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