1^(19. pRAEGER. — Asplcniiim Adianium-nignim. 17 



and very small quite linear acute segments, texture leathery, 

 plant glabrous dark green, shining, often hardy. The latter 

 include A . acutum Bory and A^. solidum Kunze. 



From the above quotations it is clear that a considerable 

 diversity of opinion exists as to the amount of deviation 

 from type which constitutes var. acutum. It seems obvious 

 from the descriptions and figures that these writers have 

 mostly not adopted Bory's diagnosis, but have made their 

 own descriptions from specimens which they took to be var. 

 acutum. This form is not an isolated and constant variety, 

 but every gradation is found from normal A, Adiantum- 

 nigrum on to the most extreme forms of acutum as figured 

 by NewTnan and Sowerby. 



Considering first the extreme forms, which certainly fall 

 within Bory's definition, examination of a large series of 

 specimens shows that these terminate in two types : — 



F. LINEARE (fig. l). 



Most developed lobes lanceolate to nearly linear, divided 

 almost to the midrib into linear segments ; not distinctly 

 stalked, the footstalk tending to be winged, as is also the tertiary 

 rachis into which it runs. 



This is the most extreme form, var. acuhim par excellence. 

 If held against the light (the best way of examining a fern), 

 the linear character of the subdivisions and tendency to 

 decurrence are very marked ; in the upper part of the frond 

 especially, and in the middle portion of the lower pinnae, 

 all the parts — the primary and secondary rachis, the lobes 

 and their subdivisions — are about the same width. 



So far as I know, this form is in Ireland confined to the 

 south-west. I have seen specimiens from — Upper Lake of 

 Killarney (Scully, Praeger) ; Kilcolgan Abbey (Scully) ; 

 Whitegate, E. Cork (R. A. Phillips). Here also belongs the 

 beautiful and extreme form figured by Newman in his 

 " History of British Ferns," and in the " Phytologist," 

 1854, P- 37' collected on Tore Mountain by Dr. Alchin. 

 It is the plant of Hooker and Arnott's description,-^ but not 

 of Hooker's " Species Filicum " nor " Student's Flora." 



^ " British Flora," 6th ed., 574, 1830, 



