Synonyms: Camptosorus sibiricus, Antigramma rhizophylla (L.) J.Sm., Camptosorus rhizophyllus (L.) Link
Common Name: American Walking Fern
Asplenium rhizophyllum is a small fern whose undivided, evergreen leaves and long, narrow leaf tips, sometimes curving back and rooting, give it a highly distinctive appearance. It grows in tufts, often surrounded by child plants formed from the leaf tips. The leaves of younger plants tend to lie flat to the ground, while older plants have leaves more erect or arching.
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Roots and stipes:
It does not spread and form new plants via the roots. Its rhizomes (underground stems) are upright or nearly so, short, about 1 millimetre (0.04 in) in diameter, and generally unbranched. They bear dark brown or blackish, narrowly triangular or lance-shaped scales which are strongly clathrate (bearing a lattice-like pattern). The scales are 2 to 3 millimetres (0.08 to 0.1 in) long and 0.5 to 1 millimetre (0.02 to 0.04 in) wide (occasionally as narrow as 0.2 millimetres (0.008 in)) with untoothed margins. The stipe (the part of the stem below the leaf blade) is 0.5 to 12 centimetres (0.20 to 4.7 in) long (occasionally up to 15 centimetres (5.9 in) long), and ranges from one-tenth to one and one-half times the length of the blade. The stipe is reddish-brown and sometimes shiny at the base, becoming green above, and narrowly winged. Scales like those of the rhizome are present at the stipe base, changing to tiny club-shaped hairs above.
The leaf blades are not subdivided, as in most other ferns, but are narrowly triangular to linear or lance-shaped. Their shape can be quite variable, even on the same plant. They measure from 1 to 30 centimetres (0.4 to 10 in) long and from 0.5 to 5 centimetres (0.2 to 2 in) across and have a leathery texture with sparse hairs, more abundant below than above. The rachis (leaf axis) is dull green in color and almost devoid of hairs. On the underside of the blade, the veins are difficult to see and anastomose (split and rejoin each other), forming a series of areoles (the small areas enclosed by the veins) near the rachis. Fertile fronds are usually larger than sterile fronds, but their shape is otherwise the same. The base of the blade is typically heart-shaped (with the stipe protruding from the cleft); the bulges on either side of the cleft are frequently enlarged into auricles (rounded lobes), or occasionally into sharply-pointed, tapering lobes. The leaf tips may be rounded but are typically very long and attenuate (drawn out); the attenuate tips are capable of sprouting roots and growing into a new plant when the tip touches a surface suitable for growth. On rare occasions, the auricles at the leaf base will also take on an attenuate shape and form roots at the tip. The ability of the leaf tips to root and form a new plant at some distance from the parent gives the species its common name. The young leaves forming from a bud at the leaf tip are round to pointed at their apex, not yet having developed the long-attenuate shape.
Specimens of A. rhizophyllum with forked blades have been found in Arkansas and Missouri. The fork usually occurs in the tip, perhaps due to growth after insect damage, but one specimen was found forking from the upper part of the stipe.
Sori and spores:
Fertile fronds bear a large number of sori underneath, 1 to 4 millimetres (0.04 to 0.2 in) long, which are not arranged in any particular order. The sori are often fused where veins join, and may curve to follow the vein to which they are attached. The sori are covered by inconspicuous thin, white indusia with untoothed edges. Each sporangium in a sorus carries 64 spores. The diploid sporophyte has a chromosome number of 72.
Cultivation: This fern prefers light to dense shade, moist humid conditions, and thin rocky soil. It requires a sheltered location where there is protection from the wind.
Used medicinally by the Cherokee Indians. Those that dreamt of snakes drank a decoction of liverwort (Hepatica acutiloba) and walking fern to produce vomiting, after which dreams do not return.
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