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CHAPTER II. 



GENERAL CHARACTERS OE BRITISH LICHENS. 



" Some are reddish, some brown, some grey, and some black, 

 And they're puckered, edged, button'd, or fringed, front and back : 

 Some are lying like leather close under your feet, 

 Some waving from trees in the forest you'll meet."— Miss Twamlef. 



We shall here consider the minute or microscopic anatomy, 

 as well as the ordinary physical and chemical characters of 

 the vegetative and reproductive systems of Lichens, and shall 

 also review generally the biology of a Lichen, tracing the 

 various phases of its existence from its origin to its decay. 



The term Thallus (OaXkbs, a frond or green leaf,) is ge- 

 nerally employed to designate the vegetative system or mass 

 of nutritive organs of a Lichen. Though bearing no struc- 

 tural resemblance to either, it may be considered as combi- 

 ning the offices and supplying the place among the Lichens 

 of the stem, root, and leaves of the higher plants. In form 



