Ophioglossum

Ophioglossum, the adder's-tongue ferns, is a genus of about 50 species of ferns in the family Ophioglossaceae. The name Ophioglossum comes from the Greek meaning "snake-tongue". Their cosmopolitan distribution is mainly in tropical and subtropical habitats.

The genus has the largest number of chromosomes in the known plant kingdom, but contrary to popular belief does not have the largest number of chromosomes out of all known organisms, falling short to the protist Sterkiella histriomuscorum.

Description
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 slit 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 malviae is known as the world's smallest terrestrial fern.

Taxonomy
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). It has almost 1260 number of chromosomes in the meiocyte (spore mother cell) which undergo meiosis, the reduction division to form the spore with only one set of chromosomes getting incorporated into each spore. The species Ophioglossum reticulatum has the highest number of chromosomes found in any multicellular organism.

Phylogeny
Phylogeny of Ophioglossum

Species
, World Ferns listed the following species:


 * Goswamia
 * Ophioglossum costatum
 * Ophioglossum eliminatum – status uncertain
 * Ophioglossum gomezianum
 * Ophioglossum gujaratensis
 * Ophioglossum hitkishorei
 * Ophioglossum indicum
 * Ophioglossum isanensis
 * Ophioglossum malviae
 * Ophioglossum nudicaule
 * Ophioglossum raphaelianum
 * Ophioglossum rubellum
 * Ophioglossum trilokinathii
 * Haukia
 * Ophioglossum crotalophoroides
 * Ophioglossum opacum
 * Ophioglossum tuberosum
 * Whittieria
 * Ophioglossum engelmannii
 * Ophioglossum s.s.
 * Ophioglossum ammophilum – sometimes included in O. gomezianum
 * Ophioglossum austroasiaticum – possibly a synonym of O. reticulatum
 * Ophioglossum azoricum
 * Ophioglossum californicum
 * Ophioglossum caroticaule
 * Ophioglossum convexum
 * Ophioglossum coriaceum
 * Ophioglossum fernandezianum – doubtful species
 * Ophioglossum × giovanninii
 * Ophioglossum gracile – may be included in O. gramineum
 * Ophioglossum gracillimum
 * Ophioglossum gramineum
 * Ophioglossum harrisii
 * Ophioglossum jaykrishnae – provisionally accepted name
 * Ophioglossum kawamurae
 * Ophioglossum lancifolium
 * Ophioglossum latifolium
 * Ophioglossum lineare – possibly a synonym of O. parvifolium
 * Ophioglossum louisii
 * Ophioglossum lusitanicum
 * Ophioglossum lusoafricanum
 * Ophioglossum melipillense
 * Ophioglossum namegatae – probably a synonym of O. petiolatum
 * Ophioglossum oblongum
 * Ophioglossum parvifolium
 * Ophioglossum parvum
 * Ophioglossum petiolatum
 * Ophioglossum × pierinii
 * Ophioglossum polyphyllum
 * Ophioglossum × pseudoazoricum
 * Ophioglossum pusillum
 * Ophioglossum reticulatum
 * Ophioglossum sandieae
 * Ophioglossum scariosum
 * Ophioglossum thermale
 * Ophioglossum thomasii
 * Ophioglossum vulgatum
 * Ophioglossum yongrenense

Species that may be placed in this genus include:
 * Ophioglossum bergianum 	= Rhizoglossum bergianum
 * Ophioglossum falcatum = Ophioderma falcatum
 * Ophioglossum intermedium = Ophioderma intermedium
 * Ophioglossum simplex = Ophioderma simplex