THE USES OP LICHENS. 17 



in the dyeing industry, lichens found a useful place 

 early in the history of civilization. 



I. THE P^UNCTION OF LICHENS IN NATURE. 



The task that lichens perform in the economy of 

 nature is indeed Herculean and out of all proportion 

 to their size. They are the hardy pioneers preparing 

 the way for the advance of the less hardy vegetation. 

 Their hardiness is shown by their ability to resist 

 greater extremes of temperature than any other plants, 

 or even animals. They have gained the reputation of 

 being able to live on nothing but air and sunlight. 

 This is, perhaps, scarcely true, but it is a fact that they 

 require less organic food than other plants. In gen- 

 eral, lichens are to be compared to green chlorophyll- 

 bearing plants, since they take up carbon dioxide from 

 the air and give off oxygen. They thus add their mite 

 toward keeping the air in a suitable condition for the 

 respiration of higher animals. 



The most important function that lichens perform 

 in nature is the preparation of soil. Many of the 

 crustose lichens occur upon the hardest rock, to which 

 they are closely attached, forming dirty grayish or 

 greenish patches. Erroneous opinions as to the man- 

 ner in which lichens disintegrate the rock are very 

 prevalent. A recent author puts it as follows : " One 

 peculiarity of some lichens is the power they have to 

 burrow into the hardest rocks, even flint and granite, 

 thus making for themselves homes (faveoli)." Other 

 authors make similar statements. Such statements 

 are wholly unscientific, hence untrue. No lichen, has 



