Family Mastixiaceae

Mastixiaceae Van Tiegh.

~ Cornaceae

Habit and leaf form. Trees; resinous. Leaves evergreen; (sub-) opposite (or decussate), or alternate to opposite; leathery; petiolate; not gland-dotted; simple. Lamina entire; cross-venulate; attenuate at the base, or cuneate at the base. Leaves exstipulate. Lamina margins entire. Domatia occurring in the family (3 species); manifested as pits (by contrast with Cornaceae).

Leaf anatomy. Hairs often unicellular, 2–armed.

The mesophyll with sclerencymatous idioblasts.

Stem anatomy. Secretory cavities present (in the cortex and pith). Primary vascular tissue in a cylinder, without separate bundles. Cortical bundles present. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls oblique; scalariform (with numerous fine bars). Wood parenchyma paratracheal.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal; terminal dichotomous thyrses. Flowers bracteate; (bi-) bracteolate (the pedicels articulated); regular; 4–5 merous; cyclic; tetracyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4, or 5(–7); gamosepalous; regular; persistent; open in bud. Corolla 4, or 5(–6); 1 whorled; polypetalous; usually more or less valvate (the petal tips inflexed); regular; fleshy. Petals bilobed, or fringed.

Androecium 4, or 5(–6), or 8. Androecial members free of the perianth; all equal; free of one another; 1 whorled, or 2 whorled (when 8). Androecium exclusively of fertile stamens. Stamens 4, or 5(–6), or 8; isomerous with the perianth, or diplostemonous; oppositisepalous; erect in bud; filantherous (the filaments subulate, flattened). Anthers dorsifixed; dehiscing via longitudinal slits; latrorse; appendaged. The anther appendages apical (by slight prolongation of the connective). Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium ostensibly 1 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium monomerous (ostensibly), or syncarpous (i.e. considered pseudomonomerous); ostensibly of one carpel, or eu-syncarpous (if treated as pseudomonomerous); inferior. Carpel stylate; apically stigmatic (the style short, conical, with a punctiform stigma); 1 ovuled. Placentation apical. Ovary if considered syncarpous, 1 locular. Epigynous disk present (fleshy, intrastaminal). Gynoecium stylate. Styles 1 (stout); apical. Stigmas 1 (punctiform deeply bifid or lobed); 2 lobed, or 4–5 lobed. Placentation apical. Ovules in the single cavity 1; pendulous; epitropous; with ventral raphe; anatropous; unitegmic; crassinucellate.

Fruit fleshy. The fruiting carpel indehiscent; drupaceous (ovoid, with the endocarp grooved). Fruit treated as a syncarp, indehiscent; a drupe (with purple or blue pericarp). The drupes with one stone (the endocarp grooved). Fruit 1 seeded. Seeds copiously endospermic (the endosperm fleshy). Cotyledons 2 (foliaceous). Embryo small.

Physiology, biochemistry. Iridoids detected; ‘Route I’ type. Aluminium accumulation demonstrated.

Geography, cytology. Paleotropical. Tropical. Indomalayan.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Cornales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Cornales (as a synonym of Cornaceae).

Species 25. Genera 1; only genus, Mastixia.

Matthew 1976. Mastixia exemplifies the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli. This is interesting, given that the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993).