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Lichens

Annie Lorrain Smith

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LICHENS

LICHENS

CAMBRIDGE UNIVERSITY PRESS C. F. CLAY, Manager LONDON: FETTER LANE, E.C.4 LONDON: H. K. LEWIS AND CO., Ltd. , 136, Gower Street, W.C.1 LONDON: WHELDON &amp; WESLEY, Ltd. , 28, Essex Street, Strand, W.C.2 NEW YORK: THE MACMILLAN CO. TORONTO: THE MACMILLAN CO. OF CANADA, Ltd. TOKYO: MARUZEN-KABUSHIKI-KAISHA ALL RIGHTS RESERVED LICHENS BY ANNIE LORRAIN SMITH, F.L.S. ACTING ASSISTANT, BOTANICAL DEPARTMENT, BRITISH MUSEUM CAMBRIDGE: AT THE UNIVERSITY PRESS 1921 PRINTED IN GREAT BRITAIN...

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PREFACE

PREFACE

The publication of this volume has been delayed owing to war conditions, but the delay is the less to be regretted in that it has allowed the inclusion of recent work on the subject. Much of the subject-matter is of common knowledge to lichenologists, but in the co-ordination and arrangement of the facts the original papers are cited throughout. The method has somewhat burdened the pages with citations, but it is hoped that, as a book of reference, its value has been enhanced thereby. The Glossa

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GLOSSARY

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 fi

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ERRATA

ERRATA

Transcriber’s Note: The errata have been corrected....

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INTRODUCTION

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 a

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A. Introductory

A. Introductory

The term “lichen” is a word of Greek origin used by Theophrastus in his History of Plants to signify a superficial growth on the bark of olive-trees. The name was given in the early days of botanical study not to lichens, as we understand them, but to hepatics of the Marchantia type. Lichens themselves were generally described along with various other somewhat similar plants as “Muscus” (Moss) by the older writers, and more definitely as “Musco-fungus” by Morison [23] . In a botanical work publi

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B. Period I. Previous to 1694

B. Period I. Previous to 1694

Our examination of lichen literature takes us back to Theophrastus, the disciple of Plato and Aristotle, who lived from 371 to 284 B.C. , and who wrote a History of Plants , one of the earliest known treatises on Botany. Among the plants described by Theophrastus, there are evidently two lichens, one of which is either an Usnea or an Alectoria , and the other certainly Roccella tinctoria , the last-named an important economic plant likely to be well known for its valuable dyeing properties. The

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C. Period II. 1694-1729

C. Period II. 1694-1729

The second Period is ushered in with the publication of a French work, Les Élémens de Botanique by Tournefort [50] , who was one of the greatest botanists of the time. His object was—“to facilitate the knowledge of plants and to disentangle a science which had been neglected because it was found to be full of confusion and obscurity.” Up to this date all plants were classified or listed as individual species. It was Tournefort who first arranged them in groups which he designated “genera” and he

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D. Period III. 1729-1780

D. Period III. 1729-1780

Lichens were henceforth regarded as a distinct genus or section of plants. Micheli [56] , an Italian botanist, Keeper of the Grand Duke’s Gardens in Florence, realized the desirability of still further delimitation, and he broke up Tournefort’s large comprehensive genera into numerical Orders. In the genus Lichen , he found occasion for 38 of these Orders, determined mainly by the character of the thallus, and the position on it of apothecia and soredia. He enumerates the species, many of them n

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E. Period IV. 1780-1803

E. Period IV. 1780-1803

The inevitable next advance was made by Weber [72] who at the time was a Professor at Kiel. In a first work dealing with lichens he had followed Linnaeus; then he published a new method of classification in which the lichens are considered as an independent Order of Cryptogamia, and that Order, called “Aspidoferae,” he subdivided into genera. His ideas had been partly anticipated by Hill and by Adanson, but the work of Weber indicates a more correct view of the nature of lichens. He established

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F. Period V. 1803-1846

F. Period V. 1803-1846

The fine constructive work of Acharius appropriately begins a new era in the history of lichenology. Previous writers had indeed included lichens in their survey of plants, but always as a somewhat side issue. Acharius made them a subject of special study, and by his scientific system of classification raised them to the rank of the other great classes of plants. Acharius was a country doctor at Wadstena on Lake Mälar in Sweden, as he himself calls it, “the country of lichens.” He was attracted

