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[ This set of files is an HTML version of a manuscript that was a precursor to a treatment of the aquatic pteridophytes of Papua New Guinea, published in G.J. Leach & P.L. Osborne (1985) Freshwater Plants of Papua New Guinea. It is presented here essentially as it was at the time, and users should be aware that references and collections made over the last 14 years have not been added and that taxonomy and nomenclature has not been updated accordingly. An update is intended, as time permits. - jrc ]

Introduction Keys, Descriptions Checklists Bibliography
Family Key Blechnaceae Isoetaceae Oleandraceae Polypodiaceae Salviniaceae
Azollaceae Equisetaceae Marsileaceae Parkeriaceae Pteridaceae Thelypteridaceae

The Aquatic Pteridophytes of New Guinea

J.R. Croft (c. 1986)

What is an aquatic plant?

The criteria used for the inclusion of species in this treatment of the aquatic pteridophytes of New Guinea is totally arbitrary. It is based on personal experience of plants growing in, or in association with, still or moving water bodies, supplemented by references to such plants in the botanical literature. Those totally immersed or free floating plants pose no problems, but the definition becomes blurred in the swampy and occasionally wet areas where water and land meet.

A broad concept of 'aquatic' has been applied according to the following definition: 'If, on a fine day, the collector gets arms and/or legs wet, then the plant is an aquatic'. The major exceptions to this rather simplistic definition are trees and epiphytes in swamp forests, including mangroves. There are no strictly marine pteridophytes.

The greatest difficulty is in selecting which of the fifty or more reophytic or river-side pteridophytes to include (see van Steenis 1981). In general, only those fully or partially wet for "significant periods" are described in detail in this treatment. Brief notes are provided on those remaining reophytes that occur sporadically below flood level, or are awash for only short periods.

Where is 'New Guinea'?

The geographical focus of this study is Papua New Guinea, an independent nation on the south-west Pacific rim. It includes the eastern half of the New Guinea mainland and adjacent islands, the Bismarck Archipelago and Bougainville. Papua New Guinea shares the New Guinea mainland with the Indonesian Province of Irian Jaya to the east and Bougainville is the north-western-most of a chain of islands that is otherwise the independent nation of th Solomon Islands.

The floras of these political units have a lot in common and national and administrative are totally artificial from a geographic and floralistic point of view. Thus specimens from the wider geographic unit of 'Papuasia' have been studied. This includes specimens Papua New Guinea itself and from immediately to the west in the Indonesian province of Irian Jaya and from the east in the remainder of the islands of the Solomon Islands chain (excluding Santa Cruz which is floristically and geographically part of the New Hebrides region). This was done to give a more complete view of the range of morphological variation and habitat tolerance of the species involved.

What is a Pteridophyte?

Pteridophytes are terrestrial, epiphytic, rupestral or aquatic (not marine), vascular plants with distinct alternating generations. The gametophyte is mall, relatively short-lived and avascular, producing the sexual organs antheridia (male) and archegonia (female). The sporophyte is the dominant generation, large and vascular, producing asexual spores which develop into the next generation of gametophytes.

In Papuasia there are 187 genera of pteridophytes covering approximately 1700 to 1800 species (there are over 300 genera ad 10,000 to 12,000 species of pteridophytes worldwide). The arrangement of families is always a matter of dispute among pteridologists, the number ranging c. 50 to less than 10; the aquatic families are not generally controversial, and in this treatment they are considered in their narrower senses. The present treatment recognises 11 families of true aquatic Papuasian pteridophytes with 13 genera and 21 species; if the rheophytes or occasionally flooded species were included this would swell to 55 genera with over 120 species, arranged in 26 families.

The descriptions and keys in this treatment (an in nearly every other treatment of ferns and their allies, for that matter) cover only the sporophyte generation, since this is the stage that most people see and are familiar with. The gametophyte and sexual stages of pteridophytes are for the most part very small and short-lived, and although they certainly offer useful diagnostic characters, they have only been studies for a very small proportion of the species. In all cases the gametophyte is filmy or succulent and can not exist for long periods without water; free water is required for the transfer of the male antherozoids to the famale archegonia, so in the broadest sense all pteridophytes must be regarded as aquatic for at least part of their life cycle.

The arrangement of this treatment

The pteridophytes are generally considered to be an unnatural collection of several unrelated groups that should have equal status to the Bryophyta (mosses and liverworts) and the Spermatophyta (seed plants). There are three such groups among the aquatic plants: Lycopsida (Isoetes); Sphenopsidae (Equsetum); Filicopsida (true ferns). However, in this treatment, for purely practical purposes, these divisions are ignored and each family of the ferns and their allies is treated alphabetically.

In this treatment the species have been arranged alphabetically under a genera which have been arranged alphabetically under families. In most cases there is little dispute about allocation of pteridophyte species in genera, and the generic concepts of Holttum (1959, 1971b etc.) have been adopted. However, there is almost total discord among botanists over the composition of pteridophyte families, with none of the dozens of schemes being able to claim majority acceptance (see Pichi-Sermolli 1973 for a summary). For purely practical reasons, and from no personal conviction, the family arrangement in this treatmnet follows that presented by Holttum in Willisí 'Dictionary of Flowering Plants and Ferns' (Willis 1973) which incorporate Pichi-Sermolliís concepts (see Pichi-Semolli 1970). For a sequential arrangement of the Pteridophyta for use in the curation of herbaria see that of Crabbe et al. (1975).

Because of the uncertainty of the definition of Pteridophyte families, detailed descriptions are not provided. As the aquatic families are represented by only one or two species in one or two genera in Papuasia, only the genera are described in detail, and a brief species description is provided highlighting significant differences from the genus as a whole and giving details of size, shape etc.

Species covered

The following species are accepted as aquatics, either obligate or facultative, and are treated fully in the taxonomic part:

Azollaceae: Azolla pinnata
Blechnaceae: Stenochlaena areolaris; Stenoclaena milnei; Stenoclaena palustris
Equisetaceae: Equisetum debile
Isoetaceae: Isoetes frigida [ ined. ]; Isoetes habbemensis; Isoetes neoguineensis; Isoetes stevensii
Marsileaceae: Marsilea crenata
Oleandraceae: Nephrolepsis biserrata; Nephrolepsis radicans
Parkeriaceae: Ceratopteris thalictroides
Polypodiaceae: Microsorium brassii; Microsorium pteropus; Microsorium ? schneideri (= Phymatosorus longissimus)
Pteridaceae: Acrostichum aureum; Acrostichum speciosum
Salviniaceae: Salvinia molesta
Thelypteridaceae: Ampelopteris prolifera; Cyclosorus interruptus; Thelypteris confluens

Other taxa are listed by family and by growth form and habitat but are not treated in full:

List of Papuasian aquatic pteridophytes
List of Australian aquatic pteridophytes


This treatment is based on the specimens under the care of the Papua New Guinea National Herbarium in Lae (Herb. LAE). Professor R.E. Holttum identified the rheophyte Tectaria trifida and provided nomenclatural information on Phymatosorus longissimus. Barbara Parris provided lists of species she considered to be aquatic or rheophytic, and habitat information. Illustrations for this treatment were prepared by Semeri Hitinuc and Taikika Iwagu, illustrators at the Division of Botany in Lae, Armstrong Bellamy of the Bulolo Forestry College, Barry Conn while employed as a botanist at the Division of Botany, and Jenni Marsh.

General references and regional treatments

Aston, H.I. 1973. Aquatic plants of Australia. A guide to the identification of the aquatic ferns and flowering plants of Australia, both native and naturalized. Melbourne Univ. Press. i-xv, 1 - 368, f. 1- 138, map 1 - 81.

Biswas, K. & Calder, C.C. 1955. Handbook of the common water and marsh plants of India and Burma, 1936. Health Bull. No. 24, Malaria Bureau No. 11 Gov. of India Press, Calcutta. Ed. 2. i - xvi, 1 - 177, pl. 1 -32.

Brownlie, G. 1969. Flore de la Nouvelle-Caledonie et dependances. 3. Pteridophytes. Mus. Nat. Hist. Natur., Paris. 1 - 307, pl. 1 - 39.

Brownlie, G. 1977. The pteridophyte flora of Fiji. Beih. Nova Hegwidia 55: 1 - 397, pl. 1-44

Cook, C.D.K., Gut, B.J., Rix, E.M., Schneller, J., & Sietz, M. 1974. Water plants of the world. A manual for the identification of the genera of fresh water macrophytes. W. Junk, the Hague. i - viii, 1 - 561, f. 1 -216.

Copeland, E.B. 1947. Genera filicum, the genera of ferns. Ronald Press, New York. I - xiv, 1 -247, pl. 1- 10.

Copeland, E.B. 1958 - 1960. Fern flora of the Philippines. Vol. 1 - 3. Manila Bureau of Printing. 1 - 555.

Crabbe, J.A., Jermy, A.C. & Mickel, J.T. 1975. A new generic sequence for the pteridophyte herbarium. Brit. Fern Gaz. 11: 141 - 162.

Croft, J.R. 1985. Ferns and Fern Allies, in Leach, G.J. & Osborne, P.L. 1985. Freshwater Plants of Papua New Guinea. 33 - 74, f. 6 - 13, pl. 5 - 7.

Holtumm, R.E. 1954 (revised 1965). Ferns of Malaya. A revised flora of Malaya. Volume 2. 1 -643. Incl. Appendix by I. Manton, Cytological notes on 100 species of Malayan ferns. Govt. Printer, Singapore.

Holtumm, R.E. 1959. 1. Introductory note; 2. List of Malaysian Pteridophytes; 3. The morphology of ferns; 4. General key No 1 to Pteropsida; 5. General key No 2 to Pterspsida; 6. Keys to the genera of Pteropsida; 7. Bibliography. F1. Males. ser. 2 1:I - XXIII.

Johns, R.J. & Bellamy, A. 1979. Ferns and fern allies of Papua New Guinea. P.N.G. Office of Forests. (checklist of genera, treatments of several families; continuing series)

Jones, D.L. & Clemsha, S.C. 1976. Australian ferns and fern allies, with notes on their cultivation. Reed pty ltd, Sydney. 1 - 294, f. 1 - 252, pl. 1 - 60.

Jones, D.L. & Clemsha, S.C. 1981. Ditto. 2nd edition. 1 -232, f. 1 - 297, pl. 1 - 60.

Leach, G.J. & Osborne, P.L. 1985. Freshwater Plants of Papua New Guinea. University of Papua New Guinea Press. 1 - 254, f. 1-59, pl. 1 - 32.

Mitchell, D.S. 1978. Aquatic weeds in Australian inland waters. Aust. Govt. Publ. Service, Canberra. I - xxii, 1 - 189.

Pichi Sermolli, R.E.G. 1970. A provisional catalogue of the family names of living pteridophytes. Webbia 25: 219 - 297.

Pichi Sermolli, R.E.G. 1973. Historical review of the higher classification of the Filicopsida. In Jermy, A.C., Crabb, J.A. & Thomas, B.A. eds., Phyllogeny and classification of the ferns. Supp.. 1 Bot. J. Linn Soc. 67: 11 - 40, f. 1 - 8, pl. 1 -19.

Stanley, T.D. 1979. Aquatic plants of Queensland. Five common free floating aquatics. Advisory Leaflet 1427: 1 - 7. Queensland Div. Plant Industry. (reprinted from Qld. Agric J. 1978.)

Steenis, C.G.G.J. van 1952. Rheophytes. Proc. Roy. Soc. Qld. 62: 61 - 68, pl. 2 - 3.

Steenis, C.G.G.J. van 1981. Rheophytes of the world. An account of the flood-resistant flowering plants and ferns and the theory of autonomous evolution. Sijthoff & Noordhopp, Netherlands.

Willis, J.C. 1973. A dictionary of the flowering plants and ferns. Ed. 8 (edited by H.K. Airy Shaw). Cambridge Univ. Press. I - xxii, 1 - 1245, I - lxvi. (All pteridophyte entries and Introduction to Pteridophyta xiii - xvi by R.E. Holttum)