Produced by Chris Curnow and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) Cambridge Botanical Handbooks Edited by A. C. SEWARD and A. G. TANSLEY LICHENS CAMBRIDGE UNIVERSITY PRESS C. F. CLAY, MANAGER LONDON: FETTER LANE, E.C.4 [Illustration] LONDON: H. K. LEWIS AND CO., LTD., 136, Gower Street, W.C.1 LONDON: WHELDON & WESLEY, LTD., 28, Essex Street, Strand, W.C.2 NEW YORK: THE MACMILLAN CO. BOMBAY } CALCUTTA } MACMILLAN AND CO., LTD. MADRAS } 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 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 Glossary includes terms used in lichenology, or those with a special lichenological meaning. The Bibliography refers only to works consulted in the preparation of this volume. To save space, etc., the titles of books and papers quoted in the text are generally translated and curtailed: full citations will be found in the Bibliography. Subject-matter has been omitted from the index: references of importance will be found in the Table of Contents or in the Glossary. I would record my thanks to those who have generously helped me during the preparation of the volume: to Lady Muriel Percy for taking notes of spore production, and to Dr Cavers for the loan of reprints. Prof. Potter and Dr Somerville Hastings placed at my disposal their photographs of the living plants. Free use has been made of published text-figures which are duly acknowledged. I have throughout had the inestimable advantage of being able to consult freely the library and herbarium of the British Museum, and have thus been able to verify references to plants as well as to literature. A special debt of gratitude is due to my colleagues Mr Gepp and Mr Ramsbottom for their unfailing assistance and advice. A. L. S. LONDON, _February, 1920_ CONTENTS PAGE GLOSSARY xix ERRATA xxii INTRODUCTION xxiii CHAPTER I HISTORY OF LICHENOLOGY A. INTRODUCTORY 1 B. PERIOD I. PREVIOUS TO 1694 2 C. PERIOD II. 1694-1729 5 D. PERIOD III. 1729-1780 6 E. PERIOD IV. 1780-1803 9 F. PERIOD V. 1803-1846 10 G. PERIOD VI. 1846-1867 15 H. PERIOD VII. 1867 AND AFTER 18 CHAPTER II CONSTITUENTS OF THE LICHEN THALLUS I. LICHEN GONIDIA 1. GONIDIA IN RELATION TO THE THALLUS A. HISTORICAL ACCOUNT OF LICHEN GONIDIA 21 B. GONIDIA CONTRASTED WITH ALGAE 22 C. CULTURE EXPERIMENTS WITH THE LICHEN THALLUS 24 D. THEORIES AS TO THE ORIGIN OF GONIDIA 25 E. MICROGONIDIA 26 F. COMPOSITE NATURE OF THALLUS 27 G. SYNTHETIC CULTURES 27 H. HYMENIAL GONIDIA 30 I. NATURE OF ASSOCIATION BETWEEN ALGA AND FUNGUS 31 _a._ Consortium and symbiosis _b._ Different forms of association J. RECENT VIEWS ON SYMBIOSIS AND PARASITISM 36 2. PHYSIOLOGY OF THE SYMBIONTS A. NUTRITION OF LICHEN ALGAE 39 _a._ Character of algal cells _b._ Supply of nitrogen _c._ Effect on the alga _d._ Supply of carbon _e._ Nutrition within the symbiotic plant _f._ Affinities of lichen gonidia B. NUTRITION OF LICHEN FUNGI 44 C. SYMBIOSIS OF OTHER PLANTS 45 II. LICHEN HYPHAE A. ORIGIN OF HYPHAE 46 B. DEVELOPMENT OF LICHENOID HYPHAE 47 C. CULTURE OF HYPHAE WITHOUT GONIDIA 49 D. CONTINUITY OF PROTOPLASM IN HYPHAL CELLS 51 III. LICHEN ALGAE A. TYPES OF ALGAE 51 _a._ Myxophyceae associated with Phycolichens _b._ Chlorophyceae associated with Archilichens B. CHANGES INDUCED IN THE ALGA 60 _a._ Myxophyceae _b._ Chlorophyceae C. CONSTANCY OF ALGAL CONSTITUENTS 63 D. DISPLACEMENT OF ALGAE WITHIN THE THALLUS 64 _a._ Normal displacement _b._ Local displacement E. NON-GONIDIAL ORGANISMS ASSOCIATED WITH LICHEN HYPHAE 65 F. PARASITISM OF ALGAE ON LICHENS 65 CHAPTER III MORPHOLOGY I. GENERAL ACCOUNT OF LICHEN STRUCTURE ORIGIN OF LICHEN