Some 25-30, including:
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". 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 Oxytricha trifallax.
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). It has almost 1260 number of chromosomes in the meiocyte (gamete mother cell) which undergo meiosis, the reduction division to form the gamete with only one set of chromosome getting incorporated into each gamete. 
Species of Ophioglossum include:
- Ophioglossum austroasiaticum
- Ophioglossum azoricum
- Ophioglossum californicum
- Ophioglossum costatum
- Ophioglossum crotalophoroides
- Ophioglossum engelmannii
- Ophioglossum lusitanicum
- Ophioglossum malviae
- Ophioglossum nudicaule
- Ophioglossum pedunculosum
- Ophioglossum petiolatum
- Ophioglossum polyphyllum
- Ophioglossum pusillum
- Ophioglossum pycnosticum
- Ophioglossum reticulatum
- Ophioglossum tenerum
- Ophioglossum thermale
- Ophioglossum vulgatum
- eFloras: Ophioglossum . accessed 2.14.2014.
- Lukhtanov, Vladimir (2015-07-10). "The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms". Comparative Cytogenetics. 9 (4): 683–690. doi:10.3897/compcytogen.v9i4.5760. PMC 4698580.
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