50 



FUNGI 



LICHENS 



Habitat. Lichens grow on rocks, on tree trunks, and on 

 the ground. 



Morphology. In Cetraria the plant body is thallus-like 

 and greatly branched and it lies flat upon the soil. Other 



FIG. 18. Lichen. Iceland moss (Cetraria icelandicd) showing the thallus 

 with hairs along the margins and the reproductive bodies which are the 

 lighter regions of the terminal branches. 



forms are stem-like, branched, and erect, still others are very 

 long, grass-like, and pendulous from trees. It is necessary 

 to section a lichen in order to know its structure and true 

 nature. Sections reveal the fact that a lichen is a composite 

 body made up of a fungus belonging to the ascomycetes and 

 numerous green alga?. This relationship cannot be harmful 

 because these plants occur in great numbers and under con- 



