86 BRITISH FERNS. 



records it, on the authority of Dr. Young, as occurring at Dun- 

 donald, near Paisley, and at the Carse of Gowrie, on that of 

 Mr. James Macnab, Curator of the Horticultural Society's Ex- 

 perimental Garden at Edinburgh : in this country it scarcely ever 

 occurs in its natural habitat, the dry fissures of rocks ; Dove- 

 dale, in Derbyshire, Cheddar, in Somersetshire, and a rock on 

 the road between Caernarvon and Bangor, are the only three 

 instances in which I have positively ascertained that it grows in 

 such situations. It has apparently become naturalized in the 

 mortar of our walls and ancient buildings, where it selects 

 the dry parts, and if the lower portion of the walls be wet, it 

 eschews it altogether. 



The roots are short, but possess a remarkable power of pene- 

 trating the mortar ; they are of a brown colour, and somewhat 

 scaly : the rhizoma is tufted, brown, and scaly : the young 

 fronds make their appearance in May and June, arrive at per- 

 fection in August, and continue green throughout the winter ; 

 they are always fertile. 



A small portion only of the rachis is naked, and is beset more 

 or less thickly with pointed chaffy scales : the form of the frond 

 is linear, elongate, and pinnate or pinnatifid : the pinnae are 

 attached to the rachis by their entire base, and are sometimes 

 also connected with each other ; they are obtuse, rounded, and 

 crenate ; the entire under-surface of the frond is covered with 

 brown pointed scales, which have been thought in many respects 

 analogous to the indusium of other ferns. 



The lateral veins are few in number, alternate, and irregularly 

 branched ; they terminate before the margin of the pinna, and 

 are united or anastomose at their extremities, dividing the 

 pinna into a number of compartments. The anterior branch of 

 every lateral vein bears an elongate mass of thecae, which, unless 

 we consider the scales as analogous to an indusium, are perfectly 

 naked. These thecae appear to me to be attached to the back 

 of the vein, and to be forced aside by the mode in which they 

 are pressed by the surrounding scales. In many fronds I find 

 a mass of thecae attached to a lateral vein, which in each pinna 

 runs parallel with the rachis; Mr. Smith, of Kew, considers 

 that, in this mass, the thecae are so attached as to point towards 

 the rachis, while those of other masses point towards the mid- 

 vein: in examining a great number of specimens I certainly 

 find these have an inclination in the way alluded to by Mr. 



