FILICES. 127 



necessarily grow in woods, but the most typical plants that I ever 

 saw were in a cliff with a northern aspect, in the wood north of Lady 

 Kinnear's cottage on the Lakes of Killarney. When I first saw it the 

 trees had been cut away from it, having the cliff quite covered with 

 such a marked variety of the fern that I firmly believed it must be a 

 distinct species. Five or six years afterwards I visited the place, and 

 found the trees amazingly grown, and that only in the still exposed 

 places grew the A. acutum, while in the places shaded by the trees it 

 was replaced by the normal form." It seems curious that increased 

 shade should cause the acutum to pass into the normal form ; 

 I should have expected the reverse to happen. 



A. Adiantum-nigrum can scarcely be confounded with any other 

 British fern, except perhaps A. lanceolatum, from which it differs in 

 its fronds being much thicker and firmer in texture, and with the 

 lower pinna? much larger, so that the frond is triangular or even sub- 

 deltoid rather than lanceolate. The sori are much longer and more 

 remote from the margin of the pinnules and segments than in 

 A. lanceolatum, and the scales at the base of the stipes are longer 

 and more attenuated, generally with only a single longitudinal rib 

 of thickened tissue towards the apex. 



Black Spleenwort. 



SPECIES IV.— A SPLENIUM MARINUM. Linn. 



Plate 1876. 



Caudex short, tufted, divided into several scaly crowns ; scales 

 linear-lanceolate, entire, tapering into long setaceous points. Fronds 

 several from each crown, spreading or pendent. Stipes rather 

 slender but not wiry, from one quarter to as long as the lamina, 

 purplish-brown, margined with green in the upper part, with a few 

 scattered hair-like deciduous dark-brown scales. Lamina thick, 

 coriaceous, glabrous, shining, evergreen, strapshaped or oblong-strap- 

 shaped or triangular-strapshaped, abrupt or tapering towards the 

 base, and always tapering towards the apex, pinnate ; lowest pair of 

 pinna? smaller than or equalling the succeeding pair, very shortly 

 stalked or subsessile, decurrent, spreading or ascending-spreading, 

 rhomboidal-ovate or rhomboidal-oblong or rhomboidal-strapshaped or 

 trapezoidal-rhombic or strapshaped-triangular, entire and rectangular 

 or inversely-deltoid or wedgeshaped at the base (which is usually 

 unequal-sided), obtuse or acute, crenate or crenate-serrate or slightly 

 lobed, more rarely serrate or incised ; middle pinnae similar to 

 the basal ones, and equalling them, but sometimes a little larger ; all 

 decurrent ; terminal pinna3 smaller and confluent. Rachis more or 



