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
A. ABSORPTION OF WATER 229 _a._ Gelatinous lichens _b._ Crustaceous lichens _c._ Foliose lichens _d._ Fruticose lichens
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
A. INFLUENCE OF TEMPERATURE 238 _a._ High temperature _b._ Low temperature
B. INFLUENCE OF MOISTURE 239 _a._ On vital functions _b._ On general development
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
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
C. DISPERSAL AND INCREASE 256 _a._ Dispersal of crustaceous lichens _b._ Dispersal of foliose lichens _c._ Dispersal of fruticose lichens
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
C. FUNGAL ANCESTORS 273 _a._ Basidiolichens _b._ Ascolichens
A. THEORIES OF DESCENT IN ASCOLICHENS 273
B. RELATION OF LICHENS TO FUNGI 275 _a._ Pyrenocarpineae _b._ Coniocarpineae _c._ Graphidineae _d._ Cyclocarpineae
A. GENERAL OUTLINE OF DEVELOPMENT OF THALLUS 281 _a._ Preliminary considerations _b._ Course of evolution in Hymenolichens _c._ Course of evolution in Ascolichens