CHAPTER X
ECONOMIC AND TECHNICAL
A. LICHENS AS FOOD 395 _a._ Food for insects _b._ Insect mimicry of lichens _c._ Food for the higher animals _d._ Food for man
B. LICHENS AS MEDICINE 405 _a._ Ancient remedies _b._ Doctrine of “signatures” _c._ Cure for hydrophobia _d._ Popular remedies
C. LICHENS AS POISONS 410
D. LICHENS USED IN TANNING, BREWING AND DISTILLING 411
E. DYEING PROPERTIES OF LICHENS 411 _a._ Lichens as dye-plants _b._ The orchil lichen, Roccella _c._ Purple dyes: orchil, cudbear and litmus _d._ Other orchil lichens _e._ Preparation of orchil _f._ Brown and yellow dyes _g._ Collecting of dye-lichens _h._ Lichen colours and spectrum characters
F. LICHENS IN PERFUMERY 418 _a._ Lichens as perfumes _b._ Lichens as hair-powder
G. SOME MINOR USES OF LICHENS 420
APPENDIX 421
ADDENDUM 422
BIBLIOGRAPHY 423
INDEX 448
GLOSSARY
=Acrogenous=, borne at the tips of hyphae; see spermatium, 312.
=Allelositismus=, Norman’s term to describe the thallus of Moriolaceae (mutualism), 313.
=Amorphous cortex=, formed of indistinct hyphae with thickened walls; cf. decomposed cortex.
=Amphithecium=, thalline margin of the apothecium, 157.
=Antagonistic symbiosis=, hurtful parasitism of one lichen on another, 261 _et seq._
=Apothecium=, open or disc-shaped fructification, 11, 156 _et passim_. Veiled apothecium, 169. Closed or open at first, 182.
=Archilichens=, lichens in which the gonidia are bright green (Chlorophyceae), 52, 55 _et passim_.
=Ardella=, the small spot-like apothecium of Arthoniaceae, 158.
=Areola= (areolate), small space marked out by lines or chinks on the surface of the thallus, 73 _et passim_.
=Arthrosterigma=, septate tissue-like sterigma (spermatiophore), 197.
=Ascogonium=, the cell or cells that produce ascogenous hyphae, 180 _et seq._
=Ascolichens=, lichens in which the fungus is an Ascomycete, 159, 173 _et passim_.
=Ascus=, enlarged cell in which a definite number of spores (usually 8) are developed; cf. theca, 157, 184.
=Ascyphous=, podetia without scyphi, 119 _et passim_.
=Biatorine=, apothecia that are soft or waxy, and often brightly coloured, as in _Biatora_, 158.
=Blasteniospore=, see _polarilocular spore_.
=Byssoid=, slender, thread-like, as in the old genus _Byssus_.
=Campylidium=, supposed new type of fructification in lichens, 191.
=Capitulum=, the globose apical apothecium of Coniocarpineae; cf. mazaedium, 319.
=Carpogonium=, primordial stage of fructification, 160, 164 _et passim_.
=Cephalodium=, irregular outgrowth from the thallus enclosing mostly blue-green algae; or intruded packet of algae within the thallus, 11, 133 _et passim_.
=Chrondroid=, hard and tough like cartilage, a term applied to strengthening strands of hyphae, 104, 114.
=Chroolepoid=, like the genus _Chroolepis_ (_Trentepohlia_).
=Chrysogonidia=, yellow algal cells (_Trentepohlia_).
=Cilium=, hair-like outgrowth from surface or margin of thallus, or margin of apothecium, 91.
=Consortium= (consortism), mutual association of fungus and alga (Reinke); also termed “mutualism,” 31, 313.
=Corticolous=, living on the bark of trees, 363.
=Crustaceous=, crust-like closely adhering thallus, 70-79.
=Cyphella=, minute cup-like depression on the under surface of the thallus (_Sticta_, etc.), 11, 126.
=Decomposed=, term applied to cortex formed of gelatinous indistinct hyphae (amorphous), 73-81 _et passim_, 357.
=Determinate=, thallus with a definite outline, 72.
=Dimidiate=, term applied to the perithecium, when the outer wall covers only the upper portion, 159.
=Discoid=, disc-like, an open rounded apothecium, 156.
