Free living primitive plants which reproduce by means of spores instead of flowers and seeds. Mostly all perennial due to underground stock; usually solenostelic rhizomes with opaque scales. Spore producing organs (=Sporophytes) have vascular tissue and are borne under the leaves. Fertile and sterile leaves are somehow different. The tiny (powder-like) spores produced by the sporangia give rise to filamentous or thalloid gametophytes called prothalli which develop to form new plants. Plants have petioles with 2 vascular strands. The sporangia are arranged in a series of rows along the veins and not in well-defined sori. Soral induism absent. Spores tetrahedral shape.
