Classification of Some of the Plants of Australia:
A Brief Introduction

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Notes by
Dr. Elizabeth Newell
Department of Biology
Hobart and William Smith Colleges

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Classification

Photosynthetic organisms range from prokaryotes to complex, long-lived flowering plants. They are found in the kingdoms Eubacteria (prokaryotes), Protista (algae), and Plantae. In the classification of plants, the term "division" replaces "phylum." Thus, the categories of classification are: Kingdom, Division, Class, Order, Family, Genus, Species.

Within the kingdom Plantae, divisions are grouped into the following categories (listed from most ancient to most recently evolved):

Non-vascular plants - no true vascular system (xylem, phloem), no true leaves, stems, roots; alternation of generations with the haploid gametophyte stage dominant.

Vascular plants - true xylem and phloem; leaves, stems, roots, alternation of generation with diploid sporophyte stage dominant.

• Non-seed plants - dispersal is through spores; fertilization requires water; tiny, but independent haploid gametophyte stage.
• Seed plants - dispersal is through seeds; fertilization occurs through pollination and water is not required; gametophyte stage is much reduced and depends on sporophyte for nourishment.
  • Gymnosperms ("naked" seed plants) - non-flowering plants that don't produce fruit.
  • Angiosperms ("vessel" seed plants) - flowering plants, ovary walls develop into fruits.

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Classification of a Few Australian Plants

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1. Kingdom Protista

• Division Pyrrhophyta (Dinoflagellates)

  • Zooxanthellae - the symbiotic form of dinoflagellates. Living within the tissues of corals, sponges, jellyfish, sea anemones, tunicates, octopuses, and squids, these photosynthetic dinoflagellates provide their hosts with an energy source. Coral tissues may contain as many as 30,000 symbiotic dinoflagellates per cubic millimeter! The distribution of corals containing zooxanthellae is limited to water depths with sufficient light.

• Division Phaeophyta (Brown algae)

  • Sargassum spp. - this brown "seaweed" can be found floating in masses as well as attached to the bottom. The brown color comes from secondary photosynthetic pigments such as fucoxanthin. Air-filled bladders help keep plants afloat or upright in the water. Diploid life cycle.

• Division Chlorophyta (Green algae)

  • Chlorodesmis fastigiata - turtle weed.

2. Kingdom Plantae

A. Non-vascular Plants

• Divisions Bryophyta, Hepatophyta, Anthocerophyta: Mosses, Liverworts, and Hornworts

B. Vascular, Non-seed Plants

• Division Psilophyta

  Only two genera (Psilotum and Tmesipteris). Tmesipteris is found only in Australia and the South Pacific. It grows as an epiphyte on tree ferns and other plants.

• Division Lycophyta (Club Mosses)

• Division Sphenophyta (Horsetails)

• Division Pterophyta (Ferns)

  • Asplenium spp. - Bird's nest ferns.
  • Platycerium spp. - Staghorn ferns.
  • Polypodium spp. - Elkhorn ferns.

C. Gymnosperms ("Naked Seed" Plants)

• Division Cycadophyta

  Leathery fern-like leaves radiate from a central trunk or stalk. Pollen and seeds are produced on separate male and female plants. Insects are important pollinators.
  • Cycadaceae (Cycad Family)
    • Macrozamia sp.

• Division Ginkgophyta

  Only one living species: Ginkgo biloba, a tree.

• Division Gnetophyta

  Three living genera: Gnetum, Ephedra, and Welwitschia.

• Division Coniferophyta (Conifers)

  • Araucariaceae (Araucaria Family) - includes the popular Norfolk Island Pine.
    • Araucaria cunninghamii - Hoop pine.
    • A. bidwillii - Bunya pine.

D. Angiosperms (Flowering Plants)

• Division Anthophyta

  Class Dicotyledones

  Dicots -- embryo with 2 cotyledons; flower parts usually in fours or fives, leaf venation usually net-like, true secondary growth present, i.e., trunk thickening, as in woody plants.
  • Casuarinaceae (She Oak and River Oak Family) - represented by only one genus; natural distribution limited to SE Asia and the SW Pacific but now planted around the world.
    • Casuarina spp. - tall trees with "weeping" appearance caused by their jointed branches. Leaves are almost needle-like and look like horsetails. Flowers are very small with separate male and female flowers on the same plant.

