The North American "Jacks-in-thePulpits" are so variable as to have caused a great deal of controversy and confusion. Six specific and numerous subspecific epithets have been applied to them. Graduate research at Cornell between 1946 and 1950 and extensive observations since have lead me to the conclusion that there is but one species, Arisaema triphyllum (L.) Schott, with four subspecific populations. Rather widespread hybrid swarms between these populations tend to confuse their separations. A key to the subspecific categories and a discussion of them follows.