from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of various ferns in the genus Ophioglossum, having leaves divided into a simple, sterile blade and a slender, spikelike spore-bearing segment. Also called adder's-tongue.
From the resemblance of the spike at the base of the frond to a snake's tongue.(American Heritage® Dictionary of the English Language, Fourth Edition)