SIMPLE LIFE 



145 



hoof or bracket 



cushions 



Figure 8.16 Mushroom types, about notural size for some members of eoch type, but many 

 species get mucfi larger tfion those shown. 



Jioccosum, provide an example of the form-species in 

 its form-genus. Because imperfect fungi laci< perfect 

 stages, they often cannot be adequately separated 

 from one another, hence may be diagnosed on the 

 basis of diseases they cause. 



LICHENS 



Lichens are of ecological importance because they 

 usually represent the first living things to grow upon 

 rocks. Although lichens represent combinations of 

 algae and fungi, not all algae and fungi form lichens. 

 The only true algae found in lichens are the Chloro- 

 phyta; however, the blue-green algae (Cyanophyta) 

 also form lichens. Therefore, "algae" in the present 

 discussion will include the moneran Phylum Cyano- 

 phyta as well as the plant Phylum Chlorophyta. 



The known lichen-forming fungi are found only in 

 the Ascomycetes and Basidiomycetes. As far as is 

 known, these particular fungi are strictly lichen- 

 forming, hence are completely dependent upon the 

 lichen association for their food and always benefit 

 from the relationship. In some cases at least, 

 lichen-forming fungi supply necessary moisture and, 

 perhaps, growth-stimulating substances to the algae, 

 which are trapped and included within a lichen. 

 However, whether or not algae benefit from being as- 

 sociated with fungi, the relationship is essentially 

 one of algal enslavement, a free-living alga being 

 "entrapped" by a fungus. 



All lichens once were accepted as examples of 

 mutualism, the assumption being that both the alga 

 and fungus always benefited from the association. 

 However, there is reason to doubt that such is always 



