THE LICHENS 



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partner in the Lichen is dominant. We may express the opposition in 

 parallel columns : — 



Fungi 



Best developed in warm countries. 

 Mostly of delicate texture. 

 Prefer shade. 

 Demand much moisture. 

 Thrive in vitiated air. 

 Grow rapidly. 

 Predominantly uncoloured. 

 Develop secondarily. 



Lichens 



Best developed in cold climates. 



Generally of very tough texture. 



Prefer sun. 



Can withstand great drought. 



Demand pure air. 



Grow very slowly. 



Highly pigmented. 



Usually pioneers. 



Lastly we may mention that Lichens have sometimes been used as food. 

 The Iceland Moss, Cetraria islandica, is the best-known case. Boiled with 

 twenty times its bulk of water it yields a stiff jelly which is about 37 per cent, 

 digestible. Du Chaillu records that in the famine of 1867 this became one 

 of the staple foods of the Scandinavian peasants. A leathery Umbilicaria, 

 known as " Rock Tripe," has also sometimes been resorted to by explorers 

 in an extremity, but it is very indigestible and has little to recommend it. 



13A 



