Major Groups, Families and Genera

Ferns and Fern Allies

What are ferns and fern allies?

Ferns (Pterophyta) and the distantly related Psilophyta; Sphenophyta (horsetails) and Lycophyta (clubmosses and quillworts) occur all over the world. They are the only group of higher vascular plants to have two independent-living stages to their lifecycle: the spore-producing stage (sporophyte) and then the miniscule gametophyte (prothallal) stage. This second stage is where the sex organs are located and fertilisation takes place via mobile sperm in a water film. Two further unique characteristics are the tightly coiled spiral that is the "fiddlehead" (or crozier) of most ferns and the spore-capsule (sporangium) with its wonderful ballista action.

There are approximately 11,000 species of ferns (arranged within 318 genera and 36 families at Kew) and 1,200 fern-allies (in 10 genera with five families). They are descended from relatives dating back almost 400 million years, indeed modern Equisetum is almost identical to fossil Equisetites (elephant ferns) of 300 million years ago! That said, most fern genera existing today have no reliable fossil relatives. Rather they can be viewed as a reduced but but diverse assemblage of actively evolving species, able to hold their own alongside the considerably more numerous angiosperms.

The largest genera are Asplenium, with c. 900 species, Adiantum and Cyathea (tree ferns to 25m tall) with c. 700 each. The largest families are Dryopteridaceae (1,100 spp.) and Thelypteridaceae (950 spp.). Nearly all of the world's land habitats and ecological niches are occupied by pteridophytes. The greatest diversity of species is in the tropics, where they constitute an average of 7% of all vascular plant species of rainforests. Here, a large proportion are epiphytes, from tiny ferns with leaves barely 5mm long, to huge humus-gathering Drynaria ferns that can weigh 100kg or more.

The main tree fern genera are Cyathea in the family Cyatheaceae, and several genera in the family Dicksoniaceae of which Dicksonia is most important. Cyathea includes some 700+ species, many of which are poorly known. Like many other fern groups, the Old World Tropics (the tropical areas of Asia, Africa and the Western Pacific) is a major centre for species diversity. New Guinea alone has over 130 species,and nearly all are restricted to that island. The genus Dicksonia has one Australian species Dicksonia antarctica, whch is widely cultivated in southern England. An important centre for the diversity of this genus is New Guinea where there are six species, and material of several undescribed species has been collected.

Biodiversity in the Old World Tropics

The Old World Tropics is a major centre for biodiversity and includes areas which account for over 50% of the total number of species of ferns and fern allies. The island of New Guinea is probably the most diverse in the region as it includes over 2,000 species; Borneo includes some 1,200 species; and the Philippines around 1,000 species. There are still many undescribed species in the Old World Tropics and many are threatened, probably extinct, as a result of the extensive clearing of land for agriculture, particularly for oil palm plantations. In Papua (Irian Jaya ) we have collected many new species of tree ferns, some apparently endemic to local valleys around Mt Jaya (Mt Carstensz) - see discussion of the tree ferns below.

The many areas which still require extensive collecting include New Guinea, Sumatra, Sulawesi, Borneo in the Malesian region and Laos, Cambodia and Vietnam. It is very important that collections are made very carefully (see Collecting Ferns) and many books outline the general requirements for collecting ferns. The specialist data required for tree fern collections and collections of bird's nest ferns are outlined under tree ferns and Asplenium below.

Importance of ferns and fern allies

Weeds of agriculture

Equisetum arvense is one of the most invasive and doggedly persistent plants in the world, with underground stems and tubers that go very deep and are otherwise also difficult to destroy. Bracken (Pteridium) is frequently a problem if the land is not sensibly managed. Conversely, recent efforts at commercial harvesting of the "peat" formed by it have been successful.

Food

Although the Ostrich Fern (Matteuccia struthiopteris), which provides the popular North American "fiddleheads" is the only edible fern to be involved in international trade, young leaves of dozens of species of ferns form a prominent part in the diet of many people in the tropics - particularly South-east Asia including New Guinea. All are harvested from the wild, and can be seen covering whole market stalls. ecent research has shown that they are very nutritious. Bracken is eaten in some countries, but has been shown to be carcinogenic.

In the Old World tropics ferns are widely used in traditional societies as a source of vegetables in the diet of village people. Up to 16 species of ferns are eaten in traditional communities in Sarawak, most gathered from the forests. This accounts for 8-10% of all vegetable dishes (Christensen). Around 200 species of ferns are regularly eaten in the tropics. Many edible species have been recorded from the Old World tropics and they make a significant dietary contribution. Species include Helminthostachys zeylanica (Ophioglossaceae), Diplazium proliferum and Diplazium esculentum (Woodsiaceae) and many species of tree ferns (Cyathea Cyatheaceae). Lists of the species eaten have been prepared for many areas including Thailand (Jacquat 1990), New Guinea (Powell in Paijmans 1976) and the Solomon Islands (Henderson and Hancock 1988). There are many other references on edible ferns but those listed will give a good introduction. A table giving the nutritional values of some fern species is included in Christensen (Table 5).

