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Ophioglossum L.

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