Mutualism with Continuous Contact 



365 



demonstrated in the laboratory by suitable techniques that permit the 

 algal and fungal components to be cultured separately, as is sug- 

 gested in Fig. 10.1. Many lichens grow abundantly on bare rock 

 surfaces where the lack of moisture and of organic matter would make 

 life impossible for most independent algae and fungi. 



Other equally fascinating instances of niutualistic symbiosis in- 

 volving two plant species are to be found in nature. A well-known 

 example, and one already mentioned as of great ecological importance 

 in relation to nutrients (Chapter 8), is the bacteria of the genus 



Mature lichen 



Ascospores 



Pure cultures 



Fungus 



Clasping hyphae^- 



Association 



Lichen is formed in nature but 

 rarely in laboratory 



Fig. 10.1. Diagram illustrating the symbiotic partnership represented by the 



lichen Cladonia cristatella and its separation in the laboratory into algal and fungal 



components. When the components are recombined in the laboratory, the typical 



morphology of the lichen is not developed, evidently because of the lack of certain 



environmental conditions found in nature. ( Burkholder, 1952, Copyright Baitsell's 



Science in Progress, Yale University Press.) 



