Diversity:  perennial herbs, often epiphytic (tropics) and sometimes terrestrial (temperate) with floral adaptations similar to those of the Asclepidaceae of the Asteridae.  The largest monocot family and possibly the largest flowering plant family with over 1,000 genera and over 20,000 species including many ornamental domesticates and also the spice vanilla (Vanilla planifolia).

Distribution:  Worldwide and mostly pantropical with many temperate extensions. The Texas flora includes 16 genera and 46 species with a single endemic species that is also endangered (see North American taxa).

Floral structure:

gynoecium/androecium adnation - androecium reduced

Significant features:  Similar to families of the Liliales, i.e., perennial herbs with linear, 'monocot-like' leaves and various shoot features of the herbaceous perennial (bud, rhizome, corm, etc.).  Orchids are, however, often epiphytic with conspicuous adventitious roots.  Like the Ericaceae, this family has a strong association with fungi, mycorrhizal root associations and fungal assistance with seedling development. Zygomorphy is usually produced by the a single modified petal or labellum and, like the Asclepidaceae, the center of the flower is occuplied by a single structure (column or gynandrium) representing fusion of the gynoecium and androecium.  The anther contents are also massed in this family to produce pollen 'packages' or pollinia for vector transfer.  This diverse family produces the smallest angiosperms seeds, reduced to an undifferentiated embryo as a adaptation for wind dispersal to epiphytic safe sites.
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plant	flower - with labellum, sepals, upper 2 petals

calyx green	pollinia removed from the column

More information on the Orchidaceae