herbaceous, rarely lithophytes, prostrate or creeping to sub-erect or fully
erect, much branched fern-allies. Rhizome slender, creeping, or scandent,
growing cluster of branches of about the same length. Special rhizophores growing frequently
downwards which bear adventitous roots. Fronds, dimorphic, monomorphic
heteromorphic small simple with microphyllous ligule on the adaxial side at its
base. Vegetative and fertile fronds slightly differentiated and usually
arranged in two median and two lateral rows on the branches. Median lamina
usually smaller and of different shape from the lateral ones. Sporophyll borne in the compact strobili.
Megasporophylls with four megaspores.