Worldwide there are over 12,000
species of ferns.
The Wet Tropics is home to 65%
of Australia's fern species.
In Australia there are 390
native species of ferns, 47 species of fern allies, 44 species of conifers
and 39 of them are endemic.
Forty fern species are endemic to the Wet
Epiphytic ferns are one of the
most common features in rainforests.
They grow on the trunks and
limbs of trees but unlike parasitic plants such as mistletoe, do not steal
nutrients from their host tree.
They survive instead on
rainwater and the nutrients they get from trapped fallen leaves.
Sometimes the host tree taps
into the fern though. Roots have been found growing from the host tree into
'The Name Gondwana, given to
the original super continent of Australia was a part, comes from a region of
India where the fossil seed fern Glossopteris was first described. The
widespread geographic distribution of this genus in ancient times was one of the
clues which led to the realisation that the continents had once been joined.'
Environmental Protection Agency, Cairns.
& Reproduction of Ferns
'Most ferns love the tropics
where the warm moist conditions, not unlike those in which they evolved, suit
their requirements. As a result the Wet Tropics is home to a wide range of
relict ferns- species which have survived from the earliest times. They
represent all the major evolutionary fern groups.'
In the evolutionary development
of plants, ferns represent a great advance on all previous models. The
surface cells of an aquatic algae are able to absorb nutrients and water, on
land it is necessary to divide up the tasks, a step which makes the plants
- Roots were a revolutionary new feature
dedicated to seeking out less accessible sources of water, thus allowing
plants to move inland.
- They also served to stabilise the larger
- Water and nutrients, taken up by the roots,
had to reach other parts of the plant so a plumbing system - the vascular
- Woody vessels (xylem) performed this function,
moving water and nutrients upwards.
- These vessels had a duel function, providing
rigidity to the tissues.
- With these load-bearing structures the plants
were able to grow much taller and reach up to the light.
- Leaves were another fern invention - a system of
solar panels dedicated to capturing the energy of the sun and turning it
- Exposed to the air, these had to be sealed to
prevent the water gathered by the roots from leaking away so a waxy skin
(cuticle) was developed.
- Since the process of photosynthesis requires
an intake of carbon dioxide from the atmosphere and waste oxygen must be
released, special design features in the cuticle - pores - allowed this
exchange of gases to continue.
- Another plumbing system was needed to move the
sugars and other photosynthetic products from the leaves to the rest of the
- This function was performed by another new
system of vessels, the phloem.
- Although ferns were among the earliest
vascular plants (algae, lichens, mosses and liverworts are all classified as
non-vascular plants) they were not the only ones.
- The fossil records tell us that at one time
the world was dominated by massive clubmosses, giant horsetails and others
which created magnificent forests 45m or more in height as they used their
newly developed vascular systems to reach higher and higher in competition
- Many of these plants are now extinct, their
relatives hanging on comparative obscurity.
links with the past
ferns are structurally more advanced than mosses, like the more primitive
algae and mosses their sex life involves two generations and a dependence on
are produced by the fern plant in spore cases, usually beneath the leaf.
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.
the presence of water, the sperm burst free from the thallus and, attracted
by chemicals, swim to the female cells.
fertilisation, an adult plant develops, eventually dwarfing its `parent'
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.
produce sex cells.
ferns can, of course, increase their numbers asexually by spreading their
rhizomes-stems which are either below the soil surface or just above
grow down from the rhizomes while fronds sprout from the top.
Environmental Protection Agency, Cairns.
While many of the plants
in the rainforest have been around for millions of years, ferns have been around
for much longer than that! They appeared in the fossil record dating back to 325
million years ago. They are one of the earliest vascular plant forms on the
planet (plants which circulate water internally) and they preceded the flowering
plants, the conifers and even the cycads - all of which have a more advanced
means of reproduction. 40 species of ferns are endemic to the Wet Tropics (occur
nowhere else) and there are many interesting species but only a few special ones
are profiled here.
The King Fern (Angiopteris
evecta) looks superficially more like a palm crown growing directly out of
the ground but this is actually a relic fern from the late Paleozoic era. This
is the only species from its genus in Australia but it does occur elsewhere in
Southeast Asia/Oceania. The fronds might be the longest in the world for a fern,
reaching as much as 5m (16 ½ feet). 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. The Scaly Tree
fern (Cyathea cooperi) is an attractive and characteristic tree fern with
its node scars (scales) covering its narrow trunk and horizontal crown of
feathery fronds. The crown is said to reach up to 12 m (40 feet) wide and sits
atop a thin trunk reaching up to 12 m (40 feet) tall. This species isn't
restricted to the Wet Tropics and can be found in forests further down the east
coast of Australia.
A primitive looking fern
indeed is the Tassel fern and with good reason - its fossils have been
identified to much larger specimens from the Carboniferous
period. Two very different forms of the Tassel fern (also known as Clubmoss)
are almost opposite to each other in habit. The first is a ground creeping
version sometimes called the Pine Tree fern (Lycopodiella cernua) as it
resembles miniature pine trees only 25cm (10 inches) tall. It prefers open sun
and spreads along the ground, sending up vertical stems from along its length.
If any of the tips of the erect fern should meet the soil, a new plant sprouts
from the tip and grows upward to become a new vertical plant that sends out
creepers. Visitors to the Flecker Botanic Gardens in Cairns can see this plant
The other Tassel fern
group of interest is an epiphytic one (grows on top of another plant but is not
parasitic) which has been grown frequently as a hanging plant. The Common Tassel
fern (Huperzia phlegmaria) likes warm, humid conditions with good air
flow. At the end of each long "cat-tail" is a shorter green stem with
tiny cones along its length. These contain the material for a most interesting
means of reproduction: the cones release spores which drop into water, some
spores being male and others being female. These spores are then fertilised in
the water as they collide, becoming a seed which can then sprout a new plant.
Wet Tropics Management Authority.