=Discolichens=, in which the fructification is an apothecium, 160 _et seq._
=Dual hypothesis=, the theory of two organisms present in the lichen thallus, 27 _et seq._
=Effigurate=, having a distinct form or figure; cf. placodioid, 80, 201.
=Endobasidial=, Steiner’s term for sporophore with a secondary sporiferous branch, 200.
=Endogenous=, produced internally, as spores in an ascus, 179; see also under thallus.
=Endolithic=, embedded in the rock, 75.
=Endosaprophytism=, term used by Elenkin for destruction of the algal contents by enzymes of the fungus, 36.
=Entire=, term applied to the perithecium when completely surrounded by an outer wall, 159.
=Epilithic=, growing on the rock surface, 70.
=Epiphloeodal=, thallus growing on the surface of the bark, 77.
=Epiphyllous=, growing on leaves, 363.
=Epithecium=, upper layer of thecium (hymenium), 158.
=Erratic lichens=, unattached and drifting, 259.
=Exobasidial=, Steiner’s term for sporophore without a secondary sporiferous branch, 200.
=Exogenous=, produced externally, as spores on tips of hyphae; see also under thallus.
=Fastigiate cortex=, formed of clustered parallel hyphal branches vertical to long axis of thallus, 82.
=Fat-cells=, specialized hyphal cells containing fat or oil, 75, 215 _et passim_.
=Fibrous cortex=, formed of hyphae parallel with long axis of thallus, 82.
=Filamentous=, slender thallus with radiate structure, 101 _et seq._
=Foliose=, lichens with a leafy form and stratose in structure, 82-97.
=Foveolae=, =Foveolate=, pitted, 373.
=Fruticose=, upright or pendulous thallus, with radiate structure, 101 _et seq._
=Fulcrum=, term used by Steiner for sporophore, 200.
=Gloeolichens=, lichens in which the gonidia are _Gloeocapsa_ or _Chroococcus_, 284, 373, 389.
=Gonidium=, the algal constituent of the lichen thallus, 20-45 _et passim_.
=Gonimium=, blue-green algal cell (Myxophyceae), constituent of the lichen thallus, 52.
=Goniocysts=, nests of gonidia in Moriolaceae, 313.
=Gyrose=, curved backward and forward, furrowed fruit of _Gyrophora_, 184.
=Hapteron=, aerial organ of attachment, 94, 122.
=Haustorium=, outgrowth or branch of a hypha serving as an organ of suction, 32.
=Helotism=, state of servitude, term used to denote the relation of alga to fungus in lichen organization, 38, 40.
=Heteromerous=, fungal and algal constituents of the thallus in definite strata, 13, 68, 305 _et passim_.
=Hold-fast=, rooting organ of thallus, 109, 122 _et passim_.
=Homobium=, interdependent association of fungus and alga, 31.
=Homoiomerous=, fungal and algal constituents more or less mixed in the thallus, 13, 68, 305 _et passim_.
=Hymenial gonidia=, algal cells in the hymenium, 30, 314, 315, 327.
=Hymenium=, apothecial tissue consisting of asci and paraphyses; cf. thecium, 157.
=Hymenolichens=, lichens of which the fungal constituent is a Hymenomycete, 152-154, 342.
=Hypophloeodal=, thallus growing within the bark, 78, 364.
=Hypothallus=, first growth of hyphae (proto- or pro-thallus) persisting as hyphal growth at base or margin of the thallus, 70, 257 _et passim_.
=Hypothecium=, layer below the thecium (hymenium), 157.
=Intricate cortex=, composed of hyphae densely interwoven but not coalescent, 83.
=Isidium=, coral-like outgrowth on the lichen thallus, 149-151.
=Lecanorine=, apothecium with a thalline margin as in _Lecanora_, 158.
=Lecideine=, apothecium usually dark-coloured or carbonaceous and without a thalline margin, 158.
=Leprose=, mealy or scurfy, like the old form genera, _Lepra_, _Lepraria_, 191.
=Lichen-acids=, organic acids peculiar to lichens, 221 _et seq._
=Lignicolous=, living on wood or trees, 366.
=Lirella=, long narrow apothecium of Graphideae, 158.
