The Original Mystery Plant

Photo by John Nelson

Ferns represent an extremely ancient plant lineage, easily dating back to the early Carboniferous period, some 345 million years ago, and well before the first dinosaurs.

Ferns and their relatives were instrumental in the development of vast deposits of coal as they died and decayed, and their fossils are commonly encountered. Modern ferns are vascular plants, meaning their roots, stems, and leaves contain various tissues that transport water and dissolved substances.

Ferns do not produce flowers and don't produce seeds in the way that flowering plants do. Instead, ferns and their relatives reproduce by spreading tiny spores, which commonly originate in specialized structures called sporangia. Sporangia are located on the lower sides of the fronds. Depending on the particular kind of fern, these sporangia will be arranged in a rather characteristic pattern, often as small, roughened dots on the divisions of the frond.

The mystery fern is somewhat unusual in having its sporangia not consigned to roughened dots as in many other ferns but rather at the margins of the fronds' ultimate divisions, where hidden away and protected by a thin, overlapping margin of leaf tissue.

It is a common fern species in deciduous forests all over the eastern United States, from New England to northern Florida, and as far west as Oklahoma. In the Southeast, you will find it in the piedmont and mountain counties, generally away from the coast.

It likes to grow in damp shady places, but it can be found in open sites. The plants come up from a horizontal stem that clings to the soil or to rocks, and each frond has a smooth, shiny, nearly black stalk. The frond is prominently divided into many divisions and looks like a fan. The divisions of the frond are delicate, affording a lovely shimmering effect in the slightest breezes especially near waterfalls.

Answer to this week's mystery plant

[Answer: "Maidenhair fern," Adiantum pedatum]

Dr. John Nelson is the curator of the USC Herbarium.

To learn more about the Herbarium, call 777-8196. The

department also offers free plant identification.

www.herbarium.org