Species of the Week
Number 14 -- September 4, 2006

In the Species of the Week feature of the Wildwood Web we took a close look at one of the species that lives in Wildwood.  To see the earlier featured species check the Species of the Week archives.

Walking Fern Asplenium rhizophyllum Walking fern is our first species of the week that is not a flowering plant.  It produces no flowers or fruits or seeds.  Instead it reproduces by producing spores.  The spores germinate to produce a tiny plant, rarely seen, which produces eggs and sperm.  When the sperm swims to the egg, a new baby walking fern begins to grow.  Walking fern also has another, asexual, way of reproducing.  If the long extended leaf tip touches soil, a new plantlet can form at the tip, produce roots, and become a new plant.  The new plant can then grow a long leaf which touches the ground and sprouts another plantlet.  In this way the colony gets larger and larger.

Most ferns have highly dissected leaves, but walking fern's leaf is a simple long narrow triangle with a rounded, somewhat heart-shaped base.  The tip of the triangle is extended into a long thin appendage, as seen in the picture above.  It is from the tip of this extension that a new plant can form, enabling the plant to "walk."

Walking fern is found from Quebec and Ontario south to Alabama, Arkansas and Oklahoma, but it is usually described as rare and local in the guidebooks.  It grows on cool, shaded limestone outcroppings in forests.  Such outcroppings are not really rare in our area, but they are local.  Walking fern can therefore be found in local colonies in shady ravines with limestone rocks throughout the area.  In Wildwood look for it along the trail on the west side of the ravine, between the spur trail to Adam's Cave and the southernmost bikeway bridge over Connelly's run.  There are many rock outcrops in this area with walking fern colonies at the base of the rocks.  A pair of binoculars will help you spot them from the trail and see the interesting leaf shape.  It is evergreen, which means you can see it any time of the year, unless it is covered by snow or fallen leaves.  In the winter, however, it tends to hug the ground, making it harder to see.

Walking fern is in the Aspleniaceae or Spleenwort Family.  The family name and the genus name both come from the Greek splen meaning spleen.  The common name of the family also refers to the spleen; "wort" is an old term simply meaning plant.  All these names reflect the use of some plants in the genus  for treating diseases of the spleen.  Whether they actually worked for this purpose, I do not know.  The species name rhizophyllum comes from rhizo, "root" and phyllum, "leaf," and thus means "rooting leaf," in reference to the plantlets that grow from the leaf tip.  In some guide books it is called Camptosorus rhizophyllum.  The genus name Camptosorus always sounded to me more like the name of a dinosaur than a fern.  It comes from the Greek and means "bent sorus," in reference to the spore-forming organs, the sori, which have a bent shape.  Walking fern was moved to the genus Asplenium because it is able to hybridize with several members of this genus, producing sterile offspring. This is like crossing a horse and a donkey to get a sterile mule, and is considered an indication of close relationship.

GGC