Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as cacti. Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance.
Euphorbias range from tiny annual plants to large and long-lived trees. The genus has over or about 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. Euphorbia antiquorum is the type species for the genus Euphorbia. It was first described by Carl Linnaeus in 1753 in Species Plantarum.
The plants share the feature of having a poisonous, milky, white, latex-like sap, and unusual and unique floral structures. The genus may be described by properties of its members' gene sequences, or by the shape and form (morphology) of its heads of flowers. When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and other structures underneath have evolved to attract pollinators with nectar, and with shapes and colors that function in a way petals and other flower parts do in other flowers.
