Birthwort

Birthwort, common name for a small family of flowering plants that are usually woody vines with medium to large, luridly coloured, ill-smelling flowers. The family contains seven genera and about 625 species which occur in tropical and temperate areas, excluding Australia. The family is of little economic importance, although local medicinal use occurs; some members are grown as curiosities.

The shape, colour, and smell of the flowers all reflect adaptations to pollination by insects, particularly carrion flies. These insects are attracted to the flowers by their scent, which often resembles that of rotting meat, by their coloration, usually darker shades of red or purple mottled with lighter colours, and in some species by the generation of heat in the flower. The flower is expanded above and tubular below. The female parts of the flower (pistil) cover the male parts (anthers) and mature before them. After entering the tube of the flower, the insects cannot escape because of stiff downward-pointing hairs that line it. If the insect has brought pollen from another flower and pollination occurs, then the anthers open, loading the insect with a fresh supply of pollen, and the next day the hairs relax, allowing the insect to escape. Petals are absent from most members of the family, the floral tube and showy perianth being formed from the calyx. Another unusual feature of the family is that the flower parts are in multiples of three, more typical of monocotyledons (see Monocots), rather than in the fours or fives typical of dicotyledons (see Dicots). Other characteristics, however, show that birthworts are dicots.

The two largest genera in the family are Aristolochia, with about 500 species, and Asarums, with about 100 species. Various species of Aristolochia, such as Dutchman's pipe, are cultivated as climbing plants. The pelican flower from Jamaica has a tail of almost 1 m (3 ft) on the expanded perianth. In the genus Asarum, asarabacca and wild ginger are used as medicinal plants in Europe and North America respectively.

Scientific classification: Birthwort is the common name for the family Aristolochiaceae. Dutchman's pipe is classified as Aristolochia durior, pelican flower as Aristolochia grandiflora, asarabacca as Asarum europaeum, and wild ginger as Asarum canadense.