Adder's Tongue Family

Terrestrial ferns, deciduous perennials, often clone forming by root proliferation. Rhizome spherical, subspherical or elongated, erect or creeping, subterranean; roots fleshy without roothairs. Fronds 1 or few, consisting of a simple, hairless sterile, slightly fleshy lamina and a simple or compound, fertile, linear, stalked spike. Sporangia sunken in the tissue on either side of the linear spike, large, thick-walled, dehiscing by a slit into 2 valves, exindusiate, homosporous.