FILICES. 01 



Rootstock capillary. Fronds convex, recurved, glabrous, trans- 

 lucent, consisting of a single layer of cells nearly twice as long 

 as broad, lanceolate-oblong or narrowly oblong, pinnatipartite, with 

 the pinna? all connected by a wing running down each side of the 

 rachis, and extending a short distance down the stipes ; pinnae 

 recurved, pinnatipartite, with the segments all on the anterior side of 

 the main vein, even in those at the base of the frond, simple or once 

 forked ; ultimate divisions strapshaped spinous-serrulate. Involucres 

 at the termination of the first anterior vein given off by the main vein 

 of the pinna?, ovate ; valves ovate, convex, entire throughout. Recep- 

 tacle without paraphyses. 



On rocks and trunks of trees, often growing with H. Tunbridgense, 

 but much more frequent, especially in the north-west of England 

 and Scotland, extending north to Orkney (where it was found by the 

 late Mr. Hecldle near the Kame of Hoy, and in 1880 by Mr. H. H. 

 Johnston on the Wart Hill of Hoy), and Shetland. Frequent in 

 mountainous districts in Ireland, especially in the west and north. 



England, Scotland, Ireland. Perennial. Summer, Autumn. 



Very similar to H, Tunbridgense in general appearance, and about 

 the same size. It is easily recognised when growing by its dark lurid 

 green fronds, recurved at the apex and margins, while in H. Tun- 

 bridgense they are flat and paler green. But even in the dried state 

 it may be known by the narrower pinnae, of which the main vein 

 branches only on the upper side, consequently they have the segments 

 all pointing towards the apex of the leaf, even in the basal leaflets. 

 The fronds are also rather narrower in outline, and their ultimate 

 divisions are rather broader and less parallel-sided. The involucres 

 are more exserted, a little larger, and with longer convex and entire 

 valves. The cells of the fronds are longer and narrower than in 

 H. Tunbridgense. Mr. Gulliver gives the average size of the cells 

 of H. Tunbridgense as -Ay inch each way, and in H. unilaterale, the 

 average long diameter g-i-g inch, and the short diameter -g-j-g inch. 

 (See ' Journ. Bot.' 1865, p. 204.) Mr. F. Clowes states that the fronds 

 of H. Tunbridgense die annually, while those of H. Wilsoni grow 

 on from year to year, like those of Trichomanes radicans, but 

 Mr. Moore says the fronds of H. Tunbridgense endure for " two or 

 three years under favourable circumstances." (' Nat. Print. Ferns, 5 

 8vo. ed. vol. ii. p. 304.) I have not had H. Tunbridgense in 

 cultivation, but I can corroborate the statement that the fronds of 

 H. unilaterale live for more than one year. 



Wilson's Filmy Fern. 



