Dioncophyllaceae Airy Shaw
Including Triphyophyllaceae Emberger
Habit and leaf form. Soft-wooded lianas. Plants ‘carnivorous’ (at least Triphyophyllum being insectivorous), or autotrophic (the other genera?). Trapping mechanism of Triphyophyllum active, or passive (?). The traps on young stems and leaves, constituted by multicellular, stalked or sessile secretory glands, recalling those of Droseraceae and Ancistrocladaceae, which secrete sticky, acid mucilage. Climbing; climbing by pairs of hooks or tendrils representing the forked tips of the leaf midribs. Heterophyllous (Triphyophyllum, which in addition to the hook-tipped climbing leaves has ‘normal’ leaves without hooks, and others which are wholly reduced to the midrib, circinnate and beset with numerous stalked and sessile glands), or not heterophyllous. Leaves alternate; ‘herbaceous’, or leathery; simple. Lamina entire; pinnately veined (mostly), or parallel-veined (the midrib-leaves of Triphyophyllum). Leaves exstipulate. Lamina margins entire to crenate (to crenulate, often undulate). Vernation circinnate (the midrib-leaves of Triphyophyllum), or not circinnate.
Leaf anatomy. Stomata present; cyclocytic, or actinocytic.
Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring, or anomalous; when anomalous, via concentric cambia (Dioncophyllum). ‘Included’ phloem present, or absent. Xylem with tracheids; with fibre tracheids. Vessel end-walls simple. Wood parenchyma apotracheal and paratracheal.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence unit cymose. Inflorescences more or less supra- axillary; lax, more or less supra-axillary cymes. Flowers bracteate (the bracts large or small); medium-sized; regular; pentacyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; small, polysepalous, or gamosepalous (then shortly connate basally). Calyx lobes markedly longer than the tube. Calyx regular; persistent; valvate, or open in bud. Corolla 5; 1 whorled; polypetalous; contorted; white; fleshy, or not fleshy; deciduous (caducous).
Androecium 10(–30). Androecial members free of the perianth; all equal, or markedly unequal; slightly coherent, or free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 10(–30); isomerous with the perianth, or diplostemonous, or triplostemonous; in Triphyophyllum, alternisepalous; both alternating with and opposite the corolla members. Anthers basifixed (ovoid or oblong); dehiscing via longitudinal slits; introrse; appendaged. The anther appendages apical (by elongation of the connective). Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; colporate.
Gynoecium 2 carpelled, or 5 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth. The pistil 1 celled. Gynoecium syncarpous; synovarious, or synstylovarious; superior. Ovary 1 locular. Gynoecium stylate. Styles 2, or 5; free, or partially joined; apical. Stigmas 2, or 5; variously capitate, feathery or punctiform; dry type; non-papillate; Group II type (IIA). Placentation parietal. Ovules in the single cavity 30–100 (‘many’); long funicled; anatropous; bitegmic; crassinucellate.
Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal (opening well before maturity, the seeds borne peltately on very long, thickened, rigid funicles). Seeds copiously endospermic. Endosperm not oily. Seeds large (discoid); winged (the wing thin and broad or narrow and thicker, surrounding the seed). Seeds with starch. Embryo well differentiated (large, axile). Cotyledons 2.
Seedling. Germination cryptocotylar.
Geography, cytology. Paleotropical. Tropical. West Africa. 2n = 36.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Theiflorae (?); Theales (?). Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Caryophyllanae; Order Caryophyllales.
Species 3. Genera 3; Dioncophyllum, Triphyophyllum, Habropetalum.
Airy Shaw 1951; not seen: Schmid, R. (1964), Bot. Jahrb. (Engl.) 83, 1–54.