ASCOLICHENES. 



139 



This theory regarding the symbiosis of Fungi and Algse to form a Lichen is 

 termed the Schwendenerian theory, after the first scientist who advanced it with 

 any weight. It had heen already indicated by De Bary, and further arguments 

 in its support have at a later time been adduced by Bornet, Stahl, Treub, 

 Frank, Bonnier, Alfr. Moller and others. 



Fro. 131. Yosfoc Uchenoides, which is attached 

 by a g-erminating thread (M of Collema glaucescens. 



FIG. 133. Epliele pubefccns. 

 The apex of a branch of the 

 thallus with two lateral branches 

 (s) : h its hyphse; g the apical 

 goniclinm of the main branch. 



FIG. 135. A Germinating spore of Physcia parie- 

 tina with Profococcus vivid's. B Synalissa sympliorea 

 with Gl wocapsa. C Cladonia furcata with Proto- 



COt'CUS. 



The thallus of the Lichen appears mainly under three forms : 

 1. The CRUSTACEOUS, which adheres firmly to the substratum 

 (bark, stone) throughout its entire surface, without being raised 

 into any free patches or lobes. It has, in many instances, no- 

 definite outline, and hyphal-branches from it often penetrate 



