Family Psiloxylaceae

Psiloxylaceae Croizat

~ Myrtaceae

Habit and leaf form. Trees (with white bark); bearing essential oils. Leaves alternate; spiral; gland-dotted; aromatic (?); simple. Lamina entire; with an intramarginal nerve. Leaves exstipulate. Lamina margins entire.

Leaf anatomy. Lamina with secretory cavities. Secretory cavities containing oil; schizogenous.

Stem anatomy. Cork cambium present; initially deep-seated (from the pericycle). Internal phloem present. Secondary thickening developing from a conventional cambial ring. Xylem without fibre tracheids. Wood parenchyma apotracheal, or paratracheal.

Reproductive type, pollination. Unisexual flowers present. Plants dioecious, or polygamomonoecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in panicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences axillary; small axillary racemes or panicles. Flowers regular; 5 merous; cyclic; pentacyclic. Free hypanthium present.

Perianth with distinct calyx and corolla; 10, or 12; 2 whorled; isomerous. Calyx 5(–6); 1 whorled; polysepalous; regular; persistent; imbricate. Corolla 5(–6); 1 whorled; polypetalous; imbricate; regular; leathery; deciduous. Petals punctate, shortly clawed.

Androecium 10(–12). Androecial members free of the perianth (inserted on the perigynous disk); free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 10(–12); diplostemonous; oppositisepalous; inflexed in bud; filantherous (the filaments subulate). Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse (large, ovoid). Pollen grains aperturate; 3 aperturate; colporate (parasyncolporate).

Gynoecium 3–4 carpelled. Carpels reduced in number relative to the perianth. The pistil 3–4 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary 3–4 locular; stipitate. Gynoecium non-stylate. Styles from a depression at the top of the ovary; apical. Stigmas 1, or 3–4 (the ‘style lobes’ thick, fleshy, flattened, spreading and reflexed, persistent on the fruit); if viewed as single, 3–4 lobed. Placentation axile (with ovules over most of the somewhat peltate placenta, in many rows). Ovules 30–70 per locule (‘many’, no ovulodes); anatropous.

Fruit fleshy; indehiscent; a berry (small, punctate); many-seeded. Seeds non-endospermic. Embryo well differentiated (fleshy). Cotyledons flat. Embryo straight.

Geography, cytology. Paleotropical. Tropical. Mascarene Islands.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Myrtiflorae; Myrtales. Cronquist’s Subclass Rosidae; Myrtales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Myrtales (as a synonym of Myrtaceae?).

Species 1. Genera 1; only genus, Psiloxylon.