When released, each spore grows into a tiny heart-shaped structure known as the thallus which, in turn, produces male sperm cells at the pointed end and female cells in the notch. In the presence of water, the sperm burst free from the thallus and, attracted by chemicals, swim to the female cells. Curiously this large spore-producing fern plant is the equivalent of just the tiny spore capsule and stalk of the moss plant while the much more obvious green moss plant is the equivalent of the tiny fern thallus. Both produce sex cells. Many ferns can, of course, increase their numbers asexually by spreading their rhizomes-stems which are either below the soil surface or just above it.
Roots grow down from the rhizomes while fronds sprout from the top.
They appeared in the fossil record dating back to 325 million years ago. A good place to see King ferns is the Nandroya Falls track in Palmerston National Park, south of Cairns and along the road to Cape Tribulation. Promotional photographs of the Wet Tropics often feature the Tree Fern, a species which imparts a tropical yet ancient feel to the area. Tree ferns have been here since the dinosaurs but the modern species are only small versions of their ancestors. This species isn't restricted to the Wet Tropics and can be found in forests further down the east coast of Australia.