CONTENTS XV 



PAGE 



E. Parasitism 260 



a. General statement 



b. Antagonistic symbiosis 



c. Parasymbiosis 



d. Parasymbiosis of fungi 



e. Fungi parasitic on lichens 



/ 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 Phvcolichens . ... 283 



a. Gloeolichens 



b. Ephebaceae and CoUemaceae 



c. Pyrenidiaceae 



d. Heppiaceae and Pannariaceae 



e. Peltigeraceae and Stictaceae 



b2 



