THE UNILATERAL FILM KKRX. 



Frond* smooth, pellucid-iucmbrannceous, minutely cellular, dark green, from ono or two, to five or 

 six inches long, oblong or linear i, e. elongate-oblong, pinnate. Pinna decurrcnt in tho upper part 

 and there forming a narrow wing to tho rachis ; distinct below ; curved backwards, subuniloteral, 

 wedge-shaped in circumscription ; digitntcly pinnntifid, i. c. two or three times dichotomously forke<l, 

 without an axial vein, the segments developed on the anterior side. Ultimate segments linear, obtuse, 

 spiuulosely sen-ate. Luxuriant fronds have a tendency to become branched. 



Venation consisting of two or three dichotomous ramifications of the wiry ribs, which branch alter- 

 nately from the main rachis; each ultimate segment having one of these branches along its centre, 

 not quite reaching to tho njwx, 



Fructification produced on the upper parts of each annual growth, extra-marginal as in 

 //. tunbndgnm. Son consisting of sessile spore-cases, clustered around the short receptacle. Recep- 

 tacle free, central, spongy, oblong, club-shaped, shorter than tho valves of tho involucre. Intolucm* 

 supra-axillary, more or less obviously stalked, curved forwards, i. v. in a direction opposite to that of 

 the segments; inflated, two-valved, tho valves ovate-oblong, strongly convex, and quite entire at the 

 edges, which are at first closed, but at length Uccomo gaping. Sjxne-cases sessile, vertically com- 

 pressed, thus lenticular, obliquely affixed. Spares minute, irregularly oblong. In some instances, 

 especially where the frond becomes branched at the apex, numerous son are bon.o without order 

 on the segments, but usually they are confined to one on each pinna, next tho rachis, as in 

 //. tunMdgewe. 



Duration. Tho rhizome is perennial. The fronds are perennial, enduring for two or thrco years, 

 or more, renewing their growth annually, as occurs in Lycopodium annotinum. 



We are indebted to Mr. F. Clowes, of Windermere, for the interesting observation that the fronds 

 of this species of HymenophyUvm resume their growth after the first year, unlike those of //. tan- 

 totigeme, which complete their growth in one season. Mr. Clowes gives tho following account of his 

 observations :— " I have a largo plant of //. ttmbridgense and of //. unilatcrtdc, which were put into 

 a case in March, 1854. Both are growing vigorously. But I remark that all the fronds of //. tunbrid- 

 gensc arc annual— I mean, they come up in spring, bear fruit more or less, persist more or less, but 

 never grow more than ono year. Those of//. unilaU-ralv, on the contrary, go on growing year after 

 year*. A great, number of the fronds which were on tho plants when placed in tho cose went on 

 growing, bore fruit at or near the extremity of tho fronds that year, grew on again last year, and 

 bore fruit, "ud are doing tho same this year (185(1), so that some fronds are ton inches long, and 

 wide in proportion. This is not the effect of cultivation, as tho wild plant does exactly tho same- 

 growing ' annotiuously,' in fact, but without distinct marks between the growths." 



The cultivation of the Film Ferns is an object of much interest to the fanciers of British Ferns. 

 Tho plants require a glass covering to preserve about them a constantly moist atmosphere, and 

 constant, but not stagnant, moisture, should bo maintained about their roots. These are their main 

 requirement*, and it matters little how thoy are applied, whether in a Wardian case, or beneath a 

 common bell-glass. Wo learn from Mr. Clowes, whose success is evident from his remarks already 

 quoted, that tho bell-glasses ought always to have two small apertures, as vents, near the top of 

 tho glass. Until he adopted this expedient, his efforts to cultivate the Film Ferns were attended 

 with but little success. 



I'M 



