The orchid comprises one of the largest families of flowering plants, containing as it does over 15,000 species. It is also one of the most widely spread families, for members are found in most parts of the world although the plants themselves are never very numerous in any one place. The peculiar structure of the flowers, designed principally for special insect and sometimes bird fertilisation, makes the family distinctive. Beautiful and grotesque flower development is to be seen especially in tropical species. These have been varied a great deal further by hybridisation, for they are cultivated very widely indeed. Such cultivation is a highly developed art.
In New Zealand there are some 60 species, most of them insignificant in appearance by comparison with many other orchids. Nevertheless, they are noteworthy because they are the representatives of such a large and universal family. The best known is perhaps Dendrobium cunninghamii, found perched on trees throughout lowland forests. It has large, many-flowered racemes of whitish or pinkish flowers, each about three-quarters of an inch across. Earina mucronata is also epiphytic on trees throughout lowland forests and has white, sweet-scented flowers. E. autumnalis is a somewhat similar species, but frequently occurs as a ground plant in beech forest. The most abundant species outside forest areas is Microtis uniflora. It has a single, tubular leaf on a stout stem growing to a height of up to 2 ft above ground level. The single flower spike bears numerous small green flowers. Bulbophyllum pygmaeum is a minute species growing on the trunks of trees. It has a small bulb at the base of each leaf which acts as a water storage organ. This ability to store water is displayed by many orchids, particularly in their root systems. The outer surface of roots is usually spongy. Gastrodia cunninghamii is a curious orchid found in damp bush. It has a thick, starchy root-stock from which a stem, clothed with brown scales, grows about 2 ft high. The flowers are a dirty green, spotted with white, and have an unpleasant smell. Pterostylis is one of the larger New Zealand genera containing about a dozen species or more. They are all terrestial plants with mostly large, greenish flowers possessing boat-shaped hoods. From the lower lip two long, acuminate points jut up. P. banksii is one of the most abundant of New Zealand orchids.
Many of the New Zealand orchids occur also in Australia. Nearly all the genera are found in both countries and about eight genera are confined to them.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.