Aristolochia, in family Aristolochiaceae has around 450 species.
Other figures seen are around 120, 200, 300, 500 and 540.
The variation depends on which other genera, such as Pararistolochia are included.
Australia has 1 genus with 8 species including 4 in south-eastern Queensland.
Being the largest genus means that family and genus descriptions are similar.
There are some shrubs but most are perennial twining or scrambling vines.
Some have rhizomes with tubers while others have fibrous roots.
New stems may be smooth or have rust-coloured hairs.
Leaves, alternately arranged in 2 ranks are on thick twisted petioles.
From the petiole base a ridge extends around the stem.
Leaves from undeveloped axillary buds may form pseudostipules.
Blades may be entire or have 3 to 7 lobes each with a prominent midvein.
Blade bases are commonly heart-shaped (cordate).
Axillary or leaf-opposed inflorescences are a solitary flower, cluster or raceme.
Racemes are a spike with flowers, on a pedicel that open from the base first.
The racemes only have a few flowers.
The bilaterally symmetric flowers usually emit a smell of rotting flesh.
There are no petals but a calyx that is coloured like a petal.
The narrow straight or curved tube is swollen at the base.
It expands at the top with 0 or 3 to 6 lobes on the rim.
There are hairs inside the throat and smaller ones in the swollen base.
The 6 or more stamens are just an anther fused to the stigma lobes.
The inferior ovary has 6 locules and a short style with 3 to 6 stigmatic lobes.
Some fruit are a capsule, opening from the base up into the 6 chambers.
Others are fleshy, orange or yellow with 6 ribs.
The numerous flattened seeds in each chamber have a thickened edge or wing.
The native species are food for some Richmond Birdwing Butterfly larvae.
J.F.
