of northern Europe, only one of them is employed as a remedial See also:

AGENT (from Lat. agere, to act)

agent. This is the " Iceland moss " of the druggists' shops, which is undoubtedly an excellent demulcent in various dyspeptic and See also:

CHEST (Gr. Kiarl, Lat. cista, O. Eng. cist, test, &c.)

chest complaints.

No lichen is known to be possessed of any poisonous properties to man, although Chlorea vulpina is believed by the Swedes to be so. Zukal has considered that the lichen acids protect the lichen from the attacks of animals; the experiments of Zopf, however, have See also:

CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

cast doubt on this; certainly lichens containing very bitter acids are eaten by mites though some of the acids appear to be poisonous to frogs. Classification. The dual nature of the lichen thallus introduces at the outset a classificatory difficulty. Theoretically the lichens may be classified on the basis of their algal constituent, on the basis of their fungal constituent, or they may be classified as if they were homogeneous organisms. The first of these systems is impracticable owing to the absence of algal reproductive organs and the similarity of the algal cells (gonidia) in a large number of different forms. The second See also:

SYSTEM

system is the most obvious one, since the fungus is the dominant partner and produces reproductive organs. The third system was that of Nylander and his followers, who did not accept the Schwenderian See also:

DOCTRINE

doctrine of duality. In actual practice the difference between the second and third methods is not very great since the fungus is the producer of the reproductive organs and generally the main constituent. Most systems agree in deriving the See also:

major divisions from the characters of the reproductive organs (perithecia, apothecia, or basidiospore bearing fructification), while the characters of the algal cells and those of the thallus generally are used for the See also:

minor divisions. The difference between the various systems lies in the relative importance given to the reproductive characters on the one hand and the vegetative characters on the other. In the system (1854—1855) of Nylander the greater weight is given to the latter, while in more See also:

MODERN

modern systems the former characters receive the more See also:

ATTENTION (from Lat. ad-tendo, await, expect; the condition of being " stretched " or " tense ")

attention.

A brief outline of a system of classification, mainly that of Zahlbruckner as given in Engler and Prantl's Pflanzenfamilien, is outlined below. There are two main divisions of lichens, Ascolichenes and See also:

BASIDIOLICHENES

Basidiolichenes, according to the nature of the fungal element, whether an ascomycete or basidiomycete. The Ascolichenes are again divided into Pyrenocarpeae or Pyrenolichenes and Gymnocarpeae or Discolichenes; the first having an ascocarp of the nature of a perithecium, the second bearing their ascospores in an open apothecium. PYRENOLICHENES See also:

SERIES (a Latin word from serere, to join)

Series I. Perithecium simple not divided. a. With Pleurococcus or Palmella gonidia. Moriolaceae, Verrucariaceae, Pyrenothamnaceae. b. With Chroolepus gonidia. Pyrenulaceae, Paratheliaceae. c.

With Phyllactidium or Cephaleurus gonidia. Strigulaceae. d. With Nostoc or Scytonema gonidia. Pyrenidiaceae. Series II. Perithecia divided or imperfectly divided by See also:

CROSS

cross-walls. Mycoporaceae with Palmella or Chroolepus gonidia. or that of the special See also:

HABITAT (a French word derived from habiter, Lat. habitare, to dwell)

habitat. Thus in the case of saxicolous lichens the mineralogical character of the See also:

rock has of itself little or no See also:

INFLUENCE (Late Lat. influentia, from influere, to flow in)

influence upon lichen growth, which is influenced more especially and directly by their See also:

PHYSICAL

physical properties, such as their capacity for retaining heat and moisture. As a See also:

RULE

rule lichens grow commonly in open exposed habitats, though some are found only or chiefly in shady situations; while, as' already observed, scarcely any occur where the See also:

ATMOSPHERE (Gr. fir µ6r, vapour; orkaipa, a sphere)

atmosphere is impregnated with See also:

SMOKE (from O. Eng. smeocan, to smoke, reek, cf. Dutch meek, Ger. Schmauch, probably allied to Gr. vol9caiv)

smoke. Many species also prefer growing in moist places by streams, lakes and the sea, though very few are normally and probably none entirely, aquatic, being always at certain seasons exposed for a longer or shorter period to the atmosphere (e.g.

