This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Twining vine-like ferns. Leaves elongate, the rachis wiry and flexuous; leafy parts consisting of the stalked palmately lobed or pinnate (or compound) secondary pinnae, borne in pairs upon short stalks arising alternately from the rachis. Sporanges borne on contracted divisions of the leaf, as short or elongate spikes, the lower surface bearing a double row of imbricate hood-like indusia fixed by their broad bases and concealing each 1 (rarely 2) sporanges. [Name Greek, in allusion to the flexible rachis.]
About 26 species, mostly of tropical distribution. Type species: Lygodiutn scandens (L.) Sw.
129. 1801. Lygodium palmatum Sw. Syn. Fil. 154. 1806.
Rootstock slender, creeping. Stipes slender, flexible and twining; leaves 1°-3° long, their short alternate branches 2-forked, each fork bearing a nearly orbicular 4-7-lobed pinnule more or less cordate at the base with a narrow sinus; surfaces naked; fertile pinnules contracted, several times forked, forming a terminal panicle; sporanges solitary, borne on alternate veins springing from the flexuous midvein of the segments, each covered by a scale-like indusium.