STRUCTURES A. FORMS OF CELL-STRUCTURE 67 B. TYPES OF THALLUS 68 _a._ Endogenous thallus _b._ Exogenous thallus II. STRATOSE THALLUS 1. CRUSTACEOUS LICHENS A. GENERAL STRUCTURE 70 B. SAXICOLOUS LICHENS 70 _a._ Epilithic lichens _aa._ Hypothallus or protothallus _bb._ Formation of crustaceous tissues _cc._ Formation of areolae _b._ Endolithic lichens _c._ Chemical nature of the substratum C. CORTICOLOUS LICHENS 77 _a._ Epiphloeodal lichens _b._ Hypophloeodal lichens 2. SQUAMULOSE LICHENS A. DEVELOPMENT OF THE SQUAMULE 79 B. TISSUES OF SQUAMULOSE THALLUS 81 3. FOLIOSE LICHENS A. DEVELOPMENT OF FOLIOSE THALLUS 82 B. CORTICAL TISSUES 82 _a._ Types of cortical structure _b._ Origin of variation in cortical structure _c._ Loss and renewal of cortex _d._ Cortical hairs C. GONIDIAL TISSUES 87 D. MEDULLA AND LOWER CORTEX 88 _a._ Medulla _b._ Lower cortex _c._ Hypothallic structures E. STRUCTURES FOR PROTECTION AND ATTACHMENT 91 _a._ Cilia _b._ Rhizinae _c._ Haptera F. STRENGTHENING TISSUES OF STRATOSE LICHENS 95 _a._ Produced by development of cortex _b._ Produced by development of veins or nerves III. RADIATE THALLUS 1. CHARACTERS OF RADIATE THALLUS 2. INTERMEDIATE TYPES OF THALLUS 3. FRUTICOSE AND FILAMENTOUS THALLUS A. GENERAL STRUCTURE OF THALLUS 101 Cortical Structures _a._ The fastigiate cortex _b._ The fibrous cortex B. SPECIAL STRENGTHENING STRUCTURES 103 _a._ Sclerotic strands _b._ Chondroid axis C. SURVEY OF MECHANICAL TISSUES 105 D. RETICULATE FRONDS 106 E. ROOTING BASE IN FRUTICOSE LICHENS 108 IV. STRATOSE-RADIATE THALLUS 1. STRATOSE OR PRIMARY THALLUS A. GENERAL CHARACTERISTICS 111 B. TISSUES OF PRIMARY THALLUS 112 _a._ Cortical tissue _b._ Gonidial tissue _c._ Medullary tissue _d._ Soredia 2. RADIATE OR SECONDARY THALLUS A. ORIGIN OF THE PODETIUM 114 B. STRUCTURE OF THE PODETIUM 114 _a._ General structure _b._ Gonidial tissue _c._ Cortical tissue _d._ Soredia C. DEVELOPMENT OF THE SCYPHUS 117 _a._ From abortive apothecia _b._ From polytomous branching _c._ From arrested growth _d._ Gonidia of the scyphus _e._ Species without scyphi D. BRANCHING OF THE PODETIUM 119 E. PERFORATIONS AND RETICULATION OF THE PODETIUM 120 F. ROOTING STRUCTURES OF CLADONIAE 121 G. HAPTERA 122 H. MORPHOLOGY OF THE PODETIUM 122 I. PILOPHORUS AND STEREOCAULON 125 V. STRUCTURES PECULIAR TO LICHENS 1. AERATION STRUCTURES A. CYPHELLAE AND PSEUDOCYPHELLAE 126 _a._ Historical _b._ Development of cyphellae _c._ Pseudocyphellae _d._ Occurrence and distribution B. BREATHING-PORES 129 _a._ Definite breathing-pores _b._ Other openings in the thallus C. GENERAL AERATION OF THE THALLUS 132 2. CEPHALODIA A. HISTORICAL AND DESCRIPTIVE 133 B. CLASSIFICATION 135 I. CEPHALODIA VERA II. PSEUDOCEPHALODIA C. ALGAE THAT FORM CEPHALODIA 136 D. DEVELOPMENT OF CEPHALODIA 137 _a._ Ectotrophic _b._ Endotrophic _c._ Pseudocephalodia E. AUTOSYMBIOTIC CEPHALODIA 140 3. SOREDIA A. STRUCTURE AND ORIGIN OF SOREDIA 141 _a._ Scattered soredia _b._ Isidial soredia _c._ Soredia as buds B. SORALIA 144 _a._ Form and occurrence of soralia _b._ Position of soraliferous lobes _c._ Deep-seated soralia C. DISPERSAL AND GERMINATION OF SOREDIA 147 D. EVOLUTION OF SOREDIA 148 4. ISIDIA A. FORM AND STRUCTURE OF ISIDIA 149 B. ORIGIN AND FUNCTION OF ISIDIA 151 VI. HYMENOLICHENS A. AFFINITY WITH OTHER PLANTS 152 B. STRUCTURE OF THALLUS 153 C. SPORIFEROUS TISSUES 154 CHAPTER IV REPRODUCTION I. REPRODUCTION BY ASCOSPORES A. HISTORICAL SURVEY 155 B. FORMS OF REPRODUCTIVE ORGANS 156 _a._ Apothecia _b._ Perithecia C. DEVELOPMENT OF REPRODUCTIVE ORGANS 159 1. DISCOLICHENS _a._ Carpogonia of gelatinous lichens _b._ Carpogonia of non-gelatinous lichens _c._ General summary _d._ Hypothecium and paraphyses _e._ Variations in apothecial development _aa._ Parmeliae _bb._ Pertusariae _cc._ Graphideae _dd._ Cladoniae 2. PYRENOLICHENS _a._ Development of the perithecium _b._ Formation of carpogonia D. APOGAMOUS REPRODUCTION 174 E. DISCUSSION OF LICHEN REPRODUCTION 177 _a._ The Trichogyne _b._ The Ascogonium F. FINAL STAGES OF APOTHECIAL DEVELOPMENT 181 _a._ Open or closed apothecia _b._ Emergence of ascocarp G. LICHEN ASCI AND SPORES 184 _a._ Historical _b._ Development of the ascus _c._ Development of the spores _d._ Spore germination _e._ Multinucleate spores _f._ Polaribilocular spores II. SECONDARY SPORES A. REPRODUCTION BY OIDIA 189 B. REPRODUCTION BY CONIDIA 190 _a._ Rare instances of conidial formation _b._ Comparison with Hyphomycetes C. CAMPYLIDIUM AND ORTHIDIUM 191 III. SPERMOGONIA OR PYCNIDIA A. HISTORICAL ACCOUNT OF SPERMOGONIA 192 B. SPERMOGONIA AS MALE ORGANS 193 C. OCCURRENCE AND DISTRIBUTION 193 _a._ Relation to thallus and apothecia _b._ Form and size _c._ Colour D. STRUCTURE 196 _a._ Origin and growth _b._ Form and types of spermatiophores _c._ Periphyses and sterile filaments E. SPERMATIA OR PYCNIDIOSPORES 201 _a._ Origin and form _b._ Size and structure _c._ Germination _d._ Variation in pycnidia F. PYCNIDIA WITH MACROSPORES 204 G. GENERAL SURVEY 205 _a._ Sexual or asexual _b._ Comparison with fungi _c._ Influence of symbiosis _d._ Value in diagnosis CHAPTER V PHYSIOLOGY I. CELLS AND CELL PRODUCTS A. CELL-MEMBRANES 209 _a._ Chitin _b._ Lichenin and allied carbohydrates _c._ Cellulose B. CONTENTS AND PRODUCTS OF THE FUNGAL CELLS 213 _a._ Cell-substances _b._ Calcium Oxalate _c._ Importance of calcium oxalate C. OIL-CELLS 215 _a._ Oil-cells of endolithic lichens _b._ Oil-cells of epilithic lichens _c._ Significance of oil-formation D. LICHEN-ACIDS 221 _a._ Historical _b._ Occurrence and examination of acids _c._ Character of acids _d._ Causes of variation in quantity and quality _e._ Distribution of acids E. CHEMICAL GROUPING OF ACIDS 225 I. ACIDS OF THE FAT SERIES II. ACIDS OF THE BENZOLE SERIES SUBSERIES I. ORCINE DERIVATIVES SUBSERIES II. ANTHRACENE DERIVATIVES F. CHEMICAL REAGENTS AS TESTS FOR LICHENS 228 G. CHEMICAL REACTIONS IN NATURE 229 II. GENERAL NUTRITION A. ABSORPTION OF WATER 229 _a._ Gelatinous lichens _b._ Crustaceous lichens _c._ Foliose lichens _d._ Fruticose lichens B. STORAGE OF WATER 232 C. SUPPLY OF INORGANIC FOOD 232 _a._ In foliose and fruticose lichens _b._ In crustaceous lichens D. SUPPLY OF ORGANIC FOOD 235 _a._ From the substratum _b._ From other lichens _c._ From other vegetation III. ASSIMILATION AND RESPIRATION A. INFLUENCE OF TEMPERATURE 238 _a._ High temperature _b._ Low temperature B. INFLUENCE OF MOISTURE 239 _a._ On vital functions _b._ On general development IV. ILLUMINATION OF LICHENS A. EFFECT OF LIGHT ON THE THALLUS 240 _a._ Sun lichens _b._ Colour-changes due to light _c._ Shade lichens _d._ Varying shade conditions B. EFFECT OF LIGHT ON REPRODUCTIVE ORGANS 244 _a._ Position and orientation of fruits with regard to light _b._ Influence of light on colour of fruits V. COLOUR OF LICHENS A. ORIGIN OF LICHEN-COLOURING 245 _a._ Colour given by the algal constituent _b._ Colour due to lichen-acids _c._ Colour due to amorphous substances _d._ Enumeration of amorphous pigments _e._ Colour due to infiltration CHAPTER VI BIONOMICS A. GROWTH AND DURATION OF LICHENS 252 B. SEASON OF FRUIT FORMATION 255 C. DISPERSAL AND INCREASE 256 _a._ Dispersal of crustaceous lichens _b._ Dispersal of foliose lichens _c._ Dispersal