Achariaceae
Achariaceae contains 30 genera and 145 species of shrubs to trees, or rarely climbing herbs, which are scattered throughout the tropics. The Indo-Malesian Hydnocarpus (40 species) is the largest genus in the family. Ryparosa (18 species) is Malesian, and Lindackeria (14 species) grows in the Americas and Africa. Most species of Achariaceae were previously included in Flacourtiaceae, while Achariaceae in the original sense was a small and little-known family of herbaceous or semishrubby plants from Africa.
Florally, members of Achariaceae are distinctive in that the parts are spiral, not whorled, or if it is whorled, there are more petals than sepals, and the petals have a scale at the base on their inner surface. There are often numerous stamens. The seeds are distinctive because of the vascular bundles clearly visible on their surfaces. The seeds of Hydnocarpus are a source of chaulmoogra oil, at one time important in the treatment of leprosy. The presumed active agent in the oil, hydnocarpic acid, is believed to have antibiotic properties. The seeds of Caloncoba echinata, from west-central Africa, are the source of gorli oil, also used in the treatment of leprosy. (These old treatments for leprosy have been replaced by sulfone drugs and other modern antibiotics.) Achariaceae is chemically quite different from Salicaceae in that many members have cyanogenic compounds of a very distinctive type.
Turneraceae
Members of Turneraceae, a family of 10 genera and 205 species, are found in the tropical and subtropical parts of the Americas, Africa, Madagascar, and the Mascarene Islands. Turnera (122 species) and Piriqueta (44 species) are both found in the Neotropics and Africa. Members of the family often have hairy toothed leaves with strong secondary venation but they lack stipules. In the flowers, the calyx and corolla together form a tube, and the petals overlap regularly and soon become deliquescent after wilting—that is, instead of drying as they wilt, they become soggy. The stigmas are often bifid and fringed. The capsular fruits have arillate seeds with a minutely and often regularly reticulate testa.
Smaller families
Malesherbiaceae contains only Malesherbia (24 species), a genus of herbs and shrubs from often dry regions of western subtropical South America. Members of Malesherbiaceae are fetid and often densely glandular hairy plants with distinctive flowers. The calyx and corolla tube is persistent in fruit. The stamens and ovary are borne on top of a short stalk or androgynophore.
Lacistemataceae is a small family of 2 genera and 14 species native to the tropical and subtropical Americas and the West Indies. Lacistema includes 11 species. The flowers are very reduced and are sometimes borne in almost catkinlike inflorescences.
Goupiaceae is a small family of evergreen trees with two species growing in northeastern South America. The leaves have parallel cross veins, and the inflorescences are umbellate. The petals are long, the apical part being inflexed. The fruit is a drupe.
Erythroxylaceae and Rhizophoraceae
Erythroxylaceae and Rhizophoraceae are very close, having similar distinctive chemistry and cell microstructure.
Erythroxylaceae, or the coca family, contains 4 genera and 240 species of smallish trees to shrubs, which are pantropical but mostly American. The family has entire, mostly alternate leaves without teeth and with stipules that in many species grow between the petiole and the stem. The rather small flowers are in groups in the leaf axils, and both sepals and filaments persist at the base of the fruit. Erythroxylum (230 species) is by far the largest genus in the family and has stamens that are usually joined at the base and of two different lengths. The fruits are fleshy drupes. The dried leaves of E. coca and E. novogranatense are still chewed by Amerindians in western South America, and both are a source of cocaine, which makes it a major (mostly illicit) crop in parts of Colombia, Peru, and Bolivia. A lowland variety of E. coca (ipadu) is cultivated in the Amazon basin of Colombia, Ecuador, Peru, and Brazil. One variety of coca is legally grown in northern Peru and is used as a flavouring for the soft drink Coca-Cola (a name that is derived from the plant). Aneulophus (2 African species, A. africana and A. africanus) is much more like Rhizophoraceae than other Erythroxylaceae.
Rhizophoraceae, or the mangrove family, contains 16 genera and 149 species of trees that grow throughout the tropics. Three small genera, Rhizophora, Kandelia, and Bruguiera, are mangrove plants, and all grow in the Southeast Asia–Malesia area, but Rhizophora alone is pantropical. Cassipourea (62 species), native to Africa, the Americas, and Sri Lanka, Carallia (10 species), native from Madagascar to Australia, and other members of the family grow in tropical forests.
Rhizophoraceae have opposite leaves and large stipules, and they often have aerial roots. The petals are often lobed and hairy or with very narrow appendages. The ovary is more or less inferior. Seeds of the mangrove-dwellers have little endosperm and are viviparous—that is, they germinate precociously while still on the mother plant. The long pointed seedling root dangling from the trees is very characteristic. However, less-specialized Rhizophoraceae have capsular fruits with arillate seeds.
The main importance of the family is ecological, because mangroves form dense vegetation along the coast and in estuaries in the tropics that protects the land from erosion and the effects of tropical storms. The bark of mangrove is used in tanning, and the wood is used for pulp and in building.