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The families of flowering plants

L. Watson and M.J. Dallwitz

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. The mesophyll with spherical etherial oil cells (?).

Axial (stem, wood) anatomy. Secretory cavities present (in the cortex); with oil (?). Cork cambium present; initially deep-seated (from the pericycle). Internal phloem present. Secondary thickening developing from a conventional cambial ring.

The axial xylem without fibre tracheids. The 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 units 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 ovoid, larger than is usual in Myrtaceae, dorsifixed; versatile; dehiscing via longitudinal slits; introrse. 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 (as distinct from Myrtaceae). Ovary 3–4 locular; stipitate. Gynoecium ambiguously non-stylate to stylate. Styles 1, or 3–4 (having 3–4 subsessile, thick, fleshy, flattened, obtuse, spreading and reflexed “style-lobes”); from a depression at the top of the ovary; apical. Stigmas 3–4 (persistent on the fruit); 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 III core angiosperms; core eudicot; Superorder Rosanae; malvid. APG IV Order Myrtales (as a synonym of Myrtaceae?).

Species 1 (Psiloxylon mauritianum). Genera 1; only genus, Psiloxylon.

General remarks. Psiloxylon seems different from Myrtaceae sensu stricto (q.v.) only in the superior ovary with 3–4 stigmas.

Illustrations. • Psiloxylon mauritianum (as Fropiera): J.D. Hooker, Proc. Linn. Soc. 5 (1861).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.