of fruticose lichens D. ERRATIC LICHENS 258 E. PARASITISM 260 _a._ General statement _b._ Antagonistic symbiosis _c._ Parasymbiosis _d._ Parasymbiosis of fungi _e._ Fungi parasitic on lichens _f._ Mycetozoa parasitic on lichens F. DISEASES OF LICHENS 268 _a._ Caused by parasitism _b._ Caused by crowding _c._ Caused by adverse conditions G. HARMFUL EFFECT OF LICHENS 269 H. GALL-FORMATION 270 CHAPTER VII PHYLOGENY I. GENERAL STATEMENT A. ORIGIN OF LICHENS 272 B. ALGAL ANCESTORS 273 C. FUNGAL ANCESTORS 273 _a._ Basidiolichens _b._ Ascolichens II. THE REPRODUCTIVE ORGANS A. THEORIES OF DESCENT IN ASCOLICHENS 273 B. RELATION OF LICHENS TO FUNGI 275 _a._ Pyrenocarpineae _b._ Coniocarpineae _c._ Graphidineae _d._ Cyclocarpineae III. THE THALLUS A. GENERAL OUTLINE OF DEVELOPMENT OF THALLUS 281 _a._ Preliminary considerations _b._ Course of evolution in Hymenolichens _c._ Course of evolution in Ascolichens B. COMPARATIVE ANTIQUITY OF ALGAL SYMBIONTS 282 C. EVOLUTION OF PHYCOLICHENS 283 _a._ Gloeolichens _b._ Ephebaceae and Collemaceae _c._ Pyrenidiaceae _d._ Heppiaceae and Pannariaceae _e._ Peltigeraceae and Stictaceae D. EVOLUTION OF ARCHILICHENS 287 _a._ Thallus of Pyrenocarpineae _b._ Thallus of Coniocarpineae _c._ Thallus of Graphidineae _d._ Thallus of Cyclocarpineae _AA._ LECIDEALES _aa._ Coenogoniaceae _bb._ Lecideaceae and Gyrophoraceae _cc._ Cladoniaceae 1. Origin of Cladonia 2. Evolution of the primary thallus 3. Evolution of the secondary thallus 4. Course of podetial development 5. Variation in Cladonia 6. Causes of variation 7. Podetial development and spore-dissemination 8. Pilophorus, Stereocaulon and Argopsis _BB._ LECANORALES _aa._ Course of Development _bb._ Lecanoraceae _cc._ Parmeliaceae _dd._ Usneaceae _ee._ Physciaceae CHAPTER VIII SYSTEMATIC I. CLASSIFICATION A. WORK OF SUCCESSIVE SYSTEMATISTS 304 _a._ Dillenius and Linnaeus _b._ Acharius _c._ Schaerer _d._ Massalongo and Koerber _e._ Nylander _f._ MÃ¼ller-Argau _g._ Reinke _h._ Zahlbruckner B. FAMILIES AND GENERA OF ASCOLICHENS 311 C. HYMENOLICHENS 342 II. NUMBER AND DISTRIBUTION 1. ESTIMATES OF NUMBER 2. GEOGRAPHICAL DISTRIBUTION A. GENERAL SURVEY 343 B. LICHENS OF POLAR REGIONS 345 C. LICHENS OF THE TEMPERATE ZONES 348 D. LICHENS OF TROPICAL REGIONS 352 III. FOSSIL LICHENS CHAPTER IX ECOLOGY A. GENERAL INTRODUCTION 356 B. EXTERNAL INFLUENCES 357 _a._ Temperature _b._ Humidity _c._ Wind _d._ Human Agency C. LICHEN COMMUNITIES 362 1. ARBOREAL 363 _a._ Epiphyllous _b._ Corticolous _c._ Lignicolous 2. TERRICOLOUS 367 _a._ On calcareous soil _b._ On siliceous soil _c._ On bricks _d._ On humus _e._ On peaty soil _f._ On mosses _g._ On fungi 3. SAXICOLOUS 371 _a._ Characters of mineral substrata _b._ Colonization on rocks _c._ Calcicolous _d._ Silicicolous 4. OMNICOLOUS LICHENS 376 5. LOCALIZED COMMUNITIES 378 _a._ Maritime lichens _b._ Sand-dune lichens _c._ Mountain lichens _d._ Tundra lichens _e._ Desert lichens _f._ Aquatic lichens D. LICHENS AS PIONEERS 392 _a._ Soil-formers _b._ Outposts of vegetation 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 âsignaturesâ _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=, Normanâs 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 âmutualism,â 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=, Steinerâs 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=, Steinerâs 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 ârootlet,â 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=, Nylanderâs 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 âtrichogyne,â 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. =Woroninâs 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_. Transcriberâs 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 algaeâChlorophyceae or Myxophyceaeâthat become lichen symbionts or âgonidiaâ 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 âvisibleâ 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: âEx quo apparet, quantum videre possint homines, si imaginatione polleant.