60 



wells, mines, and caverns. It varies greatly in size, according to 

 the locality : in the open vault, by the great hall in Conway Castle, 

 I have gathered fronds upwards of three feet long and nearly four 

 inches in breadth ; but in more exposed and drier situations their 

 ordinary length is from six inches to a foot. The rhizoma is very 

 compact and deeply rooted; it does not elongate, but increases 

 slowly by the formation of new crowns around the older, attaining 

 thus, when left undisturbed, considerable bulk and an almost sphe- 

 rical form. The fronds grow in circular tufts, unfolding at first in 

 an erect position, but afterwards radiating and curving outwards : 

 when springing from the side of a rock, or in the mouth of a well, 

 they are often pendulous : in outline they are linear-lanceolate or 

 strap-shaped, more or less acuminated at the apex and cordate be- 

 low, with an entire slightly- waved margin. The rachis is generally 

 of a dark purple hue, especially the petiolate portion, which con- 

 stitutes about a third or fourth of the length of the frond, some- 

 times smooth throughout, but more frequently beset with chaffy 

 membranous pale-brown scales, that give it a shaggy appearance, 

 and are often distributed along the under side of the midrib like- 

 wise. The parallel linear sori are usually very regular in their 

 disposition, but liable to vary in length, and sometimes form two 

 series, alternately longer and shorter : their peculiarity of develop- 

 ment has been already referred to, under the generic character of 

 Scolopendrium, and is illustrated, as well as the venation, in the 

 outline figure of a portion of the frond on our plate. 



So many deviations from the normal form are presented by the 

 varieties of this fern, and so closely do they approach each other, 

 that it is very difficult to select those deserving a separate notice. 

 In some instances the diversity arises from the division of the 

 rachis, in others from peculiarity in the marginal development of 

 the leaf, and occasionally from a combination of both. Among 

 the apparently endless and far from constant forms thus resulting, 

 the following, well known to the fern cultivator, are the most 

 marked and permanent : 



1. polyschides. Fronds narrow linear, deeply and irregularly 

 crenato-lobate on the margin. Moore, Handb. Brit. Ferns, 174, 

 fig. 8, 178. Phyllitis polyschides, Ray. 



The narrow linear form is the distinguishing character of this, 

 the division of the margin being often very obscure. The fronds 

 are generally fertile. 



2. crispum. Fronds thin, strap-shaped, the margins much undu- 

 lated or curled, the base cordate-auriculate. Moore. Handb. Brit. 

 Perm, 175, fig. 7, 178. 



The dilatation of the margin, which occasions the curled charac- 

 ter, is the probable cause of this very elegant and permanent variety 

 being almost uniformly barren. 



