LICHENS. 'J'] 



are valueless from the tissue being destroyed by the 

 mycelium. Fungi do not, and cannot, flourish on 

 'Trowing and vigorous bark, but on diseased, dead, or 

 decaying spots. 



Lichens obtain the greater portion of their pabulum 

 from the atmosphere, and only their mineral con- 

 stituents from the matrix. Fungi obtain their chief 

 support from the decaying vegetable matter on which 

 they flourish, gathering up the nitrogenous results of 

 decay, and disintegrating the matrix on which they 

 prey. Lichens are preservers, whilst fungi are de- 

 stroyers. 



Lichens, in their chemical composition, contain a 

 large number of substances which are wholly un- 

 known amongst fungi. Likewise they hold but a 

 small percentage of water, as compared with fungi, 

 so that in dessication they do not shrivel, collapse, 

 or diminish perceptibly in size ; whereas fungi shrivel, 

 and collapse, and are constantly liable to the attacks 

 of insects, or, if damp, to the development of mould. 

 Lichens may be preserved for years without fear of 

 insect or mould. 



The contention was also opposed on the ground 

 that the gonidia are a part of the lichen structure, 

 and arc consequently not appropriated green algcu. 

 Lichenologists, with one consent, admit them as 

 essential parts of lichen structure. One says that 

 they may be regarded as intermediate in function 

 between the vegetative and reproductive cell, assuming 

 the offices, and partaking of the characters of both. 

 Nylander contends that the absurdity of the hypo- 

 thesis is evident from the very consideration that it 



