viii CONTENTS 



II. LICHEN HYPHAE 



PAGE 



A. ORIGIN OF HYPHAE .46 



B. DEVELOPMENT OF LICHENOID HYPHAE ... 47 



C. CULTURE OF HYPHAE WITHOUT GONIDIA . . 49 



D. CONTINUITY OF PROTOPLASM IN HYPHAL CKLLS . 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 



i. 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 



f>. Endolithic lichens 



c. Chemical nature of the substratum 



C. CORTICOLOUS LICHENS .... -77 



a. Epiphloeodal lichens 



b. Hypophloeodal lichens 