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G. Period VI. 1846-1867

G. Period VI. 1846-1867

The last work of importance, in which microscopic characters were ignored, was the Enumeratio critica Lichenum Europaeum by Schaerer [122] , a veteran lichenologist, who rather sadly realized at the end the limitations of that work, as he asks the reader to accept it “such as it is.” Many years previously, Eschweiler [123] in his Systema and Fée [124] in his account of Cryptogams on Officinal Bark , had given particular attention to the internal structure as well as to the outward form of the li

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H. Period VII. 1867 and after

H. Period VII. 1867 and after

Modern lichenology begins with the enunciation of Schwendener’s [146] theory of the composite nature of the lichen plant. The puzzling resemblance of certain forms to algae, of others to fungi, had excited the interest of botanists from a very early date, and the similarity between the green cells in the thallus, and certain lower forms of algae had been again and again pointed out. Increasing observation concerning the life-histories of these algae and of the gonidia had eventually piled up so

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I. LICHEN GONIDIA

I. LICHEN GONIDIA

Fig. 1. Physcia aipolia Nyl. Vertical section of thallus. a , cortex; b , algal layer; c , medulla; d , lower cortex. × 100 (partly diagrammatic). The thallus or vegetative body of lichens differs from that of other green plants in the sharp distinction both of form and colour between the assimilative cells and the colourless tissues, and in the relative positions these occupy within the thallus: in the greater number of lichen species the green chlorophyll cells are confined to a narrow zone or

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II. LICHEN HYPHAE

II. LICHEN HYPHAE

Lichen hyphae form the ground tissue of the thallus apart from the gonidia or algal cells. They are septate branched filaments of single cell rows and are colourless or may be tinged by pigments or lichen acids to some shade of yellow, brown or black. They are of fungal nature, and are produced by the mature lichen spore. The germination of the spore was probably first observed by Meyer [263] . His account of the actual process is somewhat vague, and he misinterpreted the subsequent development

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III. LICHEN ALGAE

III. LICHEN ALGAE

The algal constituents of the lichen thallus belong to the two classes, Myxophyceae, generally termed blue-green algae, and Chlorophyceae which are coloured bright-green or yellow-green. Most of them are land forms, and, in a free condition, they inhabit moist or shady situations, tree-trunks, walls, etc. They multiply by division or by sporulation within the thallus; zoospores are never formed except in open cultivation. The determination of the genera and species to which the lichen algae seve

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GENERAL ACCOUNT OF LICHEN STRUCTURE

GENERAL ACCOUNT OF LICHEN STRUCTURE

The two organisms, fungus and alga, that enter into the composition of the lichen plant are each characterized by the simplicity of their original structure in which there is little or no differentiation into tissues. The gonidia-forming algae are many of them unicellular, and increase mainly by division or by sporulation into daughter-cells which become rounded off and repeat the life of the mother-cell; others, belonging to different genera, are filaments, mostly of single cell-rows, with apic

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II. STRATOSE THALLUS

II. STRATOSE THALLUS

In the series “Stratosae,” the plant is dorsiventral, the tissues forming the thallus being arranged more or less regularly in strata one above the other ( Fig. 37 ). On the upper surface there is a hyphal layer constituting a cortex, either rudimentary or highly elaborated; beneath the cortex is situated the gonidial zone composed of algae and hyphae in close association; and deeper down the medulla, generally a loose tissue of branching hyphae. The lower cortex which abuts on the medulla may b

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III. RADIATE THALLUS

III. RADIATE THALLUS

In the stratose dorsiventral thallus, there is a widely extended growing area situated round the free margins of the thallus. In the radiate thallus of the fruticose or filamentous lichens, growth is confined to an apical region. Attachment to the substratum is at one point only—the base of the plant—thus securing the exposure of all sides equally to light. The cortex surrounds the fronds, and the gonidia (mostly Protococcaceae) lie in a zone or in groups between the cortex and the medulla. It i

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IV. STRATOSE-RADIATE THALLUS

IV. STRATOSE-RADIATE THALLUS

Fig. 66. Cladonia pyxidata Hoffm. Basal squamule and podetium. a , apothecia; s , spermogonia (after Krabbe). This series includes the lichens of one family only, the Cladoniaceae, the genera of which are characterized by the twofold thallus, one portion being primary, horizontal and stratose, the other secondary and radiate, the latter an upright simple or branching structure termed a “podetium” which narrows above, or widens to form a trumpet-shaped cup or “scyphus” ( Fig. 66 ). The apothecia

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V. STRUCTURES PECULIAR TO LICHENS