Lichina, Leptogiumrivulare, Endocarpon fluviatile, Verrucaria maura). Some species are entirely parasitical on other lichens (e.g. various Lecideae and Pyrenocarpei), and may be peculiar to one (e.g. Lecidea vitellinaria) or common to several species (e.g. Habrothallus parmelierum). A few, generally known as erratic species, have been met with growing unattached to any substratum (e.g. Parmelia revoluta, var. concentrica, Lecanora esculenta); but it can hardly be that these are really free ab initio (vide Crombie in Journ. Bot., 1872, p. 306). It is to the different characters of the stations they occupy with respect to exposure, moisture, &c., that the variability observed in many types of lichens is to be attributed. 2. Distribution.—From what has now been said it will readily be inferred that the distribution of lichens over the surfaceof the globe is regulated, not only by the presence of suitable substrata, but more especially by See also:

CLIMATIC

climatic conditions. At the same time it may safely be affirmed that their See also:

GEOGRAPHICAL

geographical range is more extended than that of any other class of plants, occurring as they do in the coldest and warmest regions—on the dreary shores of arctic and See also:

antarctic seas and in the torrid valleys of tropical climes, as well as on the greatest mountain elevations yet attained by man, on projecting rocks even far above the snow-Iine (e.g.

Lecidea geographica). In arctic regions lichens form by far the largest portion of the vegetation, occurring everywhere on the ground and on rocks, and fruiting freely; while terrestrial species of Cladonia and Stereocaulon are seen in the greatest luxuriance and abundance spreading over extensive tracts almost to the entire exclusion of other vegetation. The lichen See also:

FLORA

flora of temperate regions again is essentially distinguished from the preceding by the frequency of corticolous species belonging to Lecanora, Lecidea and Graphidei. In intertropical regions lichens attain their maximum development (and beauty) in the foliaceous Stictei and Parmeliei, while they are especially characterized by epiphyllous species, as Strigula, and by many peculiar corticole Thelotremei, Graphidei and Pyrenocarpei. Some lichens, especially saxicolous ones, seem to be See also:

COSMOPOLITAN (Gr. Kbvµos, world, and IroXirgs, citizen)

cosmopolitan (e.g. Lecanora subfusca, Cladonia pyxidata); and others, not strictly cosmopolitan, have been observed in regions widely apart. A considerable number of species, European and exotic, seem to be endemic, but further See also:

RESEARCH (O. Fr. recerche, from recercher, re- and cercer, mod. chercher, to search; Late Lat. circare, to go round in a circle, to explore)

research will no doubt show that most of them occur in other climatic regions similar to those in which they have hitherto alone been detected. To give any detailed See also:

account, however, of the distribution of the different genera (not to speak of that of individual species) of lichens would necessarily far exceed available limits. DISCOLICHENES Series I. Coniocarpineae. The paraphyses branch and form a See also:

net-work (capillitium) over the asci, the capillitium and ejected spores forming a long persistent powdery mass (mazaedium). Caliciaceae, Cypheliaceae, Sphaerophoraceae.

Series II. Graphidineae. Apothecia seldom round, usually elongated-ellipsoidal, no capillitium. Arthoniaceae, Graphidiaceae, Roccellaceae. Series III. Cyclocarpineae, Apothecium usually circular, no capillitium. A. Spores usually two-celled, either with a strongly thickened cross-wall often perforated by a narrow See also:

canal or with cross-wall only slightly thickened. In the first case the spores are usually colourless, the second case always brown. Buelliaceae, Physciaceae. 13. Spores unicellular, parallel-multicellular or muriform, usually colourless, cross-walls usually thin.

a Thallus in moist state more or less gelatinous. Gonidia always belonging to the Cyanophyceae, Lichinaceae, Ephebaceae, Collemaceae, Pyrenopsidaceae. Thallus not gelatinous. Coenogoniaceae, Lecideaceae, Cladoniaceae, Lecanoraceae, Pertusariaceae, Peltigeraceae, Stictaceae, Pannariaceae, Gyrophoraceae, Parmeliaceae, Cladoniaceae, Usneaceae.

End of Article: LIBYA

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