They are found in the Compoeitae (Cickoriaceae), Campanulaceae, Papaveraceae, Loheliaceae, Papayaceae, in some Aroideae and Musaceae, and in Euphorbiaceae (Manihot, Ilevea).
Cactaceae, Euphorbiaceae), of parasites, and of saprophytes.
Amongst arboreous families Leguminosae and Euphorbiaceae are prominent; Hevea belonging to the latter is widely distributed in various species in the Amazon basin, and yields Para and other kinds of rubber.
The principal orders, arranged according to their numerical importance, are as follows: - Leguminosae,Rubiaceae, Orchidaceae, Compositae, Gramineae, Euphorbiaceae, Acanthaceae, Cyperaceae and Labiatae.
Euphorbiaceae and Scrophulariaceae and Orchidaceae are universally present, the last in specially large proportions.
The more common plants in the most characteristic part of this region in southern Arabia are Capparidaceae, Euphorbiaceae, and a few Leguminosae, a Reseda and Dipterygium; palms, Polygonaceae, ferns, and other cryptogams, are rare.
The trees and plants whose latices furnish caoutchouc in considerable quantity chiefly belong to the natural orders Euphorbiaceae, Urticaceae, Apocynaceae, Asclepiadaceae.
Manihot Glaziovii belonging to the Euphorbiaceae is the tree of N.E.
In Coelebogyne (Euphorbiaceae) and in Funkia (Liliaceae) polyembryony results from an adventitious production of embryos from the cells of the nucellus around the top of the embryo-sac. In a species of Allium, embryos have been found developing in the same individual from the egg-cell, synergids, antipodal cells and cells of the nucellus.
The similarity of certain xerophilous Euphorbiaceae to Cactaceae is a ready illustration of this phenomenon.
Of these, the orders most largely represented (together with their species) are: Leguminosae, 34 6; Filices, 318; Compositae, 281; Euphorbiaceae, 228; Orchideae, 170; Cyperaceae, 160; Rubiaceae, 1 47; Acanthaceae, 131; Gramineae, 130.
In the Euphorbiaceae we have an excellent example of the gradual suppression of parts, where from an apetalous, trimerous, staminal flower we pass to one where one of the stamens is suppressed, and then to forms where two of them are wanting.
The plants of which the floral organs or perfect fruits are preserved include the amber-bearing Pinus succinifera, Smilax, Phoenix, the spike of an aroid, i i species of oak, 2 of chestnut, a beech, Urticaceae, 2 cinnamons and Trianthera among the Lauraceae, representatives of the Cistaceae, Ternstroemiaceae, Dilleniaceae (3 species of Hibbertia), Geraniaceae (Geranium and Erodium), Oxalidaceae, Acer, Celastraceae, Olacaceae, Pittosporaceae, Ilex (2 species), Euphorbiaceae, Umbelliferae (Chaerophyllum), Saxifragaceae (3 genera), Hamamelidaceae, Rosaceae, Connaraceae, Ericaceae (Andromeda and Clethra), Myrsinaceae (3 species), Rubiaceae, Sambucus (2 species), Santalaceae, Loranthaceae (3 species).