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. Stomata present; anomocytic.
The mesophyll with spherical etherial oil cells.
Stem anatomy. Nodes unilacunar (with two traces). Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with libriform fibres. Vessel end-walls horizontal; simple. Primary medullary rays wide (and high). Wood parenchyma diffuse to apotracheal. Sieve-tube plastids S-type.
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 unit 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, biochemistry. Saponins/sapogenins absent. Aluminium accumulation not found.
Geography, cytology. Neotropical. Juan Fernandez. X = 40, 42.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Magnoliiflorae; Magnoliales. Cronquist’s Subclass Magnoliidae; Magnoliales. APG 3 core angiosperms; Superorder Magnolianae; Order Piperales.
Species 1. Genera 1; only genus, Lactoris.