Phyllanthaceae and Picrodendraceae
The Phyllanthaceae and Picrodendraceae families, which were formerly associated with Euphorbiaceae, share explosive capsules, with two ovules per chamber.
Phyllanthaceae
Phyllanthaceae contains 59 genera and more than 1,700 species of herbs to trees that grow in tropical to warm temperate regions; the family is especially diverse in Malesia. Members of Phyllanthaceae have often finely cracking bark and two-ranked leaves that lack glands. The fruits have two seeds in each chamber. The pantropical Phyllanthus (about 1,300 species, including the former genera Glochidion, Breynia, and Sauropus) has simple leaves that often look as if they are leaflets of a compound leaf. Glochidion (about 300 species) is tropical, excluding mainland Africa, and species are particularly common in Indo-Malesia. Sauropus (70 species) grows from Indo-Malesia to Australia. Antidesma (100 species) is native to the Paleotropics and warm temperate regions. Cleistanthus (140 species) is native to the Paleotropics. Baccaurea (50 species) grows from Indo-Malesia to the western Pacific. Aporosa (90 species) is native to Indo-Malesia. Bridelia (50 species) grows throughout the Paleotropics. Uapaca (60 species) is found in Africa and Madagascar.
Picrodendraceae
Picrodendraceae includes 80 species in 24 genera. The family is tropical, with genera especially common in the region of New Guinea, Australia, and New Caledonia, and species can be found in the Americas, Africa, and Madagascar. The species in the family are rather undistinguished-looking plants, with small flowers that lack any distinction between sepals and petals and often opposite leaves that are toothed and pinnately veined, with stipules. Their seeds often have a little fleshy appendage at one end that is involved in dispersal.
Ungrouped families
There are several unplaced families in Malpighiales. Members of Caryocaraceae are evergreen trees to shrubs whose leaves have three leaflets and basal stipules. The large flowers are borne in racemes at the ends of the branches and have many long, spreading stamens; the petals are relatively inconspicuous. The seedling root is spirally twisted. The family contains 2 genera, Anthodiscus (15 species) and Caryocar (6 species), which are found in the Neotropics, especially in Amazonia. Some fruits of Caryocar are used as fish poisons. In South America they are the source of edible souari nuts, which are both collected in the wild (C. nuciferum) and cultivated (C. amygdaliferum).
Ctenolophonaceae includes a single genus, Ctenolophon, with three species from West Africa and Malesia. They may be recognized by their opposite toothless leaves, and there are stipules between the petioles. The inflorescences are terminal, and the flower buds are rather elongated. The petals overlap regularly. The gray-drying and closely ribbed fruit is distinctive; the rounded sepals persist, even growing somewhat after flowering.
Humiriaceae includes 8 genera and about 50 species of evergreen trees. Most, including Vantanea (16 species), Humiriastrum (12 species), and Humiria (4 species), grow in the Neotropics, but Saccoglottis (8 species) also grows in West Africa. The flowers are rather small but distinctive. The stamens are more or less fused in a tube and have prolongations at their apices. The fruit is a one- or two-seeded drupe with a ridged stone. The wood of Humiria, in particular, can become beautifully scented after it is attacked by fungi, and then it can be used as incense. The fruit is sometimes edible.
Linaceae, or the flax family, contains 10 to 12 genera and about 300 species of herbs to trees or lianas with curved grapnels and fruits with only a few seeds. The family is found worldwide but especially in north temperate and subtropical regions. Linum (180 species) is a temperate to subtropical genus. Linum usitatissimum (flax) yields fibres and linseed oil, a drying oil. Although Linum is a familiar plant, the relationships of the family, and indeed its basic morphology, are not well understood.
Peridiscaceae consists of three small genera of the tropics: Peridiscus is found in Amazonian Brazil and Venezuela; Whittonia is restricted to Guyana in northeastern South America; and Soyauxia is native to West Africa.
Irvingiaceae contains 3 genera and 10 species of tropical trees found in Africa and from Southeast Asia to western Malesia. The leaves are rather distinctive with their longitudinal markings, large deciduous stipules that enclose the prominent pointed terminal bud, and closely parallel secondary venation. The thin sepals persist in fruit and are conspicuously reflexed, and the nectary disc is very obvious. The species in the family used to be included in the tree of heaven family, Simaroubaceae.
Pandaceae contains 3 genera and 15 species of trees to shrubs, growing from Africa to New Guinea. Microdesmis (10 species) grows almost throughout the range of the family. The branches often look like compound leaves, and the male and female flowers are small and borne on separate plants. The fruit is a drupe.
Ixonanthaceae contains 4 or 5 genera and 21 species of trees scattered throughout the tropics.
Centroplacaceae contains just one genus with one species, Centroplacus glaucinus, from West Africa.
Paul E. Berry