SECT. I. CONSERVATIVE ORGANS. 233 



stance on which they grow by means of a number 

 of small fibres issuing from the edge or under 

 surface of the frond, as in many of the Lichens ; 

 or by means of a small cylindrical and bony sort 

 of substance issuing from its base or centre, as in 

 several of the Fuel. An example of the former 

 mode of radication may be seen in Lichen caninus ; 

 and of the latter in Fucus nodosus. 



The Frond. The figure and contexture of the Varieties. 

 frond differs so very much in the different genera 

 of this tribe, as well as in many of the different 

 species of the same genus, that it will be necessary 

 to describe it in each. 



In the Lichens it is often merely a sort of In Li- 



*f , 



powdery substance adhering to some accidental 

 basis of support ; or a flat and crustaceous expan- 

 sion ; or a leaf-like or shrub-like production ; or a 

 pulpy and gelatinous mass ; but uniformly of ter- 

 restrial habitat, growing upon the surface of the 

 ground, or on trunks and branches of trees, or on 

 decayed stakes and pales, or on stones and barren 

 rocks ; and found also in all climates and seasons, 

 being capable of resisting the cold and humidity 

 of winter, as well as the warmth and drought of 

 s mmer. 



In the Byssi it consists often of a number of Byssi. 

 finely feathered threads, finer than those of a cob- 

 web and closely matted together, which in their 

 aggregate appearance frequently resemble a piece 

 of soft and smooth velvet of a rich and beautiful 

 colour ; being also of terrestrial habitat, and grow- 



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