Order LXXIX. ORCHIDEÆ.
Herbs, either terrestrial and tuberous-rooted, with annual herbaceous stems; or epiphytes with creeping rhizomes emitting fibrous or fleshy roots and bearing simple or branched leafy stems often thickened into pseudobulbs. Flowers hermaphrodite, solitary or in spikes or racemes or panicles, often large and showy. Perianth superior, irregular, of 6 free or more or less combined segments, in 2 series; the 3 outer (sepals) all similar or the dorsal one larger and more concave than the 2 lateral which are always alike; the 3 inner (petals) always dissimilar (except in Thelymitra), the 2 lateral alike, but the third (called the lip, or labellum) usually exceedingly different, often spurred, lobed, fringed, or furnished with glands or other appendages. Stamens and style confluent into a fleshy variously shaped central body facing the lip, called the column; anther usually solitary (2 in Cypripedium), placed on the front, top, or back of the column, and either free or adnate to it, persistent or deciduous, usually 2-celled; pollen granular or waxy, usually cohering in each cell into 1, 2, or 4 pairs of pollen-masses (pollinia), which are either free or attached, directly or by a caudicle, to a gland on the apex of the stigma (rostellum). Ovary inferior, 1-celled; ovules numerous, on 3 parietal placentas; stigma a viscid depression towards the top or on the front of the column, below the anther, facing the lip, upper margin often produced into a beak or point called the rostellum. Fruit a 1-celled 3-valved capsule; seeds numerous, very minute; testa loose, reticulate; albumen wanting; embryo solid, fleshy.
A very extensive and distinct family, found in almost all parts of the world, but rare or absent in extreme northern or southern latitudes, and on the tops of high alpine mountains. Most of the species found in temperate countries are terrestrial; but in the tropics the greater number are epiphytes, growing upon the branches or trunks of trees or on rocks. The genera are estimated at 340, the species at 5000. Notwithstanding the great extent of the order, it is singularly deficient in useful plants. The only one possessing any commercial importance is vanilla, the scented pods of which are used for flavouring delicate dishes or liqueurs. The great beauty and singularity of the flowers of many of the tropical species have caused them to be extensively cultivated in hothouses, and probably over 2000 distinct species are now grown by European horticulturists.
The close affinity existing between the flora of New Zealand and that of Australia is nowhere better shown than in the Orchideæ. Out of 21 genera found in New Zealand, 19 occur in Australia as well, and 8 are absolutely confined to the two countries, while several others have a very limited additional range. The only genera with a wide distribution are Dendrobium, Bulbophyllum, and Spiranthes. Earina, which does not occur in Australia, is found in the Pacific islands, while Townsonia is endemic.
| A. Epiphytes with creeping rhizomes, perennial stems, and evergreen leaves. Pollinia waxy, free or attached by caudicles to the rostellum. | |
| * Pollinia free. | |
| The New Zealand species with slender much-branched stems, no pseudobulbs and axillary flowers. Lateral sepals and lip adnate to the base of the column | 1. Dendrobium. |