â 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, âunfortunate brood-cells,â 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 âmerely the most recent instance of German transcendentalism applied to the Lichens.â Earlier still, Nylander[12], in a paper dealing with cephalodia and their peculiar gonidia, had denounced it: âLocum sic suum dignum occupat algolichenomachia inter historias ridiculas, quae hodie haud paucae circa lichenes, majore imaginatione quam scientia, enarrantur.â He never changed his attitude and Crombie[13], wholly agreeing with his estimate of these âabsurd tales,â translates a much later pronouncement by him[14]: âAll these allegations belong to inept Schwendenerism and scarcely deserve even to be reviewed or castigated so puerile are theyâthe offspring of inexperience and of a light imagination. No true science there.â Crombie[15] himself in a first paper on this subject declared that âthe new theory would necessitate their degradation from the position they have so long held as an independent class.â He scornfully rejected the whole subject as âa Romance of Lichenology, or the unnatural union between a captive Algal damsel and a tyrant Fungal master.â The nearest approach to any concession on the algal question occurs in a translation by Crombie[16] of one of Nylanderâs papers. It is stated there that a saxicolous alga (_Gongrosira_ KÃ¼tz.) had been found bearing the apothecia of _Lecidea herbidula_ n. sp. Nylander adds: âThis algological genus is one which readily passes into lichens.â At a later date, Crombie[17] was even more comprehensively contemptuous and wrote: âwhether viewed anatomically or biologically, analytically or synthetically, it is instead of being true science, only the Romance of Lichenology.â 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 withdrawnâeither fungus or algaâthe 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 structuresâmore particularly the cortexâhave 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: âit is a cecidium, an algal cecidium, a generalized biomorphogenesis.â 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 âgenusâ _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 plantsâtheir 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 disabilityâif it ranks as suchâis 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 potashâor ammoniaâsolution 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 âwhen 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.â 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]: âfirst 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.â 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. CHAPTER I HISTORY OF LICHENOLOGY A. INTRODUCTORY The term âlichenâ 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 âMuscusâ (Moss) by the older writers, and more definitely as âMusco-fungusâ by Morison[23]. In a botanical work published in 1700 by Tournefort[24] all the members of the vegetable kingdom then known were for the first time classified in genera, and the genus _Lichen_ was reserved for the plants that have been so designated since that time, though Dillenius[25] in his works preferred the