| 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 |
| 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 |
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