EOCCELLA. 



133 



lopment only in tropical or warm climates, where however 

 it has a somewhat wide geographical range. 



2. Eoccella euciformis [fucus, a species of seaweed). 

 Thallus flattened or thong-like, irregularly divided, often 

 fan-shaped ; segments variously bent, naked or sorediiferous ; 

 apothecia lateral and superficial. 



It grows, like the preceding species, chiefly on maritime 

 rocks; but in some foreign countries it is found also on 

 trees, as at Pondicherry, in India, where its habitat is the 

 trunk of the Mangifera Indica. It occurs very sparingly 

 on the south coast of England, in the Channel Islands, and 

 on the adjacent islands and coasts of France. But it is only 

 in tropical Africa, Asia, and South America, that it reaches 

 its highest development ; on the coasts of these countries it 

 frequently attains great size, and has a very tough leathery 

 consistence. It usually has a greater abundance of apo- 

 thecia, and is more seldom warted or mealy, but more fre- 

 quently cracked and fissured, than R. tinctoria. Its colour is 

 generally tawny or ochroleucous, and it varies much in the 

 size and mode of division of its lacinise. Its geographical 

 range is greater than that of the preceding species. B. tinc- 

 toria and H. fuciformis may be considered types of the 

 most valuable dye-species of the genus Eoccella which we 



