Oak Fern
OAK FERNPOLYPODIUM DRYOPTERIS
Synonyms:
Gymnocarpium Dryopteris
Polystichum Dryopteris
The Oak Fern is one of the most delicate and elegant of our species of ferns. The roots are creeping, fibrous, and black, forming a dense, matted mass. The young fronds make their appearance in March and April, as Mr. Newman expresses it, "Each at first resembling three little balls on wires." These balls gradually unfold, and display the triple character of the frond. They soon arrive at maturity, and are often loaded with fruit as early as June: they disappear in the autumn. The stem is very slender, purple, and shining, and is frequently twice as Ion- as the frond. There are a few scattered scales towards the base. The fronds are slender and delicate, broadly triangular or rhomboidal, with three branches; the dursions pinnate; the pinnae cut into segments nearly to the mid-rib; the uppermost entire. The colour is a brighter green than almost any other British fern, which, however, it is apt to lose if too much exposed to the sun. The sori are borne on the margins of the segments.
This pretty and delicate fern occurs chiefly in wild mountainous districts, wet woods, and the vicinity of waterfalls, in our northern English, Welsh, and Scotch counties. In Ireland it is a fern of great rarity. Throughout Europe it is very generally distributed.
This is peculiarly a shade-loving fern. Besides the delicate texture and graceful habit, the vivid green hue of its foliage is its great attraction, and cannot be preserved in exposed situations. Although a free supply of moisture is recommended, care must be taken that it does not remain stagnant, as it will speedily destroy the plant by the decay of the rhizoma. By care and attention to these facts, this beautiful little fern will be found a pleasing and satisfactory addition to a fernery. From its small size, it is well suited for a fern case.
Variety:
POLYPODIUM CALCAREUM, or the Limestone Polypody (known also as Polypdium Robertiana), appears to be merely a variety of the Oak Polypody, of stouter growth, and occurring in limestone districts. Its chief distinctions consist in the pinnate rather than the ternate divisions of the fronds, which have a glandular, mealy, or tubescent appearance. In development, the fronds never assume the appearance of the three little balls, as in Dryopteris. It is of a darker duller green; its stalk is more scaly at the lower part-green instead of purple, and the clusters of sori more densely crowded. It is found commonly in Derbyshire, near Matlock, and abundantly in Cumberland, Westmoreland, Yorkshire, and Lancashire. It does not seem to have been found in Scotland or Ireland.
The mealy dust which characterises this fern is a beautiful object under the microscope, each slender stem supporting a globular head; but as this appearance soon goes off when the specimen dries, it is best to examine freshly-gathered plants.
There seems to be no great difficulty in cultivating this fern in the ordinary soil of gardens, although it does not thrive so well as some others in the atmosphere of towns. When grown in the greenhouse, it should be planted in large pans, with a free admixture of limestone and crumbled and sifted mortar; full exposure to the sun has rather a beneficial effect on it than otherwise.