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POLYPODIUM

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Originally appearing in Volume V22, Page 38 of the 1911 Encyclopedia Britannica.
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POLYPODIUM , in See also:

botany, a large genus of true ferns (q.v.), widely distributed throughout the See also:world, but specially See also:developed in the tropics. The name is derived from Gr. arokvs, many, and arb&ov, a little See also:foot, on See also:account of the foot-like See also:appearance of the rhizome and its branches. The See also:species differ greatly in See also:size and See also:general appearance and in the See also:character of the frond; the sori or See also:groups of spore-cases (sporangia) are See also:borne on the back of the See also:leaf, are globose and naked, that is, are not covered with a membrane (indusium) (see fig. 1). The See also:common polypody (fig. 2) (P. vulgare) is widely diffused in the See also:British Isles, where it is found on walls, See also:banks, trees, &c.; the creeping, densely-scaly rootstock bears deeply pinnately cut fronds, the fertile ones bearing on the back the See also:bright yellow naked groups of sporangia (sori). It is also known as See also:adder's foot, See also:golden See also:maidenhair and See also:wood-See also:fern, and is the See also:oak-fern of the old herbals. back of leaf. There are a large number of varieties, differing chiefly in the See also:form and See also:division of the pinnae; See also:var. cambricum (origin-ally found in See also:Wales) has the pinnae themselves deeply cut into narrow segments; var. cornubiense is a very elegant plant with finely-divided fronds; var. cristatum is a handsome variety with fronds forking at the See also:apex and the tips of all the pinnae crested and curled. P. dryopteris, generally known as oak-fern, is a very graceful plant with delicate fronds, 6 to 12 in. See also:long, the three See also:main branches of which are themselves pinnately divided; it is found in dry, shady places in See also:mountain districts in See also:Great See also:Britain, but is very rare in See also:Ireland. P. phegopteris (beechfern) is a graceful species with a See also:black, slender See also:root-stock, from which the pinnate fronds rise on long stalks, generally about 12 in. long, including the stalk; it is characterized by having the See also:lower pinnae of the frond deflexed; it is generally distributed in Britain, though not common. Many other species from different parts of the world are known in See also:green-See also:house cultivation.

End of Article: POLYPODIUM

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