ALGJE. 227 



for their escape. They are not at present of much 

 utility in medicine or the arts, but their name confirms 

 the opinion that they were formerly employed as med* 

 icinesin affections of the liver. 



4. ALGjE. 



This term, originally applied to marine plants, has 

 been employed in a more extensive sense, and embra- 

 ces among others, the Lichens which cling to the rock, 

 and the Byssi which appear chiefly to delight in the 

 damp atmosphere of the cellar. The Lichens, consti- 

 tuting a very extensive order, have been investigated 

 with great success by the learned Acharius of Sweden, 

 whose works " form a new aera in this department of 

 our science, and will probably be the basis of all sub- 

 sequent improvement."* The Lichens have nothing 

 analagous to the root, unless we are willing to regard 

 a3 such, the fibres which issue from the inferior sur- 

 face of the frond. And in many cases the place of these 

 fibres is supplied by a cement which attaches the plant 

 so closely to the smooth rock, that we can separate 

 them only with difficulty. The frond, Fig. 121, (de- 

 nominated thallus by Acharius,) is either a leaf-like 

 expansion, or it is branched, and like a shrub in minia- 

 ture, or it is a mere crust or powder, presenting in 

 each case a simple structure and consisting chiefly of 

 gelatine and mucilage. With regard to the fructifica- 

 tion of Lichens, Hedwig and Gaertner, both men of pri- 

 mary authority, maintain very different opinions. 



The former contends that he has detected in the in- 

 terior of the frond, small cells, which contain particle? 



» Smith, 



