OPHIOGLOSSACEAE

only family in the fern order Ophioglossales, a primitive group not closely related to other ferns. The family contains three genera and about 55 species. Its members are characterized by leaves (fronds) that are divided into two parts, a sterile green blade and a fertile spike with spore-producing structures (sporangia) embedded in its tissues. Most species produce only one such frond each season. The separate genera are distinguished mainly by the position and structure of the sporangia. The genus Ophioglossum (adder's-tongue ferns), with tropical and temperate species, has sporangia in two rows near the tip of a usually unbranched, narrow, fertile spike. The genus Botrychium, distributed throughout the world, includes the grape ferns, moonworts, and rattlesnake fern. Helminthostachys, with one species (H. zeylanica) in Sri Lanka (Ceylon) and regions extending from the Himalayas to Queensland, Australia, has sporangia in small groups on both sides of the fertile spike.