THE FUNGI 245 



of the Fungus and its appropriate Alga. This has been 

 observed in the case of our type, and Fig. 100 represents 

 the process. The ascospores of the Physcia have been 

 sown among the cells of the Alga, Cystococcus. The spore 

 on germination sends out a hypha, which at once begins 



FIG. 100. Physcia parietina ; building up of the Lichen out of 

 the Alga and Fungus. A, germinating ascospore (sp) ; the 

 hyphse have seized upon two cells (a, a) of Cystococcus 

 humicola. B, more advanced stage ; sp, sp, ascospores which 

 have produced a web of hyphse, enveloping the Cystococcus 

 cells (a, a} in every direction. Magnified about 400. (After 

 Bonnier.) 



to branch, and its finer ramifications attach themselves 

 closely to the algal cells (Fig. 100, A). As growth 

 proceeds, more and more of the algal colony becomes 

 involved in the web of hyphae arising from the fungal 

 spore, and one after another the Cystococcus cells are 

 seized upon by the suckers of the Fungus (Fig. 100, B). 



