146 



COMPENDIUM OF GENERAL BOTANY. 



REINKE, and others, some before and some after Scliwendener. 

 Lichens predominate in the colder climates, where they frequently 

 cover large areas of soil ; in our zone they occur on trees, rocks, 

 etc., in the form of crustaceous, foliaceous, or fruticose growths. 

 The chlorophyll -bearing algae (" gonidia ") perforni the assimilat- 

 ing function of this consortium, while the fungus, which usually 

 constitutes the greater bulk of the lichen-body, serves to take 

 up water and watery solutions and to form the attachment to the 

 substratum (by means of rhizoids), and has also the function of 

 sexual reproduction. 1 REES and STAHL have observed the develop- 

 ment of the thallus of a lichen by the artificial synthesis of an alga 



FIG. S7.Cladoma cornucopioides. 

 (After Berthold and Landois.) 



FIG. 86. Sticta fuliginosa. 



(X500.) (After Sachs.) 



FIG. 88. Parmelia parietma. 



(After Krass and Landois.) 



and a fungus. Fig. 86 shows the anatomical structure of the 

 thallus of a foliaceous lichen as seen in cross-section : <?, upper 

 cortical layer ; u, lower cortical layer ; ?*, rhizoids ; m, medullary 

 layer ; ^, algal layer (gonidial). 



Again and again a tendency manifests itself among certain in- 

 vestigators to point out ' ' unsuitable ' ' conditions and relations in 



1 Lichen-spores are very probably not sexual products. STAHL'S observations 

 on Gollema microphyllum have not yet been verified. TRANS. 



