Nota de aplicación
Group consisting of two extant genera, Psilotum and Tmesipteris. They are chiefly tropical, clump-forming plants of skeletal appearance resembling whisk brooms. These plants are primitive in structure, lacking both roots and leaves, or having structures on the aerial shoot that are foliar. They are structurally similar to the fossil genus Rhynia. Recent molecular systematic studies suggest that the family is actually related to primitive ferns.