V. STRUCTURES PECULIAR TO LICHENS

The thallus of Stictaceae has been regarded by Nylander [424] and others as one of the most highly organized, not only on account of the size attained by the spreading lobes, but also because in that family are chiefly found those very definite cup-like structures which were named “cyphellae” by Acharius [425] . They are small hollow depressions about 1/2 mm. or more in width scattered irregularly over the under surface of the thallus. a. Historical. Cyphellae were first pointed out by the Swiss

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VI. HYMENOLICHENS

VI. HYMENOLICHENS

Lichens in which the fungal elements belong to the Hymenomycetes are confined to three tropical genera. They are associated with blue-green algae and are most nearly related to the Thelephoraceae among fungi. The spores are borne, as in that family, on basidia. Fig. 86. Cora Pavonia Fr. (after Mattirolo). The best known Hymenolichen, Cora Pavonia ( Fig. 86 ), was discovered by Swartz [516] during his travels in the W. Indies (1785-87) growing on trees in the mountains of Jamaica, and the new pla

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1. REPRODUCTION BY ASCOSPORES

1. REPRODUCTION BY ASCOSPORES

The earliest observations as to the propagation of lichens were made by Malpighi [525] who recorded the presence of soredia on the lichen plant and noted their function as reproductive bodies. He was followed after a considerable interval by Tournefort [526] who placed lichens in a class apart owing to the form of the fruit: “This fruit,” he writes, “is a species of bason or cup which seems to take the place of seeds in these kinds of plants.” He figures Ramalina fraxinea and Physcia ciliaris ,

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II. SECONDARY SPORES

II. SECONDARY SPORES

In certain conditions of nutrition, fungal hyphae break up into separate cells, each of which functions as a reproductive conidium or oidium , which on germination forms new hyphae. Neubner [690] has demonstrated a similar process in the hyphae of the Caliciaceae and compares it with the oidial formation described by Brefeld [691] in the Basidiomycetes. The thallus of this family of lichens is granular or furfuraceous; it never goes beyond the Lepra stage of development [692] . In some species i

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III. SPERMOGONIA OR PYCNIDIA

III. SPERMOGONIA OR PYCNIDIA

The name spermogonium was given by Tulasne [700] to the “punctiform conceptacles” that are so plentifully produced on many lichen thalli, on the assumption that they were the male organs of the plant, and that the spore-like bodies borne in them were non-motile male cells or spermatia. The first record of their association with lichens was made by Dillenius [701] , who indicates the presence of black tubercles on the thallus of Physcia ciliaris . He figures them also on several species of Cladon

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I. CELLS AND CELL PRODUCTS

I. CELLS AND CELL PRODUCTS

Any study of cells or cell-membranes in lichens should naturally include those of both symbionts, but the algae though modified have not been profoundly changed, and their response to the influences of the symbiotic environment has been already described in the discussion of lichen gonidia. The description of cells and their contents refers therefore mainly to the fungal tissues which form the framework of the plant; they have been transformed by symbiosis to lichenoid hyphae in some respects di

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II. GENERAL NUTRITION

II. GENERAL NUTRITION

Lichens are capable of enduring almost complete desiccation, but though they can exist with little injury through long periods of drought, water is essential to active metabolism. They possess no special organs for water conduction, but absorb moisture over their whole surface. Several interdependent factors must therefore be taken into account in considering the question of absorption: the type of thallus, whether gelatinous or non-gelatinous, crustaceous, foliose or fruticose, as also the natu

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III. ASSIMILATION AND RESPIRATION

III. ASSIMILATION AND RESPIRATION

a. High Temperature. It has been proved that plants without chlorophyll are less affected by great heat than those that contain chlorophyll. Lichens in which both types are present are more capable of enduring high temperatures than the higher plants, but with undue heat the alga succumbs first. In consequence, respiration, by the fungus alone, can go on after assimilation (photosynthesis) and respiration in the alga have ceased. Most Phanerogams cease assimilation and respiration after being su

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IV. ILLUMINATION OF LICHENS

IV. ILLUMINATION OF LICHENS

As fungi possess no chlorophyll, their vegetative body has little or no use for light and often develops in partial or total darkness. In lichens the alga requires more or less direct illumination; the lichen fungus, therefore, in response to that requirement has come out into the open: it is an adaptation to the symbiotic life, though some lichens, such as those immersed in the substratum, grow with very little light. Like other plants they are sensitive to changes of illumination: some species

