Hart's-tongue Fern

Appearance

The plants are unusual in being ferns with simple, undivided fronds. The tongue-shaped leaves have given rise to the common name "Hart's tongue fern"; a hart being an adult male red deer. The sori pattern is reminiscent of a centipede's legs, and "scolopendrium" is Latin for "centipede". The leaves are 10–60 cm long and 3–6 cm broad, with sori arranged in rows perpendicular to the rachis.

Naming

The Latin specific epithet "scolopendrium" is derived from the Greek "skolopendra", meaning a centipede or millipede. The underside of the fronds supposedly resembles those insects.

Distribution

"Asplenium scolopendrium" is a common diploid species in Europe. In North America it occurs in rare, widely scattered populations that have been given varietal status, "A. scolopendrium" var. "americanum". Morphological differences are minor, but the North American populations are tetraploid.

The plants grow on neutral and lime-rich substrates, including moist soil and damp crevices in old walls, most commonly in shaded situations but occasionally in full sun; plants in full sun are usually stunted and yellowish in colour, while those in full shade are dark green and luxuriant. The rare occurrences of the North American form in the southeastern US are found exclusively in sinkhole pits. These populations may be relics of cooler Pleistocene climates.

In the United States, "A. scolopendrium" var. "americanum" was declared endangered in 1989. The reason that the European variety is relatively widespread, and the American variety a rarity, has apparently not been established. A third variety, "A. scolopendrium" var. "lindenii", occurs in southern Mexico and Hispaniola.

"A. scolopendrium" var. "americanum" grows in a small number of caves in the United States, two of them being in Alabama. One is Fern Cave, a public cave in Jackson County, Alabama, where it has declined heavily due to illegal plant collecting. The other is located at an undisclosed pit in Morgan County that is off limits due to the land around it being both protected by private landowners and the National Speleological Society.

Habitat

"Asplenium scolopendrium" is a common diploid species in Europe. In North America it occurs in rare, widely scattered populations that have been given varietal status, "A. scolopendrium" var. "americanum". Morphological differences are minor, but the North American populations are tetraploid.

The plants grow on neutral and lime-rich substrates, including moist soil and damp crevices in old walls, most commonly in shaded situations but occasionally in full sun; plants in full sun are usually stunted and yellowish in colour, while those in full shade are dark green and luxuriant. The rare occurrences of the North American form in the southeastern US are found exclusively in sinkhole pits. These populations may be relics of cooler Pleistocene climates.

In the United States, "A. scolopendrium" var. "americanum" was declared endangered in 1989. The reason that the European variety is relatively widespread, and the American variety a rarity, has apparently not been established. A third variety, "A. scolopendrium" var. "lindenii", occurs in southern Mexico and Hispaniola.

"A. scolopendrium" var. "americanum" grows in a small number of caves in the United States, two of them being in Alabama. One is Fern Cave, a public cave in Jackson County, Alabama, where it has declined heavily due to illegal plant collecting. The other is located at an undisclosed pit in Morgan County that is off limits due to the land around it being both protected by private landowners and the National Speleological Society.