THE BLACK SPLEENWORT. 29 



leathery sort of texture, and are much veined. It is 

 found only very sparingly in Ireland. This fern does 

 not thrive well in the closed case, but does best on 

 rock-work in the open air, in a shady situation. 



When this fern assumes a much more blunt form, 

 it constitutes the variety called by botanists Aspidium 

 Adiantum nigrum obtusum ; while sometimes it ac- 

 quires a tapering slender shape, and is then called 

 Aspidium Adiantum nigrum acutum ; both these 

 forms are rare in this country on the Continent they 

 are well known, and are considered so permanent as 

 to be ranked as species. 



