Euphorbiaceae – Spurge family.
The spurge family is divided into Subfamilies Acalyphoideae, Crotonoideae and Euphorbioideae.
It is one of the largest families of flowering plants with up to 300 genera and 7500 species.
Commonly known as Euphorbias well known genera inlcude Acalypha, Breynia, Codiaeum, Croton,
Euphorbia, Jatropha, Macaranga, Phyllanthus, Poinsettia and Ricinus.
Many contain toxins.
Most are annual or perennial herbs but there are some trees and shrubs.
About 12 % are cactus-like succulents and many have a milky sap.
Leaves are mostly alternate and spirally arranged, rarely opposite or whorled.
Most are simple but some are palmately divided.
Some are succulent and some are reduced to spines or scales.
In a few genera the leaves are replaced by photosynthetic petioles or stems.
There are usually leaf-like stipules but they can be reduced to glands, spines or hairs.
Flowers are unisexual, usually with male and female on the same plant but sometimes on separate plants.
With such a large family there are great variations among the inflorescences and flowers.
Inflorescences are terminal or axillary.
Usually either the calyx or corolla is missing and sometimes neither are present.
When present there are 5 or 6 (3 – 12) sepals &/or petals that are mostly sepal-like.
The parts can be free or joined.
There is often a hypogynous (nectiferous) disc.
There are often 5 or 10 stamens – equal to the perianth parts or 1 to many.
The filaments can be free or variously fused but are free of the perianth.
Anthers mostly open via longitudinal slits.
The superior ovary typically consists of 3 (1 – 20) fused carpels.
Each of the 3 locules has 1 or 2 ovules with axile placentation.
There are 3 styles (free or variously joined) that may branch once or more.
The fruit take various forms.
Plants in the Euphorbia genus have a particular type inflorescence called a cyathium.
Each cyathium, made up of several greatly reduced flowers, resembles a single flower.
The united bracts form a cup-like ‘perianth’ or involucre which holds the nectaries.
Inside this is a ring of male flowers each reduced to one stamen on a stalk.
In the centre is one female flower reduced to one stalked carpel with a branched stigma.
J.F.
