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The families of flowering plants

L. Watson and M.J. Dallwitz

Lactoridaceae Engl.

Habit and leaf form. Shrubs; bearing essential oils. Leaves small; alternate; distichous; petiolate; gland-dotted; simple. Lamina entire; obovate (emarginate); pinnately veined. Leaves stipulate. Stipules intrapetiolar (adnate to the petiole, large, sheathing); membranous; persistent. Lamina margins entire.

Leaf anatomy. Abaxial epidermis papillose. Stomata present; anomocytic. The mesophyll with spherical etherial oil cells.

Axial (stem, wood) anatomy. Nodes unilacunar (with two traces). Primary vascular tissues comprising a ring of bundles (separated by rays 2–3 cells wide); collateral. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays wide (and high).

The wood diffuse porous. The vessels small; solitary, radially paired, and in radial multiples. The vessel end-walls horizontal; simple. The vessels without spiral thickening. The axial xylem with fibre tracheids; with libriform fibres; without septate fibres. The parenchyma diffuse to apotracheal. ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Plants polygamodioecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences axillary; monochasia. Flowers small; 3 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline; 3; 1 whorled. Calyx 3; 1 whorled; polysepalous; imbricate.

Androecium 6. Androecial members free of the perianth; free of one another; 2 whorled. Androecium exclusively of fertile stamens, or including staminodes (in some flowers). Staminodes when present, 3; internal to the fertile stamens (the members of the inner androecial whorl); non-petaloid. Stamens 6; diplostemonous; alternisepalous (according to Hutchinson’s illustration); narrowly laminar (short). Anthers adnate; non-versatile; dehiscing via longitudinal slits; extrorse; bilocular (the sporangia well separated, nearly marginal, almost as long as the blade); tetrasporangiate; shortly appendaged (by a short prolongation of the connective). The anther appendages apical. Pollen shed in aggregates; in tetrads. Pollen grains aperturate; obscurely 1 aperturate; sulcate, or ulcerate (the aperture poorly defined).

Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 3 celled (basally). Gynoecium apocarpous to syncarpous; semicarpous (the carpels in a single whorl, medially more or less connate at the base); superior. Carpel shortly stylate; with a decurrent stigma; (4–)6(–8) ovuled. Placentation marginal (the placenta intruded). Ovary basally 3 locular. Ovules long funicled; biseriate; anatropous; bitegmic; weakly crassinucellate. Endosperm formation nuclear.

Fruit non-fleshy; an aggregate. The fruiting carpels coalescing into a secondary syncarp. The fruiting carpel dehiscent; a follicle. Seeds endospermic. Endosperm oily. Embryo well differentiated (very small). Cotyledons 2.

Physiology, phytochemistry. Saponins/sapogenins absent. Aluminium accumulation not found. Sieve-tube plastids S-type.

Geography, cytology. Neotropical. Juan Fernandez. X = 40, 42.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Magnoliiflorae; Magnoliales. Cronquist’s Subclass Magnoliidae; Magnoliales. APG III core angiosperms; Superorder Magnolianae. APG IV Order Piperales.

Species 1 (Lactoris fernandeziana). Genera 1; only genus, Lactoris.

Illustrations. • Lactoris fernandeziana: Bot. Jahrb. 8 (1877). • Lactoris fernandeziana: 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: 5th March 2018.’.