Pteris (brake) is a genus of about 280 species of ferns in the Pteridoideae subfamily of the Pteridaceae. They are native to tropical and subtropical regions of the world. Many of them have linear frond segments, and some have sub-palmate division. Like other members of the Pteridaceae, the frond margin is reflexed over the marginal sori. The outermost layer is the single-layered epidermis without stomata. The cortex is differentiated into outer and inner cortical region . The vascular cylinder is amphiphloic siphonostele The term "brake", used for members of this genus, is a Middle English word for "fern" from southern England. Its derivation is unclear, and is generally thought to be related to "bracken", whereby the latter word has been assumed to be a plural, as with "children", and the former word a back-formation. However it may have a separate derivation.