Some are cultivated as ornamental plants, such as "Guaiacum", "Zygophyllum", "Tribulus", and "Larrea" species. The trade of all species of "Guaiacum" is controlled under CITES Appendix II. They are close relatives of the "true" "lignum vitae" trees of genus "Guaiacum". Gum guaicum, or guaiac resin, is a substance produced from the tree species "Guaiacum officinale". Some physicians continued to use both mercury and guaiacum on patients. In this case the Lignum vitae is from the "Guaiacum officinale" tree. "Guaiacum officinale" is the national flower of Jamaica. The national flower of Jamaica is the lignum vitae ("Guaiacum officinale"). "Guaiacum sanctum" is the national tree of the Bahamas. The Spanish encountered guaiacum wood when they conquered San Domingo in the sixteenth century. Guaiacum angustifolium is a species of flowering plant in the caltrop family, Zygophyllaceae. Dry limestone forest species include "Pisonia albida", "Guaiacum sanctum", and "Plumeria alba". As a food additive, "Guaiacum" is designated E314 and classified as an antioxidant.