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V. COLOUR OF LICHENS

V. COLOUR OF LICHENS

The thalli of many lichens, more especially of those associated with blue-green gonidia, are hygroscopic, and it frequently happens that any addition of moisture affects the colour by causing the gelatinous cell-walls to swell, thus rendering the tissues more transparent and the green colour of the gonidia more evident. As a general rule it is the dry state of the plant that is referred to in any discussion of colour. In the large majority of species the colouring is of a subdued tone—soft bluis

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A. Growth and Duration

A. Growth and Duration

Lichens are perennial plants mostly of slow growth and of long continuance; there can therefore only be approximate calculations either as to their rate of increase in dimensions or as to their duration in time. A series of somewhat disconnected observations have however been made that bear directly on the question, and they are of considerable interest. Meyer [896] was among the first to be attracted by this aspect of lichen life, and after long study he came to the conclusion that growth varie

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B. Season of Fruit Formation

B. Season of Fruit Formation

The presence of apothecia (or perithecia) in lichens does not always imply the presence of spores. In many instances they are barren, the spores having been scattered or not yet matured; the disc in these cases is composed of paraphyses only, with possible traces of asci. In any month of the year, however, some lichens may be found in fruit. Baur [914] found, for instance, that Parmelia acetabulum developed carpogonia the whole year round, though somewhat more abundantly in spring and autumn. Pe

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C. Dispersal and Increase

C. Dispersal and Increase

The natural increase of lichen plants may primarily be sought for in the dispersal of the spores produced in the fruiting-bodies. These are ejected, as in fungi, by the pressure of the paraphyses on the mature ascus. The spores are then carried away by wind, water, insects, etc. In a few lichens gonidia are enclosed in the hymenium and are ejected along with the spores, but, in most, the necessary encounter with the alga is as fortuitous, and generally as certain, as the pollination of anemophil

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D. Erratic Lichens

D. Erratic Lichens

In certain lichens, there is a tendency for the thallus to develop excrescences of nodular form which easily become free and drift about in the wind while still living and growing. They are carried sometimes very long distances, and fall in thick deposits over localities far from their place of origin. The most famous instance is the “manna lichen,” Lecanora esculenta , which has been scientifically examined and described by Elenkin [921] . He distinguishes seven different forms of the species:

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E. Parasitism

E. Parasitism

a. General Statement. The parasitism of Strigula complanata , an exotic lichen found on the leaves of evergreen trees, has been already described [927] ; Dufrenoy [928] records an instance of hyphae from a Parmelia thallus piercing pine-needles through the stomata and causing considerable injury. Lichen hyphae have attacked and destroyed the protonemata of mosses. Cases have also been recorded of Usnea and Ramalina penetrating to the living tissue of the tree on which they grew, and there may be

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F. Diseases of Lichens

F. Diseases of Lichens

a. Caused by Parasitism. Zopf [964] has stated that of all plants, lichens are the most subject to disease, reckoning as diseases all the instances of parasitism by fungi or by other lichens. There are however only rare instances in which total destruction or indeed any permanent harm to the host is the result of such parasitism. At worst the trouble is localized and does not affect the organism as a whole. Some of these cases have been already noted under antagonistic symbiosis or parasymbiosis

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G. Harmful Effect of Lichens

G. Harmful Effect of Lichens

One lichen only, Strigula complanata , a tropical species, has been proved to be truly and constantly parasitic. It grows on the surface of thick leathery leaves such as those of Camellia [967] , etc. and the alga and fungus both penetrate the epidermis and burrow beneath the cuticle and outer cells, causing them to become brown. It undoubtedly injures the leaves. Friedrich [968] has given an isolated instance of the hold-fast hyphae of Usnea piercing through the cortex to the living tissue of t

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H. Gall-Formation

H. Gall-Formation

Several instances of gall-formation to a limited extent have been already noted as caused by parasitic fungi or lichens. Greater abnormality of development is induced in a few species by the presence of minute animals, mites, wood-lice, etc. Zopf [977] noted these deformations of the thallus in specimens of Ramalina Kullensis collected on the coasts of Sweden. The fronds were frequently swollen in a sausage-like manner, and branching was hindered or altogether prevented; apothecia were rarely fo

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I. GENERAL STATEMENT

I. GENERAL STATEMENT

Though lichens are very old members of the vegetable kingdom, as symbiotic plants they yet date necessarily from a time subsequent to the evolution of their component symbionts. Phylogeny of lichens begins with symbiosis. The algae, which belong to those families of Chlorophyceae and Myxophyceae that live on dry land, had become aerial before their association with fungi to form lichens. They must have been as fully developed then as now, since it is possible to refer them to the genus or someti

