Brittle Bladder Fern
BRITTLE BLADDER FERNCYSTOPTERIS FRAGILIS
Synonyms:
Cystea fragilis
Cynthia fragilis
Polypodium
The whole of the Brittle Bladder Fern genus consists of small fragile but beautiful and interesting ferns. They are all more delicate in texture than most of our native ferns. The generic name is derived from two Greek words, signifying bladder and fern, and refers to the form of the involucre. The present species has fronds from five to six inches high, growing in tufts. They are lanceolate and twice pinnate.
The stalk is erect, slender, dark-coloured, and almost without scales. The veining in the fronds is very evident, owing to their delicate and almost transparent texture. The mid-vein of the pinnules is somewhat winding, with a venule simple or divided, branching off to each lobe, one branch extending to the point of each marginal tooth. Almost each vein bears at its termination a cluster of capsules of a roundish form, which contain the seeds: these increase very rapidly, and at last become confluent.
This beautiful little fern is distributed widely over the United Kingdom, and prefers moist and mountainous districts, in the fissures of rocks, or the interstices of stone walls. It is rare in Ireland. It is found all over the world in favourable situations, extending even to the Arctic regions. The varieties are easily distinguished. They are;
CYSTOPTERIS FRAGILIS DENTATA, which is smaller than the original fern, and always blunter in form. The veining is similar, but the fructification is at the margin and not near the middle of the secondary vein. One great distinction from the Brittle Bladder Fern is that the clusters of sori as they ripen form a brown ridge on the under surface of the pinnules. It is found in the north of England chiefly.
CYSTOPTERIS DICKIEANA is a variety of fragilis having a very compact frond. It may be distinguished by its deflexed overlapping pinnae; the pinnules decurrent, broad, obtuse, with a few shallow marginal teeth. It is of a deep green colour and very transparent. It has only been found by Dr. Dickie in sea-caves near Aberdeen, after whom it was named.
Few ferns can be cultivated with greater facility than these. They may be grown in the open garden-border, or in close cases; they do best, however, in the open air, as they are subject to the attacks of a red mildew, which is increased by confinement.