Family Rutaceae.
Commonly known as the Citrus family it is divided into 3 (Mabberley) or 7 (Engler) subfamilies but more work needs to be done on defining these.
There are about 160 genera (150 – 170) and 1600 species (900 – 1975).
A wide range of species are found in Australia including Citrus (oranges, limes etc.), Murraya, Diosma, Flindersia and Melicope.
All members have aromatic leaves with oil glands seen as transparent or translucent dots.
Most are large evergreen trees or shrubs with a few herbs.
Some have thorns or spines and the stems are dotted with glands.
Leaves can be alternate (spirally arranged) or opposite.
Most have petioles (sometimes winged) but some have none or a very short one.
The blades are often compound but can be simple.
Compound leaves includes trifoliate, pinnate or palmate.
The edges can be smooth or have small teeth.
The oil glands may be over the whole blade or just around the margins.
Pores (for gas exchange) may be on one or both surfaces.
There may be hairs, sometimes with glands.
Terminal or axillary inflorescences may be a solitary flower to variously branched clusters.
The bisexual (rarely unisexual) flowers mostly have parts in 4’s or 5’s.
They are on stalks and there are no bracts.
The 4 or 5 (3) sepals and petals may be free or have their bases joined.
Flowers are often white or cream but can be other colours such as reds and pinks.
Stamen numbers are mostly equal to, or twice the number of the petals (3 to 60).
Mostly free but when numerous they may be joined in bunches.
In 1 or 2 whorls they can be branched or unbranched or have a (hairy) appendage.
They may be equal or unequal and are sometimes joined to the corolla.
Anthers are dorsi- or basifixed and open inwards (or laterally) via slits.
All stamens may be fertile or some reduced to infertile staminodes.
There is usually a hypogynous or nectiferous disc inside the stamens.
It can be a complete or partial ring or separate lobes.
There may be an androphore or gynophore.
Male flowers have a rudimentary ovary.
Almost all genera have a superior ovary.
There are mostly 4 – 5 carpels (1 – many).
Carpels may be fully free or united, or joined at the base or sides.
When the ovaries are free the styles may be joined.
Each locule may have 1 to many ovules with parietal or axile placentation.
There is usually only 1 large stigma.
Fruit are variable and include berries, drupes, capsules and follicles.
Others are hesperida (berry-like with a rough skin e.g. citrus), samaras (dry, indehiscent and winged) or schizocarps (dry, indehiscent and break into individual carpels or mericarps).
There are 1 to many seeds per carpel variously shaped and sometimes winged.
J.F.
