The crown of thorns belongs to the genus Euphorbia, which contains nearly 2,000 species, and is characterised by a specialised inflorescence, called the ‘cyathium’ (10) (11). The cyathium of the crown of thorns is made up of cup-like whorls of the brightly coloured (usually red), modified leaves, known as bracts, which enclose several male flowers and a single, female flower. The flowers are unusually simple, with the male flowers reduced to single stamens and the female flower composed of an ovary and greatly reduced perianth (7) (10). The flowers are pollinated by flies (from the genus Diptera), which are attracted to the plant by nectar-producing glands on the cyathium (7).
Another characteristic feature of all Euphorbia species, including the crown of the thorns, is the presence of milky latex, or sap, which is secreted by the plant though broken stems, or damaged roots and leaves. Found in all parts of the plant, the latex is usually poisonous and probably developed in order to protect the plant from herbivores (4). Ingestion of the plant is known to cause severe irritation of the mouth and digestive systems, and may induce nausea, diarrhoea and swelling, while direct contact with the sap causes skin irritation, inflammation and blistering (4) (5) (7) (10) (11).