Contains 4 accepted taxa overall.

Characteristics
Ophioglossum L.
ADDER'S-TONGUE
Classification
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OPHIOGLOSSALES
Ophioglossum
Citation
OPHIOGLOSSUM Linnaeus, Sp. Pl. 1062. 1753.
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TYPE: Ophioglossum vulgatum Linnaeus Lectotypified by Smith, Hist. Filicum 367. 1875.
Species
Scientific Name Common Name Herbarium Specimens Status Photos
Ophioglossum crotalophoroides Bulbous Adder's-tongue
Ophioglossum nudicaule Slender Adder's-tongue
Ophioglossum petiolatum Long-stem Adder's-tongue
Ophioglossum pycnostichum Southern Adder's-tongue
Identification Key
1.  Epiphyte, lax or pendent; sterile leaf simple or palmately lobed
2
1.  Terrestrial, erect; sterile
3
2.  Sterile blade palmately lobed (young leaves sometimes unlobed) (Cheiroglossa)
2.  Sterile blade linear, sometimes forked (Ophioderma)
3.  Stems spheric, cormlike, fleshy, 3-12 mm wide; leaves arising from deep cavity in top of stem; sterile blades usually lying flat on ground, deltate to cordate
3.  Stems upright, 1-5(10) mm wide; leaves arising at top of stem; sterile blades erect to spreading, mostly ovate to lanceolate
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4.  Sterile blade veins forming only branching or nonbranching, free, included veinlets within larger areoles
4.  Sterile blade veins in larger leaves forming small areoles within larger areoles
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5.  Roots 0.5-1.5 mm wide; sterile blades often folded, ovate to ovate-lanceolate, to 10 cm long, to 4.5 cm wide; sporophore (including stalk) 1.3-2.5 times as long as sterile blade; dried blades uniformly green without pale central band
5.  Roots 0.2-0.8 mm wide; sterile blades plane, ovate to lanceolate, to 4.5 cm long, to 1.7 cm wide; sporophore (including stalk) 2-6 times length of sterile blade; dried blades commonly with pale central band
Genus Synonyms
Synonym Full Citation Basionym Type
No synonyms found.