What are Pteridophytes

Deep in the forest, under the giant trees, lie the ancient pteridophytes, the ferns. They are not conspicuous or dominating, seldom reaching more than a meter or so high, with the exception of the tree ferns. They never flower and seldom are seen beyond the forest boundaries, except for the tough and sometimes pesky bracken ferns. Most people pay them little attention but they are important for two reasons. They are the descendants of explorers and conquerors, the first plant group to totally free themselves from their watery beginnings, turning the barren landscapes of ancient days green with their fronds and preparing the way for land afrom humble frogs to giant dinosaurs to the mammals and our own species. Without the ferns, the land would have remained uninhabitable.

They were the first plants to put up stout stems and thus reach above the ground beyond the low-lying mosses. They were the first plants to cover their delicate spores in water-proof cases that could survive in harsh terrestrial environments. Mosses were forever tied to moist microclimates because of the need for water to protect their reproductive stages and can never grow tall enough to reach new sources of sunlight because they have no solid stems. These two innovations allowed ferns to conquer the land and provide the food and shelter needed for the first land vertebrates. They were the first tracheophytes or vascular plants, having true stems with xylem and phloem, vascular tissues allowing the movement of water and nutrients through the plant.

Ferns first appear in the fossil record in the Carboniferous Age. Back in the first age of dinosaurs, the Triassic, the land was green but there were no flowering plants. The vast majority of plants were ferns and this was the period when ferns radiated out into all their diverse forms. Ferns covered the ground where grasses now grow. Ferns grew up to tree size to create the forests of the time. Countless generations of ferns lived and died, the producers of the ancient food chains, feeding the herbivorous dinosaurs and eventually making the great coal deposits that were to fuel the industrial revolution millions of years later.

Slowly they were supplanted by more advanced tracheophytes, those with true seeds, not spores. First the Gymnosperms or the cone- bearing seed plants evolved and then the all important Angiosperms or flowering plants. These plants succeeded because they developed better methods of reproduction. But though they lost their preeminence, the ferns did not go away. They are great survivors and are still with us to this day.

There are between twelve and twenty thousand species if ferns surviving in the world today, mostly in temperate to tropical ecosystems with abundant water. Ferns do not survive well in the desert or in extremely cold environments. The classification of modern ferns is difficult and complex. There are the true ferns, the equisetum ferns and then a number of smaller groups separated off due to various unique characteristics. The Australian National Herbarium webpage on ferns says their classification is a work in progress.

Many species of ferns are grown for pleasure. Maidenhair ferns are a well-loved house plant but easy to kill. At least I have always killed them, usually by not giving them enough water and then, feeling guilty, giving them too much. I was pleased therefore to find them growing wild on my land, on cool, wet, south-facing slopes (I am in the southern hemisphere so the south slopes are the cool wet ones, especially in winter when we face away from the sun). There, the maidenhairs grow lush in the dim light beneath the forest canopy as they have done for millions of years. Whenever I go into a new forest and I am trying to decide whether it is “old growth’ or disturbed forest, I look for ferns. If grasses predominate, I know that some disturbance has probably occured but if the ferns are thick and lush than it is possible that this forest is likely to have escaped the logging, grazing and burning practices that diminish their old growth status and value.

Out in the open in Australia, the tough bracken ferns compete for space with the grasses. They are tough, indigestible and toxic to cattle, so they have an economic importance, if negative. Their new fronds, called fiddlesticks, are edible and were a bush tucker food for the Aboriginal people. A number of ferns worldwide have been used as a food source by indigenous peoples. The aquatic mosquito ferns of Southeast Asia are used as biological fertilizers in rice paddies because of their ability to fix nitrogen. Some of the Equisetum ferns have traditional and alternative medicinal uses because of their high silicon content. The most important economic use of ferns however is as house plants.

So next time you walk in a forest, take notice the ferns and think about their long history and their evolutionary importance. They may seem insignificant but they have played an important part in the evolution of plant life and therefore all life on Earth.

References: http://www.anbg.gov.au/fern/