Further reading:
Christensen, H. (1997). Uses of ferns in two Indigenous communities in Sarawak, Malaysia. Pp. 177 -192 in Johns, R.J. The Holttum Memorial Volume: Published to commemorate the centenary of the birth of Professor R.E. Holttum 1895 - 1995. The Royal Botanic Gardens, Kew.
Henderson, C.P. and Hancock, I.R. (1988). A guide to the useful plants of the Solomon Islands. 465 pp. Research Department, Ministry of Agriculture and Lands, Honiara, Solomon Islands.
Jacquat (1990). Plants from the markets of Thailand. 251 p. Editions Duang Kamol, Bangkok, Thailand.
Powell, J. in Paijmans, K. (1976). New Guinea vegetation. 212 p. Elsevier Scientific Publ. Co., Amsterdam.

Azolla, a small water fern that carries blue-green nitrogen-fixing alagae (Anabaena azollae), is a hugely important means of fertilising rice crops through China, southern Asia and Malesia and has been practiced and refined for centuries. This plant is the major source of nitrogen for growth in the rice paddies of Asia. Plants are carefully propagated from year to year. Because of its importance as the source of nitrogen for the growth of the rice plants in rice paddies, over two billion people are almost entirely dependent on this fern for their livelihood. In the field it can often be recognised by the brilliant red colour of the small plants floating in clear areas in swamps. It is estimated that each year Azolla converts more atmospheric nitrogen into a form available for plant growth than all the legumes.

Right: a patch of Azolla growing in lowland swamp forest in southern Papua (Irian Jaya), Indonesia. Photo: R.J. Johns
Drawing: Azolla pinnata

Further reading:
Lumpkin, T.A. and Plucknett, D.L. (1980). Azolla: Botany, physiology, and use as a green manure. Econ. Bot. 34: 111 - 153.

Humus and fodder is also provided, and all without the problems easily caused by artificial fertilisers.

Medicinal Use

A herbarium collection from Brunei Darusalam, made in the mid-1930s, records that plants of Helminthostachys zeylanica were collected for sale to be exported to use in China as a medicinal plant. Examination of the records compiled by Perry and Metzger (1980) show that this species is an important village medicine with a decoction being used to treat boils and ulcers. Rumphius noted that the rhizome was chewed with Areca to treat whooping cough and other reports indicate its use to treat dysentery. There are many records on the use of ferns and fern allies as medicines (see papers in Perry and Metzger and PROSEA) and also those above which often list medicinal uses as well as their use as vegetables.

Further reading:
Perry, L.M. and Metzger, J. 91980). Medicinal plants of east and south east Asia: attributed properties and uses. The MIT Press, Cambridge, Massachusetts and London, England.
PROSEA Plant resoures of South east Asia. Medicinal plants.

Insecticides

Recent research has concentrated on extracts from ferns that kill insects by inhibiting the shedding (ecdysis) of their "skin" (exoskeleton).

Horticulture

Many ferns are grown for ornament, especially Nephrolepis (Boston ferns), Adiantum (Maidenhair ferns), Dryopteris and Polystichum and there is a considerable amount of trade in these. The "florist's fern" is Rumohra adiantiformis, a pantropical plant with very thick leathery leaves which keep for days in or out of water. It is grown mostly in Florida and Costa Rica, and the international trade is worth millions of pounds. Tree ferns are cut by the million each year and their trunks used for growing other plants, particularly orchids.

Other uses

Beautiful vases are made from the trunks of Cyathea, the black and very hard vascular tissues forming elegant patterns. Lygodium is extensively used in Thailand to make a wide range of small boxes and baskets, and also body jewellery. Cyathea trunks are very strong and resistant to fungi and insects and are used to build huts and small houses in the tropics.

Conservation

Major changes have been proposed to the CITES regulations regarding tree ferns. It is important, however, that the current CITES regulations are still observed.

Research programmes

A major objective is the completion of the Ferns and Fern Allies for the Flora of Tropical East Africa.

In addition, databases exist for:

Dipteridaceae
Oleandraceae
Cyatheaceae
Aspleniaceae

Collections

Living Collections

The Royal Botanic Gardens, Kew, has a collection of living plants representing most of the families. The majority are grown in two public greenhouses (the Princess of Wales Conservatory and the Filmy Fern House), and one research greenhouse. Included are Lecanopteris ("ant-ferns", in the family Polypodiaceae), the high-climbing Lygodium (whose fronds can grow over 30m long), and the world's largest extant horsetail (in the Evolution House). Hardy species and cultivars can be found all over the gardens, particularly in the Rock Garden and Woodland Garden.

Economic Botany

Library

The botanical collections of most tree ferns are very poor and often lack much of the plant material required for careful description of the species. Even recent collections often do not include material of the stipe and rachis, little information about the lengths of the fronds, the length of the pinnae, etc. Many specimens still consist of a single pinna and lack many of the characters necessary for study and research.
It is time-consuming to achieve worthwhile collections of tree ferns, but it is very important if we are to sort out the taxonomy of this most interesting and diverse group. A major programme on the tree ferns of the Mount Jaya area in Papua (Irian Jaya) has been started as part of that project. In order to rectify the collections available, a proforma (in MS Word format) is available for those involved in the collection of tree ferns.

Volunteers from the Friends of Kew and Earthwatch Institute (UK) provide valuable asssistance.

Publications

Systematic publications