=Mazaedium=, fructification of Coniocarpineae, the spores lying as a powdery mass in the capitulum, 176.
=Medulla=, the loose hyphal layer in the interior of the thallus, 88 _et passim_.
=Meristematic=, term applied by Wainio to growing hyphae, 48.
=Microgonidia=, term applied by Minks to minute greenish bodies in lichen hyphae, 26.
=Multi-septate=, term applied to spores with numerous transverse septa, 316 _et seq._
=Murali-divided=, =Muriform=, term applied to spores divided like the masonry of a wall, 187.
=Oidium=, reproductive cell formed by the breaking up of the hyphae, 189.
=Oil-cell=, hyphal cell containing fat globules, 215.
=Orculiform=, see polarilocular.
=Orthidium=, supposed new type of fructification in lichens, 192.
=Palisade-cells=, the terminal cells of the hyphae forming the fastigiate cortex, 82, 83.
=Panniform=, having a felted or matted appearance, 260.
=Paraphysis=, sterile filament in the hymenium, 157.
=Parasymbiosis=, associated harmless but not mutually useful growth of two organisms, 263.
=Parathecium=, hyphal layer round the apothecium, 157.
=Peltate=, term applied to orbicular and horizontal apothecia in the form of a shield, 336.
=Perithecium=, roundish fructification usually with an apical opening (ostiole) containing ascospores, 158 _et passim_.
=Pervious=, referring to scyphi with an opening at the base (_Perviae_), 118.
=Phycolichens=, lichens in which the gonidia are blue-green (Myxophyceae), 52 _et passim_.
=Placodioid=, thallus with a squamulose determinate outline, generally orbicular; cf. effigurate, 80.
=Placodiomorph=, see polarilocular.
=Plectenchyma= (=Plectenchymatous=), pseudoparenchyma of fungi and lichens, 66 _et passim_.
=Pleurogenous=, borne laterally on hyphal cells; see spermatium, 312.
=Pluri-septate=, term applied to spores with several transverse septa, 321 _et seq._
=Podetium=, stalk-like secondary thallus of Cladoniaceae, 114, 293 _et seq._
=Polarilocular=, =Polaribilocular=, two-celled spores with thick median wall traversed by a connecting tube, 188, 340-341.
=Polytomous=, arising of several branches of the podetium from one level, 118.
=Proper margin=, the hyphal margin surrounding the apothecium, 157.
=Prothallus=, =Protothallus=, first stages of hyphal growth; cf. hypothallus, 71.
=Pycnidiospores=, stylospores borne in pycnidia, 198 _et passim_.
=Pycnidium=, roundish fructification, usually with an opening at the apex, containing sporophores and stylospores; cf. spermogonium, 192 _et seq._
=Pyrenolichens=, in which the fructification is a closed perithecium, 173 _et passim_.
=Radiate thallus=, the tissues radiate from a centre, 98 _et seq._
=Rhagadiose=, deeply chinked, 74; cf. rimose.
=Rhizina=, attaching “rootlet,” 92-94.
=Rimose=, =Rimulose=, cleft or chinked into areolae, 73.
=Rimose-diffract=, widely cracked or chinked, 74.
=Scutellate=, shaped like a platter, 156.
=Scyphus=, cup-like dilatation of the podetium, 111, 117.
=Signature=, a term in ancient medicine to signify the resemblance of a plant to any part of the human body, 406, 409.
=Soralium=, group of soredia surrounded by a definite margin, 144.
=Soredium=, minute separable particle arising from the gonidial tissue of the thallus, and consisting of algae and hyphae, 141.
=Spermatium=, spore-like body borne in the spermogonium, regarded as a non-motile male cell or as a pycnidiospore, 201.
=Spermogonium=, roundish closed receptacle containing spermatia, 192.
=Sphaeroid-cell=, swollen hyphal cell, containing fat globules, 215.
=Squamule=, a small thalline lobe or scale, 74 _et passim_.
=Sterigma=, Nylander’s term for the spermatiophore, 197.
=Stratose thallus=, where the tissues are in horizontal layers, 70.
=Stratum=, a layer of tissue in the thallus, 70.
=Symbiont=, one of two dissimilar organisms living together, 32.
