A study of these three fern-genera has been undertaken for Flora Malesiana. Teratophyllum and Lomagramma have their main distribution in Malesia; Lomariopsis is pantropic. All three have a distribution extending to the Society and Austral Islands and to New Caledonia; all three are almost confined to the tropics, and all are found only in welldeveloped evergreen forest, so that in the Pacific they only occur on islands large enough to develop such forest. Only Teratophyllum occurs in Queensland. These ferns have a peculiar growth-habit in common. The plants have their main root-system in the ground, but climb to a considerable height up the trunks of trees, attaching themselves by roots which grow from the ventral surface of their climbing rhizomes. The fronds are always dimorphic, fertile fronds having contracted leaflets which are covered beneath with sporangia. The only other genus all species of which have a similar growth-habit is Stenochlaena (with which Lomariopsis and Teratophyllum were formerly united). Stenochlaena differs in the following characters: the rhizome is not dorsiventral in structure, and has a quite different and very complex vascular anatomy; the fertile leaflets have a distinct thin indusium-like edge; and the spores have a strongly sculptured exine lacking perispore. There is also one species of Blechnum in New Zealand which has a similar habit [B. filiforme (A. Cunn.) Ettings.]. This also has a rhizome which is not dorsiventral, but its vascular structure is much simpler than that of Stenochlaena, its fertile pinnae have more conspicuous indusium-like edges, and the spores have a smooth exine covered by perispore.