Although the members of the family Hymenophyllaceæ are largely tropical, we are fortunate in having three representatives in the United Kingdom. Two of these, both Filmy Ferns, are not so familiar to people as they might be, if folk were only a little more observant; whilst the Bristle Fern is only to be found in the South of Ireland. All the species require an abundance of moisture, and they attain their greatest perfection on rocks which are dripping with water. _Trichomanes radicans._ The generic name is said to be derived from two Greek words—_thrix_, “a hair,” and _manos_, “soft”; the specific name is obviously connected with the Latin _radix_, “a root,” and has reference to the creeping rhizome. The Bristle Fern. [Illustration: Trichomanes radicans. The Bristle Fern.] This species is quite one of the most beautiful of our native species. Its fronds are very graceful in form, and are of such a delicate texture as to be almost transparent. The general outline of the fronds is triangular in shape. The leaves, varying in length from three inches to a foot, rise from a black, creeping rhizome, which will often cover a large area on a moist rock with a perfect network. The stipes or bare portion of the frond is, as a rule, about the same length as the leafy portion. A singular feature is a wing-like margin which is present on the upper part of the leaf-stalk. The frond of the Bristle Fern is divided three or four times, the first of the pinnæ being placed alternately on either side of the rachis. The pinnules are deeply cut. The veins of the frond are very strongly marked. All the divisions of the leaf are more or less curled, so that the frond as a whole presents a curled appearance. The sporangia of the Bristle Fern are borne of the veins in the lobes of the fronds. These are produced in curious cup-shaped processes which are really formed by the margin of the leaf. The veins pass right through these receptacles and project beyond the outer edges, thus giving a curious bristly appearance to the frond as a whole. The Bristle Fern, as has been indicated, chiefly occurs in the South of Ireland. It has been discovered in several counties, though it seems to be best established in the Killarney district. Any attempt to cultivate this Fern will prove a failure, unless the plants are kept continuously under a close glass cover where the atmosphere is saturated with moisture. The Bristle Fern is evergreen. _Hymenophyllum tunbridgense._ The generic name is derived from two Greek words—_hymen_, “a membrane,” and _phyllon_, “a leaf”; _tunbridgense_ has reference to the fact that the species was first of all noticed at Tunbridge Wells. The Tunbridge Filmy Fern.