THALLOPHYTES : FUNGI 



79 



plant. In other words, a Lichen is not an individual, but a 

 firm of two individuals very unlike each other. This habit 







9"3^ 



Fig. 70. A common lichen {Physda) growing on bark, showing the spreading thallus 

 and the numerons dark disks (apothecia) bearing the asci. — Caldwell. 



of living together has been called si/mhiosis, and the indi- 

 viduals entering into this relation are called symhioats. 



Fig. 71. A common foliose lichen (Parmdia) growing upon a board, and showing 

 apothecia. — Caldwell. 



