Loganiaceae
A natural order of herbs, shrubs, or trees, of variable habit, closely allied to Rubiaceae. They inhabit chiefly warm and tropical countries. Flowers often red, white, purplish, or pale citron, rarely yellow, axillary and solitary, or racemose or corymbose, sometimes in a terminal corymb or panicle. Leaves opposite, stipulate, or exstipulate when the dilated and connate bases of the petioles embrace the stem, with a short, sometimes obsolete border. Stem woody, rarely herbaceous. Most Loganiaceae have a very bitter juice. The species of strychnos contain in the bark of their root, and in their seeds, two alkaloids, combined with a peculiar acid, the principles which are extremely energetic; their action on the nervous system is very powerful. There are about thirty genera and 350 species. Examples: Gaertnera, Logania, Spigelia, Strychnos.