An Australian Government Initiative [logo]
Information about Australia's flora - Ferns of Australia and PNG
ANBG logo
Home > Gardens | CANBR > ferns > taxa

Lygodium Sw.

Terrestrial ferns with a short- or long-creeping underground rhizome, the fronds scandent and high-climbing. Rhizome dichotomous, protestelic, the young parts densely covered with coarse, multiseptate hairs, the fronds borne in two rows from the upper surface, the roots from beneath. Frond with an indeterminate, slender, twining rachis formed by a series of very unequal dichotomies, the main and lateral axes with 2 narrow wings towards the adaxial surface, the wings continuous with those of a lateral branch; primary branches short, often hardly developed, with a terminal dormant bud and subtended by 2 secondary branches bearing the leaflets, the secondary branches pinnate, bipinnate or dichotomous with each branch bearing a deeply palmatifid leaflet; leaflets entire, serrate or lobed, with a prominent or indistinct costule with oblique lateral veins 1-3 times forked and free to the margin, or anastomosing, the areoles without included free veinlets, the fertile leaflets sometimes contracted, the sporangia borne on specialised contracted segments or sorophores. Sorophores narrow, spreading from the edge of the fertile leaflets at the ends of most veins, the margins serrate, the costule with short lateral veins each bearing a single sporangium protected by an apically opening indusium attached along the vein, paraphyses absent; sporangia ovoid with a short lateral stalk, annulus of a single row of thickened cells at the narrower enda, directed away from the margin of the sorophore, dehiscing longitudinally. Spores trilete, pale, variously sculptured.

Species in Papuasia

1a. Venation of sterile leaflets free... 2
Venation of sterile leaflets reticulate... 8
2a. Primary rachis branch 4-10 mm long below the pair of secondary branches; rhizome wide-creeping, the fronds distinctly spaced... 3
Primary rachis branches hardly elongate, the pair of secondary branches thus almost sessile on the main rachis; rhizome short, the fronds close together... 4
3a. Secondary branches simply pinnate; leaflets articulate at the base and ultimately deciduous... L. microphyllum
Secondary branches apply bipinnate; leaflets not articulate at the base... L. japonicum
4a. Secondary rachis branches regularly pinnate, normally with 3-5 pinnae on each side of the axis (young or depauperate fronds may have fewer leaflets); leaflets simple or lobed, never dichotomous, sometimes with a thickening at the apex of the stalk... 5
Secondary rachis branches simple or dichotomously branched one or more times (in some case by alternate unequal dichotomy sub pinnate with 1-3 lateral leaflets); leaflets simple, forked or palmately branched, never thickened at the apex of the stalk... 6
5a. Leaflets all about equal and all stalked (the terminal ones sometimes geminate), not auricled or branched at the base, or rarely with short spreading basal lobes; leaflet stalks thickened at their junction with the lamina... L. salicifolium
Lateral leaflets larger towards the base of the secondary branch, the smaller distal ones sessile, the basal ones stalked and usually auricled or with obliquely spreading lobes or with subsidiary leaflets below them; leaflets stalks not thickened at the apex... L. flexuosum
6a. Leaflets strongly cordate on outer side at base... 7
Leaflets not strongly cordate on outer side at base... L. circinnatum
7a. Fertile tertiary branches evenly deltoid in outline, with quaternary leaflets of increasing length towards the base; sterile leaflets strongly auriculate cordate at the base... L dimorphum
Fertile leaflets not deltoid in outline, 10-15 mm wide including the sorophores, sometimes with 1-2 long branches at the base; sterile leaflets +/- cordate at the base... L. trifurcatum
8a. Secondary rachis branches, at least the upper ones, elongate and pinnate... L. reticulatum
Secondary rachis branches bearing 3 leaflets, the lateral ones sometimes forked, all arising 1-3 mm from the dormant apex of the primary rachis branch... L. versteegii