Plagiopteraceae Airy Shaw
~ Celastraceae, Flacourtiaceae
Habit and leaf form. Lianas (of combretaceous or malpighiaceous aspect, shortly ferrugineously stellate-pubescent); laticiferous. Climbing. Leaves opposite; membranous; simple. Lamina entire. Leaves exstipulate. Vernation conduplicate.
General anatomy. Plants with laticifers (the contents rubberlike). The laticifers in leaves and in stems.
Leaf anatomy. Hairs present. Complex hairs present; stellate (ferrugineous).
Stem anatomy. Vessels with vestured pits (the vestures ‘rudimentary', Jansen et al. (2000)).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in umbels and in panicles. The ultimate inflorescence unit cymose. Inflorescences many-flowered, sub-umbelliform aggregates of thyrsiform groups. Flowers small; very fragrant; regular. Free hypanthium absent.
Perianth with distinct calyx and corolla; 6, or 8, or 10; 2 whorled; isomerous. Calyx (3–)4(–5); 1 whorled; gamosepalous (small, shortly united below); regular; open in bud. Corolla (3–)4(–5); 1 whorled; polypetalous; valvate (externally pubescent); regular (and revolute).
Androecium 30–100 (‘many’). Androecial members maturing centrifugally; free of the perianth; free of one another; 2 whorled (‘biseriate’). Androecium exclusively of fertile stamens. Stamens 30–100 (‘many’); polystemonous; filantherous (the filaments filiform-subclavate). Anthers small, more or less horizontal; dehiscing transversely; four locular; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer; of the ‘dicot’ type. Tapetum glandular (the cells becoming 2–4 nucleate). Pollen grains 3-celled.
Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 3 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 3 locular; sessile. Gynoecium stylate. Styles 1 (elongate, subulate); apical. Stigmas 3 (‘style slightly three-lobed’). Placentation basal to axile. Ovules 2 per locule; ascending; collateral; anatropous; bitegmic (inner and outer integuments 3 and 4 cells thick, respectively); weakly crassinucellate (parietal tissue one-layered). Outer integument contributing to the micropyle. Endothelium differentiated (nucellar tissue disintegrating early). Embryo-sac development Polygonum-type. Antipodal cells formed; proliferating (to 15–20 cells); ephemeral. Synergids pear-shaped. Hypostase absent.
Fruit non-fleshy; dehiscent; a capsule (turbinate). Capsules finally septicidal (with three apical, spathulate wings). Micropyle zigzag.
Geography, cytology. Paleotropical. Tropical. Burma.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Malvales. Cronquist’s Subclass Dilleniidae; Violales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales (as a synonym of Celastraceae).
Species 1. Genera 1; only genus, Plagiopteron.
This description is rather inadequate, but see Ya Tang (1994) for embryology.