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II. THE REPRODUCTIVE ORGANS

II. THE REPRODUCTIVE ORGANS

It has been suggested that ascomycetous fungi, from which Ascolichens are directly derived, are allied to the Florideae, owing to the appearance of a trichogyne in the carpogonium of both groups. That organ in the red seaweeds is a long delicate cell in direct communication with the egg-cell of the carpogonium. It is a structure adapted to totally submerged conditions, and fitted to attach the floating spermatia. In fungi there is also a structure considered as a trichogyne [981] , which, in the

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III. THE THALLUS

III. THE THALLUS

a. Preliminary Considerations. The evolution of lichens, as such, has reference mainly to the thallus. Certain developments of the fructification are evident, but the changes in the reproductive organs have not kept pace with those of the vegetative structures: the highest type of fruit, for instance, the apothecium with a thalline margin, occurs in genera and species with a very primitive vegetative structure as well as in those that have attained higher development. Lichens are polyphyletic as

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I. CLASSIFICATION

I. CLASSIFICATION

Since the time when lichens were first recognized as a separate class—as members of the genus Lichen by Tournefort [1016] or as “Musco-fungi” by Morison [1017] ,—many schemes of classification have been outlined, and the history of the science of lichenology, as we have seen, is a record of attempts to understand their puzzling structure, and to express that understanding by relating them to each other and to allied classes of plants. The great diversity of opinion in regard to their affinities

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II. NUMBER AND DISTRIBUTION OF LICHENS

II. NUMBER AND DISTRIBUTION OF LICHENS

Calculations have been made and published, once and again, as to the number of lichen species occurring over the globe or in definite areas. In 1898 Fünfstück stated that about 20,000 different species had been described, but as many of them had been proved to be synonyms, and since many must rank as forms or varieties, the number of well-authenticated species did not then, according to his estimate, exceed 4000. Many additional genera and species have, however, been discovered since then. In En

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III. FOSSIL LICHENS

III. FOSSIL LICHENS

In pronouncing on the great antiquity of lichens, proof has been adduced from physiological rather than from phytogeological evidence. It would have been of surpassing interest to trace back these plants through the ages, even if it were never possible to assign to any definite period the first symbiosis of the fungus and alga; but among fossil plants there are only scanty records of lichens and even these few are of doubtful determination. The reason for this is fairly obvious: not only are the

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A. General Introduction

A. General Introduction

Ecology is the science that deals with the habitats of plants and their response to the environment of climate or of substratum. Ecology in the lichen kingdom is habitat “writ large,” and though it will not be possible in so wide a field to enter into much detail, even a short examination of lichens in this aspect should yield interesting results, especially as lichens have never, at any time, been described without reference to their habitat. In very early days, medicinal Usneas were supposed t

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B. External Influences

B. External Influences

The climatic factors most favourable to lichen development are direct light (already discussed) [1119] , a moderate or cold temperature, constant moisture and a clear pure atmosphere. Wind also affects their growth. a. Temperature. Lichens, as we have seen, can endure the heat of direct sunlight owing to the protection afforded by thickened cortices, colour pigments, etc. Where such heat is so intense as to be injurious the gonidia succumb first [1120] . Lichens endure low temperatures better th

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C. Lichen Communities

C. Lichen Communities

Lichen communities fall into a few definite groups, though, as we shall see, not a few species may be found to occur in several groups—species that have been designated by some workers as “wanderers.” The leading communities are: 1. Arboreal , including those that grow on leaves, bark or wood. 2. Terricolous , ground-lichens. 3. Saxicolous , rock-lichens. 4. Omnicolous , lichens that can exist on the most varied substrata, such as bones, leather, iron, etc. 5. Localized Communities in which owin

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D. Lichens As Pioneers

D. Lichens As Pioneers

a. Soil-formers. The part played by lichens in the “Economy of Nature” is of very real importance: to them is allotted the pioneer work of breaking down the hard rock surfaces and preparing a soil on which more highly developed plants can grow. This was pointed out by Linnaeus [1218] who thus describes the succession of plants: “Crustaceous lichens,” he writes, “are the first foundation of vegetation. Though hitherto we have considered theirs a trifling place among plants, nevertheless they are

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A. Lichens as Food.

