Rhizomatous, spore-bearing vascular plant 2-3 feet tall, native to southeastern United States, Japan and Australia. This genus is one of only two genera in the whole phylum psilotophyta. Whisk Fern has very primitive morphology. It best represents what some of the first vascular land plants in the Devonian would have look like. It has only dichotomously branching stems, sporangia, and leaf-like enations. In that respect it resembles the other Devonian vascular plants as Rhynia and Cooksonia. There are some, however, who think it is a specialized fern-ally.

Recent molecular evidence suggests, however, that Psilotum is not as primitive as most people believed and is related to ferns.