adjectival name _Lichenoides_. A painstaking historical account of lichens up to the beginning of modern lichenology has been written by Krempelhuber[26], a German lichenologist. He has grouped the data compiled by him into a series of Periods, each one marked by some great advance in knowledge of the subject, though, as we shall see, the advance from period to period has been continuous and gradual. While following generally on the lines laid down by Krempelhuber, it will be possible to cite only the more prominent writers and it will be of much interest to British readers to note especially the work of our own botanists. Krempelhuberâs periods are as follows: I. From the earliest times to the end of the seventeenth century. II. Dating from the arrangement of plants into classes called genera by Tournefort in 1694 to 1729. III. From Micheliâs division of lichens into different orders in 1729 to 1780. IV. The definite and reasoned establishment of lichen genera based on the structure of thallus and fruit by Weber in 1780 to 1803. V. The arrangement of all known lichens under their respective genera by Acharius in 1803 to 1846. VI. The recognition of spore characters in classification by De Notaris in 1846 to 1867. A seventh period which includes modern lichenology, and which dates after the publication of Krempelhuberâs _History_, was ushered in by Schwendenerâs announcement in 1867 of the hypothesis as to the dual nature of the lichen thallus. Schwendenerâs theory gave a new impulse to the study of lichens and strongly influenced all succeeding investigations. 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 same or somewhat similar lichens are also probably alluded to by the Greek physician Dioscorides, in his work on _Materia Medica_, A.D. 68. About the same time Pliny the elder, who was a soldier and traveller as well as a voluminous writer, mentions them in his _Natural History_ which was completed in 77 A.D. During the centuries that followed, there was little study of Natural History, and, in any case, lichens were then and for a long time after considered to be of too little economic value to receive much attention. In the sixteenth century there was a great awakening of scientific interest all over Europe, and, after the printing-press had come into general use, a number of books bearing on Botany were published. It will be necessary to chronicle only those that made distinct contributions to the knowledge of lichens. The study of plants was at first entirely from a medical standpoint and one of the first works, and the first book on Natural History, printed in England, was the _Grete Herball_[27]. It was translated from a French work, _Hortus sanitatis_, and published by Peter Treveris in Southwark. One of the herbs recommended for various ailments is âMuscus arborum,â the tree-moss (_Usnea_). A somewhat crude figure accompanies the text. Ruel[28] of Soissons in France, Dorstenius[29], Camerarius[30] and Tabernaemontanus[31] in Germany followed with works on medical or economic botany and they described, in addition to the tree-moss, several species of reputed value in the art of healing now known as _Sticta_ (_Lobaria_) _pulmonaria_, _Lobaria laetevirens_, _Cladonia pyxidata_, _Evernia prunastri_ and _Cetraria islandica_. Meanwhile LâObel[32], a Fleming, who spent the latter part of his life in England and is said to have had charge of a physic garden at Hackney, was appointed botanist to James I. He published at Antwerp a large series of engravings of plants, and added a species of _Ramalina_ to the growing list of recognized lichens. Dodoens[33], also a Fleming, records not only the _Usnea_ of trees, but a smaller and more slender black form which is easily identifiable as _Alectoria jubata_. He also figures _Lichen pulmonaria_ and gives the recipe for its use. The best-known botanical book published at that time, however, is the _Herball_ of John Gerard[34] of London, Master in Chirurgerie, who had a garden in Holborn. He recommends as medicinally valuable not only _Usnea_, but also _Cladonia pyxidata_, for which he coined the name âcuppe- or chalice-moss.