FUNGI 



161 



are not single plants, but 

 that each lichen is formed 

 of a fungus and an alga 

 living together so inti- 

 mately as to appear like 

 a single plant. In other 

 words, a lichen is not an 

 individual but a firm of 

 two individuals, very un- 

 like one another. If a 

 lichen be sectioned, the 

 relation between the two 

 constituent plants may be 

 seen (Fig. 156). The fun- 

 gus makes the bulk of the 

 body with its interwoven 



threads, in the p^isV-Cross-section of a lichen, show- 

 meshes Of Which lie the i n K the interwoven mycelium of the 



. . , fungus (m) and the enmeshed alga (g). 



Algae, sometimes scattered, _ Aft er SACHS. 



sometimes massed. It is 



these enmeshed Algae, showing through the transparent my- 



celium, that give the greenish tint to the lichen. 



8 



Fio. 157. Section of one of the cup-like bodies of a lichen, showing the stalk of the 

 cup (m), the masses of Algae (g), and the lining layer of asci (h). After SACHS. 



