The oil is thought to preserve iron and repel termites. Burma, Malabar, Rangoon, and other teaks take names from districts producing them. The distinct African teak (_Oldfieldia africana_) affords wood sometimes marketed as African mahogany and sometimes as African oak. (Forestry methods, see "Burma Teak Forests," Sir Dietrich Brandis, "Garden and Forest," Vol. IX, "Forestry and Irrigation," Vol. IX, No. 3, p. 139.) [p117] GREENHEART. _Nectandra rodiali._ Nomenclature. Greenheart (local and common name). Locality. British Guiana and adjacent portions of South America and the West Indies. Features of Tree. Twenty-five to sometimes seventy feet in height, two to four feet in diameter. A straight tree. Color, Appearance, or Grain of Wood. Heartwood dark green to chestnut or nearly black, sapwood similar. Clean, straight, compact structure, free from knots. Numerous pores, annual layers hardly distinguishable. Structural Qualities of Wood. Exceptionally heavy, strong, and durable, tough, hard, elastic, receives high polish, breaks suddenly. Representative Uses of Wood. Ship-keels, frames, rollers, turnery, also beams, planks, and piles (Europe). In America tops of fishing-rods and very occasionally veneers. Weight of Seasoned Wood in Pounds per Cubic Foot. 72 (Lazlett). Modulus of Elasticity. 1,090,000 (Lazlett). Modulus of Rupture. 10,000 (Thurston). Remarks. Excessive weight unfits it for many purposes. Placed in first class of ship-building woods by Lloyd's Register. Formerly supposed to repel teredo. Generally exported through Demerara to England. [p118] MAHOGANY. (_Swietenia, Khaya, Soymida, Cedrela, etc._) There are three principal mahogany trees: the Central American or true mahogany (_Swietenia mahogani_), the African mahogany (_Khaya senegalensis_), and the Indian mahogany (_Soymida febrifuga_). There are also minor species called mahoganies.[61] American mahogany was originally divided by dealers into Spanish and Honduras wood, the former from the then Spanish-American possessions. A considerable supply now comes from Mexico, taking name from port of shipment; as, Frontera, Laguna, Santa Ana, Tecolutla, Minatitlan, and Tonala, desirability being much in the order named. The African field is the latest and probably most important, very large quantities of its wood being distributed through English markets. [Illustration: PLATE 25. MAHOGANY (_Swietenia mahagoni_). Two Specimens of Wood.]