218 



CLASS ASCOMYCETEAE 





Fig. 72. Morphologic types of lichens. (A) Crustose type, Lecidea platycarpa Ach. 

 (B) Foliose type, Gyrophora muhlenbergii Ach. (C) Fruticose type, Stereocaulon 

 coralloides E. Fr., fruticose podetium ("secondary thallus"). (D) Pendent type, 

 Usnea harbata (L.) Wigg., portion of thallus with apothecia. (A, after Reinke: Jahrb. 

 ^c^ss. Botan., 28:70-150. B-D, after Schneider: A Text-book of General Lichenology, 

 Binghamton, N.Y., Willard N. Clute & Co.) 



Amphiloma growing in colonies of mosses (Musci) are capable of destroy- 

 ing the latter by direct parasitic attack. Rock-inhabiting lichens often 

 penetrate the rock itself for some distance by means of their holdfast 

 hyphae. Miss Mellor (1922) called attention to serious damage done to 

 glass windows in some old churches in France where lichens attached 

 themselves to the glass and gradually corroded it. Probably the requisite 

 mineral nutrients of the lichen and enclosed algae are obtained by the 

 hyphae that attach the lichen to its substratum. A very few species of 

 lichens develop in aquatic habitats. 



A great many organic acids, the so-called lichen acids, have been 

 found in the lichens. They were given intensive study by Zopf (1907). 

 Following a suggestion of his, one of his students, F. Tobler (1909) con- 

 ducted experiments which demonstrated that this production of lichen 



