Small, fleshy, terrestrial ferns, or moderate-size epiphytes. Rhizome short, fleshy, erect or creeping, siphonostelic or sometimes dictyostelic, lacking scales or hairs, bearing 1 - several fronds simultaneously, each with a pair of flexhy stipule-like outgrowths at the base. Fronds stipitate, vernation not circinnate, the sterile segment (tropophore) simple, sometimes once-or-twice-forked, +/- entire, erect or spreading in terrestrial species, drooping and pendulous in epiphytic species, venation reticulate, the areoles with or without included free veinlets; the fertile segement stipitate, inserted at or near the base of the tropophore, or on the stipe, or the adaxial surface of the tropophore, linearl, erect or pendulous, with 2 rows of sporangia, with or without a small sterile apical lobe. Sporangia large, thick-walled, imbedded within the sporangiophore, dehiscing by a transverse slit, annulus lacking, exindusiate. Spores trilets, smooth to finely reticulate or punctate.
Subgenus Ophioglossum: terrestrial, a +/- clear cut demarcation between the stipe and sterile segment; venation with a secondary reticulum, or free veins, within the primary reticulum; fertile spike with a sterile apex; spores roundish, reticulate or punctate.
Subgenus Ophioderma: terrestrial or epiphytic, no clear cut demarcation between the stipe and sterile segment, the bade gradually attenuate; fertile stalk mostly distinctly adnate to the sterile segment; venation of primary aeroles only; fertile spike with sporangia to the apex; spores +/- triangular, smooth.
Species in Papuasia
|1a.||Fertile spike with sterile apex; demarcation between stipe and sterile segment clear cut; the sterile segment not, or only at the very base adnate to the fertile stalk; venation mostly with at least a few secondary veinlets; terrestrial; (subg. Ophioglossum)...||2|
|Fertile spike with sporangia to the very tip; sterile segment gradually attenuate into the stipe, the stipe often hardly discernable; the sterile segment mostly adnate to the fertile stalk; venation of primary reticulum only; often epiphytes; (subgen. Ophioderma)...||7|
|2a.||Sterile segment linear or lanceolate, greater than 6-times as long as wide, apex nearly always acute; venation (especially in lower part of sterile segment) with mostly very long stretched areoles; marginal cells of the sterile segment very long-stretched, with the outer wall mostly slightly curved; (O. gramineum)...||3|
|Sterile segment never linear, less than 6 times as long as wide, apex often obtus, sometimes acute; venation never with very long-stretched areoles in the base of the sterile segment; marginal cells otherwise....||4|
|3a.||Plan 4-10cm high; stipe 1-6cm long; sterile segment 1.5-2cm long; fertile region 0.5-2cm long, often sharply set off against the stalk...||O. gramineum var. gramineum|
|Plant 9-25cm high; stipe 3.5-8cm long; sterile segment to 7.5cm long; fertile region to 7.5cm long, mostly gradually passing into the stalk...||O. gramineum var. majus|
|4a.||Marginal cells of sterile segment mostly +/- isodiametric with the outer wall quite straight, the margin quite smooth (sterile segment sometimes absent); mostly small plants 2-12(- 20) cm high...||O. nudicaule var. macrorhizum|
|Marginal cells of sterile segment rather variable in shape and often more wide than long, with the outer often clearly curved, the margin not so smooth; plants mostly higher; (O. reticulatum)...||5|
|5a.||Sterile segment in dried material rather coriaceous; venation rather dense...||O. reticulatum f. complicatum|
|Sterile segment in dried material thin; venation lax...||6|
|6a.||Sterile segment ovate-reinform or orbicular, the apex acute or obtuse, often apiculate, the base often clearly cordate; mostly rather many free-ending veinlets...||O. reticulatum f. reticulatum|
|Sterile segment ovate-lanceolate or trullate, the apex never obtus, often acuminate, never apiculate, the base at most slightly cordate; at most a few free-ending veinlets...||O. reticulatum f. dilatatum|
|7a.||Frond not or only slightly falcate up to 2(-4) m long, pendulous flaccid...||O. pendulum f. pendulum|
|Frond distinctly falcate, up to 60cm long, often not pendulous, more rigid...||8|
|8a.||Sterile segment clearly stalked, apec acute, never forked, venation in dried specimens mostly clearly visible...||O. pendulum f. nutans|
|Sterile segment gradually narrowed towards the base, apex obtus, often forked, venation, even in dried specimens, often hardly visible...||O. pendulum f. falcatum|