GENERAL CHARACTERS OF LICHENS. 35 



beautiful objects for a low magnifying power of the microscope. 

 The budlike bodies, having the form of flat disks, like coins, 

 may often be seen to grow, whilst still contained in their re- 

 ceptacle, and even to graft themselves, as it were, on the parent 

 plant. 



34. The group of Cryptogamic plants termed Lichens, mostly 

 consists of dry, hard, scaly crusts, destitute of leaves and stems, 

 and even of anything bearing a resemblance to them ; they grow 

 upon bare walls, the trunks of old trees, and other such situa- 

 tions, in which they are much exposed +o light, and not abundantly 

 supplied with moisture. In their general structure they nearly 

 approach to the Sea- weeds ; and differ from them chiefly, in 

 being adapted to live in air, instead of in water. The dry hard 

 crust is usually of a greyish colour ; its upper surface, being ex- 

 posed to the light and warmth of the sun, performs the functions 



. 7. SCALY LICHEN. 



of leaves; whilst from beneath it there proceed a number of 

 minute hair-like filament 4 *, which serve both to fix it by clinging 

 to the substance on which it grows, and also, it may be believed, 

 for the absorption of fluid the chief uses of the roots in the 

 Flowering Plants. Lichens are among the slowest in growth of 

 all plants, and the least subject to alteration from decay. Whilst 

 alive, they scarcely exhibit any change through a long series of 

 years; and when dead, their forms and colours are scarcely 

 altered by being dried. 



35. There can be no doubt, that the greater part of this tribe 

 derive their nourishment from the atmosphere and its contained 

 moisture alone ; flourishing as they do upon sterile rocks, with- 

 out a particle of soil or mould in their neighbourhood. There 



o2 



