Jeffersonia diphylla . Twinleaf is one of only two species in the genus Jeffersonia. Oddly enough, the other lives more than 6,000 miles away in China, Korea and Japan. The genus is one of the few to honor a U.S. president, another being the Washingtonian palm. Thomas Jefferson was considered a naturalist, and the name was selected in his honor by Benjamin Smith Barton (1766-1815), a physician who was also a naturalist, botanist, archaeologist, intellectual, and University of Pennsylvania professor. “Twinleaf” refers not to the fact that it has two leaves, but to the fact that each of its several leaves are deeply divided in two, making each seem like a pair. Possibly the rarest flower in this collection, Twinleaf is protected by laws in at least four states. It favors rich limey woods and can be found high in the mountains bordering the Shenandoah Valley. Earlier Americans knew Twinleaf as Rheumatism Root, so called because it was used to treat the symptoms of that ailment. American Indians have employed the plant for a variety of medicinal purposes, including urinary tract problems, treating sores, and as a tonic. However, like its close cousin, the Mayapple, Twinleaf is poisonous and is better viewed than consumed.