â About the same time Schwenckfeld[35] recorded, among plants discovered by him in Silesia, lichens now familiar as _Alectoria jubata_, _Cladonia rangiferina_ and a species of _Peltigera_. Among the more important botanical writers of the seventeenth century may be cited Colonna[36] and Bauhin[37]. The former, an Italian, contributes, in his _Ecphrasis_, descriptions and figures of three additional species easily recognized as _Physcia ciliaris_, _Xanthoria parietina_ and _Ramalina calicaris_. Kaspar Bauhin, a professor in Basle, who was one of the most advanced of the older botanists, was the first to use a binomial nomenclature for some of his plants. He gives a list in his _Pinax_ of the lichens with which he was acquainted, one of them, _Cladonia fimbriata_, being a new plant. John Parkinsonâs[38] _Herball_ is well known to English students; he adds one new species for England, _Lobaria pulmonaria_, already recorded on the Continent. Parkinson was an apothecary in London and held the office of the Kingâs Herbarist; his garden was situated in Long Acre. Howâs[39] _Phytographia_ is notable as being the first account of British plants compiled without reference to their healing properties. Five of the plants described by him are lichen species: âLichen arborum sive pulmonariaâ (_Lobaria pulmonaria_), âLichen petraeus tinctoriusâ (_Roccella_), âMuscus arboreusâ (_Usnea_), âCorallina montanaâ (_Cladonia rangiferina_) and âMuscus pixoidesâ (_Cladonia_). Several other British species were added by Merrett[40], who records in his Pinax, âMuscus arboreus umbilicatusâ (_Physcia ciliaris_), âMuscus aureus tenuissimusâ (_Teloschistes flavicans_), âMuscus caule rigidoâ (_Alectoria_) and âLichen petraeus purpureusâ (_Parmelia omphalodes_), the last-named, a rock lichen, being used, he tells us, for dyeing in Lancashire. Merret or Merrett was librarian to the Royal College of Physicians. His _Pinax_ was undertaken to replace Howâs _Phytographia_ published sixteen years previously and then already out of print. Merrettâs work was issued in 1666, but the first impression was destroyed in the great fire of London and most of the copies now extant are dated 1667. He arranged the species of plants in alphabetical order, but as the work was not critical it fell into disuse, being superseded by John Rayâs _Catalogus_ and _Synopsis_. To Robert Plot[41] we owe the earliest record of _Cladonia coccifera_ which had hitherto escaped notice; it was described and figured as a new and rare plant in the _Natural History of Staffordshire_[41]. Plot was the first Custos of Ashmoleâs Museum in Oxford and he was also the first to prepare a County Natural History. The greatest advance during this first period was made by Robert Morison[42], a Scotsman from Aberdeen. He studied medicine at Angers in France, superintended the Duke of Orleansâ garden at Blois, and finally, after his return to this country in 1669, became Keeper of the botanic garden at Oxford. In the third volume of his great work[42] on Oxford plants, which was not issued till after his death, the lichens are put in a separate groupââMusco-fungusââand classified with some other plants under âPlantae Heteroclitae.