292 ADAPTATIONS AMONG ALPINE PLANTS 



The Lichens are exceedingly abundant plants in 

 the Alps, and very interesting organisms from many 

 points of view. Though in this volume we are only 

 concerned with the higher members (in the botanical 

 sense) of the vegetable kingdom, occurring within the 

 Alpine zone, we may, however, here make an excep- 

 tion and add a few remarks on the subject of the 

 Lichens. 



In addition to the Bearded Lichens, another, a 

 very different type, may be observed on almost any 

 large boulder. It will be frequently noticed that 

 yellow, green, or brown patches are to be seen firmly 

 encrusted on bare rocks, forming what might almost 

 be described as films, adhering closely to the surface, 

 and without any definite outline. These patches are 

 the Crustaceous Lichens. 



The Lichens are composite organisms ; that is to 

 say, the body of the Lichen is built up of two plants 

 living together, closely intertwined. One of these 

 plants is a member of the Algae, the group to which 

 the Seaweeds, etc., belong. The other is a Fungus. 

 The Alga, which is green, and the Fungus, which is 

 colourless, are so closely interwoven together that the 

 resulting structure, or Lichen, is quite dissimilar from 

 any single Alga or Fungus. The constituents of the 

 Lichen are not individually visible to the naked eye, 

 and it requires careful microscopic examination to 

 detect them. 



The life history of a Lichen is too complicated to 

 be entered into here. It may, however, be added 



