Tribalism in the Family Euphorbiaceae

A short history of the tribal arrangement in the vast family Euphorbiaceae has been given by Henri Baillon in France, Jean Müller of Argau in Switzerland, George Bentham in England, and Ferdinand Pax in Germany. Speculation follows on the ancestors of the group, considered to be polyphyletic and probably derived from more primitive orders with hypogynous flowers, such as Tiliales and Malvales, Celastrales, and Rhamnales, all of which are fundamentally woody, as are most of the Euphorbiaceae. Considered to be ancient characters are the presence of petals, the lack of a disk, the retention of a vestigial ovary in the male flowers, numerous stamens, and the imbrication of the sepals. The sequence of the tribes is based on these assumptions, culminating in the most advanced, such as H ureae , D alechampieae , P ereae , R icineae , C rotoneae , J oannesieae , ending with the most advanced of all, the E uphorbieae. A dichotomous key to the tribes and their descriptions is provided, usually listing only the principal genera with the approximate number of species (in parentheses). A more detailed account will be published in the author's third volume of The Genera of Flowering Plants. Twenty of the tribes are illustrated by drawings by the author of representative genera.