115 



CHAPTER VI. 



CLASSIFICATION. 



c< Without system the field of Nature would be a pathless wilderness." 



White, of Selborne. 



In regard to their position in the scale of vegetation, 

 Lichens belong to the thallogenous (thallus or frond-bear- 

 ing) or cellular division of Cryptogamic plants ; they are 

 destitute of a vascular system, consisting, as we have seen, 

 entirely of various forms of cellular tissue. By their re- 

 productive system they are closely allied to the Fungi ; by 

 their vegetative system, to the Algse ; from both they are 

 distinguished by the presence of gonidia as an essential ele- 

 ment of their thallus. So close are the links which bind 

 the Lichens to the allied families of the Algse and Fungi, 

 that Algologists and Fungologists are constantly removing 

 certain genera or species from the Lichens ; while Licheno- 

 logists are on the other hand engaged in swelling the ranks 

 of the Lichens at the expense of the Algse or Fungi. Thus 



