| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Tetrameristaceae (H. Hallier) Hutch.

Excluding Pellicieraceae.

Habit and leaf form. Trees, or shrubs. Plants green and photosynthesizing. Leaves alternate; leathery; subsessile, or sessile; non-sheathing; without marked odour; simple. Lamina entire; conspicuously asymmetric to not conspicuously asymmetric; pinnately veined; cross-venulate; slightly decurrent. Leaves exstipulate. Lamina margins entire.

General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral. Extra-floral nectaries present. Stomata present; anomocytic and paracytic. Adaxial hypodermis present. The mesophyll with sclerenchymatous idioblasts; containing crystals. The crystals raphides (and commonly also with crystal sand).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated. Nodes tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide.

The wood diffuse porous. The vessels large; solitary, radially paired, and in radial multiples. The vessel end-walls moderately oblique; scalariform, or scalariform and simple. The vessels without vestured pits; without spiral thickening. The axial xylem with libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal; wood not storied.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in umbels, or in corymbs. The ultimate inflorescence units racemose. Inflorescences axillary; umbelliform or compactly corymbiform racemes. Flowers bracteate; bi- bracteolate (the bracteoles persistent or deciduous); small; regular; 4 merous, or 5 merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium absent.

Perianth with distinct calyx and corolla; 8, or 10; 3 whorled (Tetramerista), or 2 whorled; isomerous. Calyx 4 (in two series, in Tetramerista), or 5; 2 whorled (Tetramerista), or 1 whorled; polysepalous (the members with numerous glandular pits adaxially); regular; persistent, or not persistent; imbricate. Corolla 4, or 5; 1 whorled; polypetalous; imbricate (scarcely longer than the sepals); regular; persistent, or deciduous (?).

Androecium 4, or 5. Androecial members free of the perianth; free of one another to coherent (the subulate filaments flattened, perhaps shortly coherent at the base); if coherent, 1 adelphous; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members; inflexed in bud (the anthers ultimately inverting to become extrorse). Anthers dorsifixed; dehiscing via longitudinal slits; extrorse. Pollen grains aperturate; 3 aperturate; (constricti-) colporate.

Gynoecium 4 carpelled, or 5 carpelled. Carpels isomerous with the perianth. The pistil 4 celled, or 5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 4 locular, or 5 locular. Gynoecium stylate. Styles 1; apical. Stigmas 1 (punctate or minutely lobed). Placentation basal to axile. Ovules 1 per locule; ascending; epitropous; anatropous; bitegmic.

Fruit fleshy; indehiscent; a berry; 4 seeded, or 5 seeded. Seeds copiously endospermic. Embryo well differentiated. Cotyledons 2. Embryo straight (basal).

Geography, cytology. Paleotropical and Neotropical. Tropical. Western Malaysia (Tetramerista and southern Venezuela (Pentamerista).

Taxonomy. Subclass Dicotyledonae; Crassinucelli, or Tenuinucelli (?). Dahlgren’s Superorder Theiflorae (?); Theales (?). Cronquist’s Subclass Dilleniidae; Theales. APG III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Ericales.

Species 4. Genera 2; Pentamerista, Tetramerista.

General remarks. See Hutchinson 1959, Maguire 1972.

Illustrations. • Tetramerista glabra: Ic. Bogorienses 4 (1901). • Tetramerista glabra: Hutchinson.

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: 8th June 2026. delta-intkey.com’.

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