18 FIRST STEPS IN GENERAL KNOWLEDGE. 



father; "these, as you know, are very common 

 on trees as well as on buildings. They gain their 

 nourishment from the atmosphere, and not from 

 the material on which they grow ; therefore they 

 are not so injurious as the fungus, which is fed out 

 of the very substance of what it grows upon." 



"How delighted we were," said Mary, "when 

 you first taught us to find lichens ! We had no 

 idea that the yellow and white patches on the 

 bark of the elm-trees, and the brown and gray 

 spots on the walls of our house, were all living 

 vegetables. And then, what beautiful pale gray 

 lichens we found on the church porch, and even 

 on the tombstones ! they were so flat and close to 

 the stone that they looked like stains." 



"Without lichens," said her father, " our land- 

 scapes would lose much of their picturesque 

 beauty, and our ancient edifices much of their 

 venerable character. It is remarkable in large 

 and smoky cities, where lichens do not flourish, 

 how much less interesting is the appearance of the 

 old buildings. The harmonious colouring of these 

 little plants is there greatly missed." 



" Are lichens of any use, papa ?" asked Eobert. 



" They are of great use in several ways. They 