A. Lichens as Food.

a. Food for Insects, etc. Some of the earlier botanists made careful observations on the important place occupied by lichens in nature as affording food to many small animals. In 1791 Jacques Brez [1226] wrote his Flore des Insectophyles , and in the list of food-plants he includes seven species of lichens. The “insects” that frequented these lichens were species of the genera Acarus (mites) and Phalena (moths). A few years later Persoon [1227] noted that lichens formed the main food supply of m

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B. Lichens as Medicine

B. Lichens as Medicine

a. Ancient Remedies. An interesting note has been published by Müller-Argau [1266] which seems to trace back the medicinal use of lichens to a very remote age. He tells us that Dr Schweinfurth, the distinguished traveller, who made a journey through the valley of the Nile in 1864, sent to him from Cairo a piece of lichen thallus found in a vase along with berries of Juniperus excelsa and of Sapindus , with some other undetermined seeds. The vase dated from the 18th Dynasty (1700 to 1600 B.C. ),

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C. Lichens as Poisons

C. Lichens as Poisons

Though the acid substances of lichens are most of them extremely irritating when taken internally, very few lichens are poisonous. Keegan [1284] writing on this subject considers this quality of comparative innocuousness as a distinctive difference between fungi and lichens and he decides that it proves the latter to be higher organisms from a physiological point of view: “the colouring matters being true products of deassimilation, whereas those of fungi are decomposition or degradation waste p

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D. Lichens used in Tanning, Brewing and Distilling

D. Lichens used in Tanning, Brewing and Distilling

The astringent property in Cetraria islandica and in Lobaria pulmonaria has been made use of in tanning leather. The latter lichen grows commonly on oak and could hardly be gathered in sufficient quantity to be of commercial importance. Like many other lichens it develops very slowly. Lobaria pulmonaria has also been used to replace hops in the brewing of beer. Gmelin [1289] in his journey through Siberia visited a monastery at Ussolka where the monks employed it for this purpose. The beer taste

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E. Dyeing Properties of Lichens

E. Dyeing Properties of Lichens

a. Lichens as Dye-plants. Knowledge as to the dyeing properties of lichens dates back to a remote antiquity. It has been generally accepted that lichen-colours are indicated by the prophet Ezekiel in his denunciation of Tyre: “blue and purple from the Isles of Elishah was that which covered thee.” Theophrastus describes certain plants as growing in Crete, and being used to dye wool, etc., and Pliny in his Phycos Thalassion is also understood as referring to the lichen Roccella , “with crisp leav

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F. Lichens in Perfumery

F. Lichens in Perfumery

a. Lichens as Perfumes. There are a few lichens that find a place in Gerard’s [1315] Herball and that are praised by him as being serviceable to man. Among others he writes of a “Moss that partakes of the bark of which it is engendered. It is to be used in compositions which serve for sweet perfumes and that take away wearisomeness.” At a much later date we find Amoreux [1316] recording the fact that Lichen ( Evernia ) prunastri , known as “Mousse de Chêne,” was used as a perfume plant. Though l

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G. Some minor Uses of Lichens

G. Some minor Uses of Lichens

The possibility of extracting gum or mucilage from lichens was demonstrated by the Russian scientist, Professor Georgi [1321] , and later by Amoreux [1322] , the method employed being successive boiling of the plants. The larger foliose or fruticose forms were specially recommended. At a later date, during the Napoleonic wars, the “ingenious Lord Dundonald [1323] ,” of great fame as an inventor, published an account of the extraction process and of the application of the gum to calico-printing,

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APPENDIX POSTSCRIPT TO CHAPTER VII[1325]

APPENDIX POSTSCRIPT TO CHAPTER VII[1325]

In a remarkable paper on The Symbiosis of Lichens [1326] , Dr A. Henry Church has presented a new and striking view of the origin and development of lichens: he has sought to link them up with other classes of vegetation that, in the great transmigration, passed from sea to land. As we know from his Thalassiophyta [1327] and the subaerial transmigration , he holds that primeval algae of advanced form and structure were left exposed on dry land by the gradually receding waters, and those that suc

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ADDENDUM Footnote to Page 404

ADDENDUM Footnote to Page 404

E. M. Holmes [1332] has published recently an account of a substance which seems in some respects to answer to the description of manna (Exodus xvi.; Numbers xi.) more nearly than the generally accepted Lecanora esculenta . The information is quoted from Swann’s book: Fighting the slave-hunters in Central Africa . The author writes (p. 116): “I was shown a curious white substance similar to porridge. It was found early in the morning before the sun rose. On examination it was found to possess al

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