Resins: lipid-soluble mixture of volatile and nonvolatile terpenoid or phenolic secondary compounds. Usually secreted in specialized structures either internally or on the plant surface. Terpenoids: modified terpenes, where methyl groups have been moved or removed, or oxygen atoms added. Terpenoid resins: turpenoids occur in all organisms. Greatest structural and functional diversity in plants. Most diverse class of plant compounds: from the german word for turpentine, structure of approx. Conifer resins: i. e. pinaceae, large volatile fraction (20 50%) Fragrant aroma from xmas trees: inhibits nitrification, supplies energy for forest microbes, defense against insects and pathogens, used to make turpentine. Magnoliophyta resins: common in higher plants, sesquiterpenes are terpenes with 15 carbon atoms, naturally occurring alcohols (evaporate at low temperatures, compounds stimulate glands in the liver; anti-allergen, antispasmodic, and anti-inflammatory properties. Phenolic resins: aromatic ring plus hydroxyl group. Amber: several classifications, two types have potential for fossilization, terpenoids, produced by conifers & angiosperms, phenolic resins, produced by angiosperms.