=Symbiosis=, a living together of dissimilar organisms, also termed commensalism, 31, 32 _et seq._
=Tegulicolous=, living on tiles, 369.
=Terebrator=, boring apparatus, term used by Lindau for the lichen “trichogyne,” 179.
=Thalline margin=, an apothecial margin formed of and usually coloured like the thallus; cf. amphithecium.
=Thallus=, vegetative body or soma of the lichen plant, 11, 421. Endogenous thallus in which the alga predominates, 68. Exogenous thallus in which the fungus predominates, 69.
=Theca=, enlarged cell containing spores; cf. ascus.
=Thecium=, layer of tissue in the apothecium consisting of asci and paraphyses; cf. hymenium, 157.
=Trichogyne=, prolongation of the egg-cell in Florideae which acts as a receptive tube; septate hypha in lichens arising from the ascogonium, 160, 177-181, 273.
=Woronin’s hypha=, a coiled hypha occurring in the centre of the fruit primordium, 159, 163.
ERRATA
p. 24. _For_ Baranetsky _read_ Baranetzky. p. 277. For _Ascolium_ read _Acolium_. p. 318. For _Lepolichen coccophora_ read _coccophorus_.
Transcriber’s Note: The errata have been corrected.
INTRODUCTION
Lichens are, with few exceptions, perennial aerial plants of somewhat lowly organization. In the form of spreading encrustations, horizontal leafy expansions, of upright strap-shaped fronds or of pendulous filaments, they take possession of the tree-trunks, palings, walls, rocks or even soil that afford them a suitable and stable foothold. The vegetative body, or thallus, which may be extremely long-lived, is of varying colour, white, yellow, brown, grey or black. The great majority of lichens are Ascolichens and reproduction is by ascospores produced in open or closed fruits (apothecia or perithecia) which often differ in colour from the thallus. There are a few Hymenolichens which form basidiospores. Vegetative reproduction by soredia is frequent.
Lichens abound everywhere, from the sea-shore to the tops of high mountains, where indeed the covering of perpetual snow is the only barrier to their advance; but owing to their slow growth and long duration, they are more seriously affected than are the higher plants by chemical or other atmospheric impurities and they are killed out by the smoke of large towns: only a few species are able to persist in somewhat depauperate form in or near the great centres of population or of industry.
The distinguishing feature of lichens is their composite nature: they consist of two distinct and dissimilar organisms, a fungus and an alga, which, in the lichen thallus, are associated in some kind of symbiotic union, each symbiont contributing in varying degree to the common support: it is a more or less unique and not unsuccessful venture in plant-life. The algae—Chlorophyceae or Myxophyceae—that become lichen symbionts or “gonidia” are of simple structure, and, in a free condition, are generally to be found in or near localities that are also the customary habitats of lichens. The fungus is the predominant partner in the alliance as it forms the fruiting bodies. It belongs to the Ascomycetes[1], except in a few tropical lichens (Hymenolichens), in which the fungus is a Basidiomycete. These two types of plants (algae and fungi) belonging severally to many different genera and species have developed in their associated life this new lichen organism, different from themselves as well as from all other plants, not only morphologically but physiologically. Thus there has arisen a distinct class, with families, genera and species, which through all their varying forms retain the characteristics peculiar to lichens.
In the absence of any “visible” seed, there was much speculation in early days as to the genesis of all the lower plants and many opinions were hazarded as to their origin. Luyken[2], for instance, thought that lichens were compounded of air and moisture. Hornschuch[3] traced their origin to a vegetable infusorium, _Monas Lens_, which became transformed to green matter and was further developed by the continued action of light and air, not only to lichens, but to algae and mosses, the type of plant finally evolved being determined by the varying atmospheric influences along with the chemical nature of the substratum. An account[4] is published of Nees von Esenbeck, on a botanical excursion, pointing out to his students the green substance, _Lepraria botryoides_, which covered the lower reaches of walls and rocks, while higher up it assumed the grey lichen hue. This afforded him sufficient proof that the green matter in that dry situation changed to lichens, just as in water it changed to algae. An adverse criticism by Dillenius[5] on a description of a lichen fructification is not inappropriate to those early theorists: “Ex quo apparet, quantum videre possint homines, si imaginatione polleant.”
