Description
Epiphytic, epilithic, or rarely terrestrial. Rhizomes dorsiventral, scaly with extra-axillary buds near the leaves. Rhizome creeping, usually long (short in Gymnogrammitis ), and densely covered with scales (and often also hairs in Leucostegia ). Leaves alternately in two ranks on the dorsal side of the rhizome and articulated at the base to phyllopodia. Extra-axillary buds alternately in two ranks on the ventral-lateral sides of the rhizome; each bud intermediate between two succeeding phyllopodia in Leucostegia and in Gymnogrammitis , lateral to the phyllopodium or lower lateral and slightly anterior in the other genera. Roots on the ventral side of lateral buds, in Leucostegia scattered on all sides of the rhizome, in Gymnogrammitis along the entire ventral side of it.
The vascular structure of the rhizome a dorsiventral dictyostele. Stele with a thick dorsal and a thick ventral vascular strand, in Gymnogrammitis only a thick dorsal strand. In Leucostegia the dorsiventral dictyostele has elongate leaf gaps with two simple leaf traces. In all other taxa many leaf traces for a leaf arise from the dorsal and ventral strands and from a strand connecting the two, and are finely anastomosing in each leaf gap. The connecting strands thin and obscure.
In Leucostegia scales basifixed with broad bases attached to the rhizome, often with hairs on the rhizome or on the base of the scales.
In the other genera the rhizome scales peltate or basally attached with a cordate, overlapping, base (sometimes called pseudo-peltate).
The scales acicular, flat and nearly acicular, evenly narrowed towards the apex above the much broader base, or just evenly narrowed. In a number of species apical and marginal multicellular hairs on the scales. Scales often ciliate or toothed, the ciliae or teeth consisting of two upturned ends of adjacent marginal cells.
Incision of the leaves very diverse, from an entire leaf to a decompound leaf with uni-veined ultimate segments, in Davallia repens even in an individual plant. Pinnules in Davalliaceae anadromous, the apical pinnule of at least the lower pinnae inserted nearer to the rachis than the basal pinnule, or catadromous, the other way round, in Davallodes and sometimes in Davallia membranulosa . Lamina often firm in texture, usually triangular, less often narrowed to the base. Axes adaxially grooved, the grooves with raised centre; edges of laminar parts continuous with the ridges (wings) bordering the axis groove; costae and costules adaxially convex. Lamina often firm in texture, usually triangular, sometimes narrowed towards the base; when mature mostly without macroscopical epidermal appendages (hairy in Davallodes and some species of Davallia ). Veins pinnately branched, free, ending behind the margin or reaching it. "False veins" occasionally present between the true veins.
Sori strictly terminal in Leucostegia , various in the other genera (facing midveins either at the bending point or at the forking point of veins); indusium attached at the base, often also at the sides or part of them, rarely reniform with a short point of attachment, or absent (in Gymnogrammitis ); soral trichomes present or not. Receptacle not elevated.
Chromosomes
In Leucostegia x = 41, the chromosome counts indicate that Leucostegia immersa in India and Taiwan is diploid (Tryon and Lugardon, 1991: 374); in Gymnogrammitis x = 36, the count from a plant in Yunnan, Dali also indicates diploidy (Kato et al., 1992: 108); in the other genera x = 40, triploidy and apogamy is reported in Davallia repens from Sri Lanka (Manton and Sledge, 1954).
Distribution
From Korea in the north to New South Wales and Three Kings Island north of New Zealand in the south, from west tropical Africa in the west to the Marquesas in the Pacific.