  • Convolvulaceae (Morning Glory Family) - widespread distribution
    • Ipomoea sp. - often with long-twining stems, characteristic of rich bushy, vegetation or open, drier places, including sand dunes.

  • Droseraceae (Sundew Family) - cosmopolitan family of carnivorous plants divided into 4 genera; includes venus' fly traps.
    • Drosera spp. (Sundews) - Upper surface of leaves covered with hairs and glands that trap and digest insects.

  • Fabaceae (Legume or Pea Family) - cosmopolitan distribution, herbs, shrubs, and trees
    • Acacia - a genus with LOTS of species, including:
    • A. pycnantha - Golden wattle.
    • A. fimbriata - Brisbane wattle.

  • Fagaceae (Beech Family) - temperate to tropical hardwood trees; includes oaks and sweet chestnuts, as well as beeches.
    • Nothofagus moorei - Antarctic beech.

  • Moraceae (Fig Family) - trees and shrubs; distribution is centered in the tropics and subtropics; produce latex-containing milky sap.
    • Ficus spp. - Figs.

  • Myrtaceae (Myrtle Family) - mostly shrubs and trees, generally tropical or subtropical in their natural distribution; yield spices and oils such as cloves, allspice, bay rum, and eucalyptus oil.
    • Eucalyptus spp. Most important genus of Australian forest trees, with over 500 species. Some people divide the species into 3 main groups: 1) those found in northern areas with summer rainfall, 2) those found in southern areas with winter rainfall, and 3) those in the southwest of Australia. Great variation in form. Leaves are typically heterophyllous -- with different types of leaves produced at different stages of plant maturity. Seedling leaves are roundish and clasp the stem (used frequently in floral arrangements) while leaves on adults are very long and narrow with a distinct petiole. Fruits are woody and split open to release the seeds.
    • Leptospermum spp. - tea trees.
    • Melaleuca spp. Approx. 150 species, most with papery bark.
    • Lophostemon confertus - brushbox.

  • Portulacaceae (Portulaca Family) - annual and perennial succulent herbs and subshrubs; leaves are fleshy.
    • Portulaca oleracea - Pigface

  • Proteaceae (Protea Family) - one of the most prominent families of the southern hemisphere. Plants often found in regions with long dry seasons. Flowers are usually in showy inflorescences.
    • Banksia spp. - inflorescences often have up to 1,000 flowers.
    • Grevillea spp. - only 3 species: one native to Chile, two native to Queensland and New Guinea. Used for timber.

  • Rhizophoraceae (Mangrove Family) - tropical family found in rain forests and mangroves. Extremely important plants along tropical coasts.
    • Avicennia marina - grey mangrove.

  • Urticaceae (Stinging Nettles and Ramie Fiber) - family is found in most temperate and tropical regions, although relatively poorly represented in Australia.
    • Dendrocnide excelsa - stinging tree.

  Class Monocotyledones

  Monocots -- embryo with one cotyledon; flower parts usually in threes, leaf venation usually parallel, no true secondary growth, no thickening of woody stems.
  • Aracaceae (Palm Family) - chiefly tropical in distribution; main stem has no secondary thickening nor branching.
    • Archontophoenix cunninghamiana

  • Orchidaceae (Orchid Family) - over 18,000 species distributed worldwide. Seeds are extremely small and produced from intricate flowers with bilateral symmetry. Pollination is by insects and some amazing plant-pollinator relationships have evolved in this family.
    • Dendrobium speciosum - King orchid.
    • D. Falcorostrum - Beech orchid.
    • D. bigibbum - Cooktown orchid.

  • Pandanaceae (Screw Palm Family) - a large family of tropical trees, shrubs, and climbers. Distribution is in the Old World tropics and subtropics. Not true palms. Stems bear annual scars of leaf bases. Inflorescence is a spadix. Fruits look something like pineapples.
    • Pandanus tectoris - Screw palm.

  • Poaceae (Grass Family) - about 9,000 species, cosmopolitan distribution; fruit a grain.
    • Imperata cylindrica - Blady grass.
    • Themeda triandra - Kangaroo grass.
    • Spinifex sericeus - Beach spinifex.

  • Xanthorrhoeaceae (Grass Tree Family) - distribution limited to Australia and South Pacific. These are stout, woody perennials, often with tall, few-branched stems. Many are xerophytes.
    • Xanthorrhoea sp. - grass tree.