A constant subject of speculation and of controversy was the origin of the green cells, so dissimilar to the general texture of the thallus. It was thought finally to have been established beyond dispute that they were formed directly from the colourless hyphae and, as a corollary, _Protococcus_ and other algal cells living in the open were considered to be escaped gonidia or, as Wallroth[6] termed them, “unfortunate brood-cells,” his view being that they were the reproductive organs of the lichen plant that had failed to develop.
It was a step forward in the right direction when lichens were regarded as transformed algae, among others by Agardh[7], who believed that he had followed the change from _Nostoc lichenoides_ to the lichen _Collema limosum_. Thenceforward their double resemblance, on the one hand to algae, on the other to fungi, was acknowledged, and influenced strongly the trend of study and investigation.
The announcement[8] by Schwendener[9] of the dual hypothesis solved the problem for most students, though the relation between the two symbionts is still a subject of controversy. The explanation given by Schwendener, and still held by some[10], that lichens were merely fungi parasitic on algae, was indeed a very inadequate conception of the lichen plant, and it was hotly contested by various lichenologists. Lauder Lindsay[11] dismissed the theory as “merely the most recent instance of German transcendentalism applied to the Lichens.” Earlier still, Nylander[12], in a paper dealing with cephalodia and their peculiar gonidia, had denounced it: “Locum sic suum dignum occupat algolichenomachia inter historias ridiculas, quae hodie haud paucae circa lichenes, majore imaginatione quam scientia, enarrantur.” He never changed his attitude and Crombie[13], wholly agreeing with his estimate of these “absurd tales,” translates a much later pronouncement by him[14]: “All these allegations belong to inept Schwendenerism and scarcely deserve even to be reviewed or castigated so puerile are they—the offspring of inexperience and of a light imagination. No true science there.” Crombie[15] himself in a first paper on this subject declared that “the new theory would necessitate their degradation from the position they have so long held as an independent class.” He scornfully rejected the whole subject as “a Romance of Lichenology, or the unnatural union between a captive Algal damsel and a tyrant Fungal master.” The nearest approach to any concession on the algal question occurs in a translation by Crombie[16] of one of Nylander’s papers. It is stated there that a saxicolous alga (_Gongrosira_ Kütz.) had been found bearing the apothecia of _Lecidea herbidula_ n. sp. Nylander adds: “This algological genus is one which readily passes into lichens.” At a later date, Crombie[17] was even more comprehensively contemptuous and wrote: “whether viewed anatomically or biologically, analytically or synthetically, it is instead of being true science, only the Romance of Lichenology.” These views were shared by many continental lichenologists and were indeed, as already stated, justified to a considerable extent: it was impossible to regard such a large and distinctive class of plants as merely fungi parasitic on the lower algae.
Controversy about lichens never dies down, and that view of their parasitic nature has been freshly promulgated among others by the American lichenologist Bruce Fink[18]. The genetic origin of the gonidia has also been restated by Elfving[19]: the various theories and views are discussed fully in the chapter on the lichen plant.
Much of the interest in lichens has centred round their symbiotic growth. No theory of simple parasitism can explain the association of the two plants: if one of the symbionts is withdrawn—either fungus or alga—the lichen as such ceases to exist. Together they form a healthy unit capable of development and change: a basis for progress along new lines. Permanent characters have been formed which are transmitted just as in other units of organic life.
A new view of the association has been advanced by F. and Mme Moreau[20]. They hold that the most characteristic lichen structures—more particularly the cortex—have been induced by the action of the alga on the fungus. The larger part of the thallus might therefore be regarded as equivalent to a gall: “it is a cecidium, an algal cecidium, a generalized biomorphogenesis.”
The morphological characters of lichens are of exceptional interest, conditioned as they are by the interaction of the two symbionts, and new structures have been evolved by the fungus which provides the general tissue system. Lichens are plants of physiological symbiotic origin, and that aspect of their life-history has been steadily kept in view in this work. There are many new requirements which have had to be met by the lichen hyphae, and the differences between them and the true fungal hyphae have been considered, as these are manifested in the internal economy of the compound plant, and in its reaction to external influences such as light, heat, moisture, etc.
