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Natural Perspective

The Plant Kingdom: Ferns and Allies (Filicinophyta)

(Last modified: 21 July 1997)
[photo Goldback Fern group]
Ferns represent the second major step in the evolutionary sophistication of plants. While they still reproduce by spores like mosses, the ferns add a vascular system -- i.e. specialized organs for trasporting fluids throughout the plant.

As an inidication of this extra evolution, the gametophyte stage of growth is significantly reduced. In this way, a fern can be thought of as the inverse of a moss. The moss plants we commonly see are gametophytes: the sporophyte stage is small and often overlooked. By contrast, the fern plants we commonly see are the sporophytes: it is the gametophyte stage that is small and often overlooked.

Ferns have a horticulural value in our society -- i.e. people are willing to consider intentionally adding ferns to our outdoor and indoor gardens -- and therefore we know more about them. Perhaps size is also a factor: ferns are big enough to catch our divided attention while we hike along a trail. Modern flora usually include keys for identifying ferns as well, thus further increasing their exposure to our roaming curiosity.

[photo Goldback Fern prothallium] [photo Goldback Fern prothallium&leaf] The gametophyte generation of ferns are small, heart-shaped, plants called prothallia (singular: prothallium). They are less than an inch (1 - 2 cm) in diameter and look very much like thalloid liverworts or hornworts. Male and female sex organs are located on the underside of the prothallium and, when conditions are right, the sperm swims from the male antheridium to fertilize the egg in the archegonium.

The result of this union is the fern plant we have come to know and recognize. This plant, the sporophyte, grows to maturity and then produces spores on the undersurface of its leaves or fronds. Fern sporophytes can grow as tall as trees. They can reproduce vegetatively from root cuttings. They never have flowers.
[photo Goldback Fern prothallium+leaf]

Ferns prefer to live in environments having low light and relatively high levels of moisture and humidity and. For reason they flourish in tropical forests. In fact, regardless of where they are, an abundance of ferns imparts an impression of the topical forests to human observers.

[photo Goldback Fern sporophyte]

Fern allies share the characteristics described here but do not have the ferns' stem and leaf structure. The most conspicuous of these allies is the Horse-tail plant.

All of the photos on this page show the Goldback Fern (Pentagramma triangularis)


Phylum: Filicinophyta (ferns)
Class:
Subclass: Schizaeidae
Family: Pteridaceae (Brake family)
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This site produced and maintained by Ari Kornfeld, email: (ari@perspective.com)
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Credits:
Collaboration and inspiration thanks to Susan Kornfeld
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Special thanks to Claire Doyle for scanning some early photos
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