â The publication of the volume projects into the next historical period. Long before this date John Ray had begun to study and publish books on Botany. His _Catalogue of English Plants_[43] is considered to have commenced a new era in the study of the science. The _Catalogue_ was followed by the _History of Plants_[44], and later by a _Synopsis of British Plants_[45], and in all of these books lichens find a place. Two editions of the _Synopsis_ appeared during Rayâs lifetime, and to the second there is added an Appendix contributed by Samuel Doody which is entirely devoted to Cryptogamic plants, including not a few lichensâstill called âMossesââdiscovered for the first time. Doody, himself an apothecary, took charge of the garden of the Apothecariesâ Society at Chelsea, but his chief interest was Cryptogamic Botany, a branch of the subject but little regarded before his day. Pulteney wrote of him as the âDillenius of his time.â Among Doodyâs associates were the Rev. Adam Buddle, James Petiver and William Sherard. Buddle was primarily a collector and his herbarium is incorporated in the Sloane Herbarium at the British Museum. It contains lichens from all parts of the world, many of them contributed by Doody, Sherard and Petiver. Only a few of them bear British localities: several are from Hampstead where Buddle had a church. The Society of Apothecaries had been founded in 1617 and the members acquired land on the river-front at Chelsea, which was extended later and made into a Physick Garden. James Petiver[46] was one of the first Demonstrators of Plants to the Society in connection with the garden, and one of his duties was to conduct the annual herborizing tours of the apprentices in search of plants. He thus collected a large herbarium on the annual excursions, as well as on shorter visits to the more immediate neighbourhood of London. He wrote many tracts on Natural History subjects, and in these some lichens are included. He was one of the best known of Rayâs correspondents, and owing to his connection with the Physic Garden received plants from naturalists in foreign countries. Sherard, another of Doodyâs friends, had studied abroad under Tournefort and was full of enthusiasm for Natural Science. It was he who brought Dillenius to England and finally nominated him for the position of the first Sherardian Professor of Botany at Oxford. Another well-known contemporary botanist was Leonard Plukenet[47] who had a botanical garden at Old Palace Yard, Westminster. He wrote several botanical works in which lichens are included. Morison is the only one of all the botanists of the time who recognized lichens as a group distinct from mosses, algae or liverworts, and even he had very vague ideas as to their development. Malpighi[48] had noted the presence of soredia on the thallus of some species, and regarded them as seeds. Porta[49], a Neapolitan, has been quoted by Krempelhuber as probably the first to discover and place on record the direct growth of lichen fronds from green matter on the trunks of trees. C. PERIOD II. 1694-1729 The second Period is ushered in with the publication of a French work, _Les ÃlÃ©mens de Botanique_ by Tournefort[50], who was one of the greatest botanists of the time. His object wasââto facilitate the knowledge of plants and to disentangle a science which had been neglected because it was found
{'title': 'Lichens by Annie Lorrain Smith', 'source': 'Project Gutenberg', 'lang': 'en'}