The pioneers of botanical science were of necessity occupied almost exclusively with collecting and describing plants. As the number of known lichens gradually accumulated, affinities were recognized and more or less successful efforts were made to tabulate them in classes, orders, etc. It was a marvellous power of observation that enabled the early workers to arrange the first schemes of classification. Increasing knowledge aided by improved microscopes has necessitated changes, but the old fundamental “genus” _Lichen_ is practically equivalent to the Class _Lichenes_.
The study of lichens has been a slow and gradual process, with a continual conflict of opinion as to the meaning of these puzzling plants—their structure, reproduction, manner of subsistence and classification as well as their relation to other plants. It has been found desirable to treat these different subjects from a historical aspect, as only thus can a true understanding be gained, or a true judgment formed as to the present condition of the science. It is the story of the evolution of lichenology as well as of lichens that has yielded so much of interest and importance.
The lichenologist may claim several advantages in the study of his subject: the abundant material almost everywhere to hand in country districts, the ease with which the plants are preserved, and, not least, the interest excited by the changes and variations induced by growth conditions; there are a whole series of problems and puzzles barely touched on as yet that are waiting to be solved.
In field work, it is important to note accurately and carefully the nature of the substratum as well as the locality. Crustaceous species should be gathered if possible along with part of the wood or rock to which they are attached; if they are scraped off, the pieces may be reassembled on gummed paper, but that is less satisfactory. The larger forms are more easily secured; they should be damped and then pressed before being laid away: the process flattens them, but it saves them from the risk of being crushed and broken, as when dry they are somewhat brittle. Moistening with water will largely restore their original form. All parts of the lichen, both thallus and fruit, can be examined with ease at any time as they do not sensibly alter in the herbarium, though they lose to some extent their colouring: the blue-grey forms, for instance, often become a uniform dingy brownish-grey.
Microscopic examination in the determination of species is necessary in many instances, but that disability—if it ranks as such—is shared by other cryptogams, and may possibly be considered an inducement rather than a deterrent to the study of lichens. For temporary examination of microscopic preparations, the normal condition is best observed by mounting them in water. If the plants are old and dry, the addition of a drop or two of potash—or ammonia—solution is often helpful in clearing the membranes of the cells and in restoring the shrivelled spores and paraphyses to their natural forms and dimensions.
If serial microtome sections are desired, more elaborate methods are required. For this purpose Peirce[21] has recommended that “when dealing with plants that are dry but still alive, the material should be thoroughly wetted and kept moist for two days, then killed and fixed in a saturated solution of corrosive sublimate in thirty-five per cent. alcohol.” The solution should be used hot: the usual methods of dehydrating and embedding in paraffin are then employed with extra precautions on account of the extremely brittle nature of lichens.
Another method that also gave good results has been proposed by French[22]: “first the lichen is put into 95 per cent. alcohol for 24 hours, then into thin celloidin and thick celloidin 24 hours each. After this the specimens are embedded in thick celloidin which is hardened in 70 per cent. alcohol for 24 hours and then cut.” French advises staining with borax carmine: it colours the fungal part pale carmine and the algal cells a greenish-red shade.
Modern research methods of work are generally described in full in the publications that are discussed in the following chapters. The student is referred to these original papers for information as to fixing, embedding, staining, etc.
Great use has been made of reagents in determining lichen species. They are extremely helpful and often give the clinching decision when morphological characters are obscure, especially if the plant has been much altered by the environment. It must be borne in mind, however, that a species is a morphological rather than a physiological unit, and it is not the structures but the cell-products that are affected by reagents. Those most commonly in use are saturated solutions of potash and of bleaching-powder (calcium hypochlorite). The former is cited in text-books as KOH or simply as K, the latter as CaCl or C. The C solution deteriorates quickly and must, therefore, be frequently renewed to produce the required reaction, _i.e._ some change of colour. These two reagents are used singly or, if conjointly, K followed by C. The significance of the colour changes has been considered in the discussion on lichen-acids.
Iodine is generally cited in connection with its staining effect on the hymenium of the fruit; the blue colour produced is, however, more general than was at one time supposed and is not peculiar to lichens; the asci of many fungi react similarly though to a less extent. The medullary hyphae in certain species also stain blue with iodine.