Their cosmopolitan distribution is mainly in tropical and subtropical habitats.Ophioglossum, the adder's-tongue ferns, is a genus of about 25-30 species of ferns in the family Ophioglossaceae, of the order Ophioglossales. The name Ophioglossum comes from the Greek, and means "snake-tongue".
Adders-tongues are so-called because the spore-bearing stalk is thought to resemble a snake's tongue. Each plant typically sends up a small, undivided leaf blade with netted venation, and the spore stalk forks from the leaf stalk, terminating in sporangia which are partially concealed within a structure with slitted sides.
When the leaf blade is present, there is not always a spore stalk present, and the plants do not always send up a leaf, sometimes going for a year to a period of years living only under the soil, nourished by association with soil fungi.
The plant grows from a central, budding, fleshy structure with fleshy, radiating roots.
Ophioglossum has a high chromosome count in comparison to other species, with 120 or up to 720 chromosomes possible in intervals of 120 due to polyploidy (multiple possible copies of chromosomes).
Species of Ophioglossum include: