X CONTENTS 



2. RADIATE OR SECONDARY THALLUS 



PAGE 



A. Origin of the Podetium 114 



B Structure OF THE Podetium . . . .114 



a. General structure 



b. Gonidial tissue 



c. Cortical tissue 



d. Soredia 



C. Development OF THE ScYPHUS . . • 117 



a. From abortive apothecia 



b. From polytomous branching 



c. From arrested growth 



d. Gonidia of the scyphus 



e. Species without scyphi 



D. Branching OF THE Podetium . . . .119 



E. Perforations and Reticulation of the Pode- 

 tium 120 



F. Rooting Structures OF Cladoniae . . .121 



G. Haptera 122 



H. Morphology of the Podetium . . . 122 



I. PiLOPHORUS AND STEREOCAULON . . . -125 



V. STRUCTURES PECULIAR TO LICHENS 

 I. AERATION STRUCTURES 



A. Cyphellae and Pseudocyphellae . . .126 



a. Historical 



b. Development of cyphellae 



c. Pseudocyphellae 



d. Occurrence and distribution 



B. Breathing-Pores 129 



a. Definite breathing-pores 



b. Other openings in the thajlus 



C. General Aeration OF the Thallus . . .132 



2. cephalodia 



A. Historical and Descriptive . 



B. Classification 



I. cephalodia vera 



II. pseudocephalodia 



C. Algae that form Cephalodia . . .136 



D. Development of Cephalodia . . . .137 



a. Ectotrophic 



b. Endotrophic 



c. Pseudocephalodia 



E. Autosymbiotic Cephalodia 140 



133 



13s 



