Family Sarcolaenaceae

Sarcolaenaceae Caruel

Alternatively Chlaenaceae Thou.

Including Rhodolaenaceae Bullock, Schizochlaenaceae Wetttst.

Habit and leaf form. Beautiful trees, or shrubs. Leaves mostly evergreen; alternate; leathery, or ‘herbaceous’ (?); petiolate (the petioles with complex anatomy, often siphonostelic with medullary bundles); non-sheathing; simple. Lamina entire; pinnately veined; cross-venulate. Leaves stipulate. Stipules often large, intrapetiolar (similar to those in Ficus); free of one another; usually caducous. Lamina margins entire.

Leaf anatomy. Stomata present; more or less anomocytic. Hairs present; eglandular and glandular; unicellular, or multicellular. Unicellular hairs branched, or unbranched. Multicellular hairs branched, or unbranched. Complex hairs present (often), or absent; peltate, or stellate (commonly).

Adaxial hypodermis present, or absent. Lamina dorsiventral. The mesophyll containing mucilage cells; containing calcium oxalate crystals. The mesophyll crystals druses.

Stem anatomy. Nodes tri-lacunar. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. The secondary phloem stratified into hard (fibrous) and soft (parenchymatous) zones. ‘Included’ phloem absent. Xylem with tracheids; with vessels. Vessel end-walls simple. Vessels with vestured pits. Primary medullary rays narrow (exclusively uniseriate). Wood parenchyma apotracheal (diffuse).

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in umbels, or in panicles. The ultimate inflorescence unit cymose. Inflorescences consisting of flowers borne singly or paired within involucres of various forms, in cymose aggregations; with involucral bracts (i.e. the solitary or paired flowers subtended by involucels of bractlets, these distinct or more or less connate, sometimes cupulate and then sometimes interpreted as derived from the pedicel tips). The involucres accrescent (often becoming lignified, surrounding the fruit), or non-accrescent. Flowers regular. Free hypanthium absent. Hypogynous disk present, or absent; extrastaminal; of separate members to annular (more or less cupular, entire or toothed, supposedly staminodial in origin).

Perianth with distinct calyx and corolla; 8(–11); isomerous to anisomerous. Calyx 3(–5); polysepalous (when 5, the two outer members smaller than the three inner, when four either one or three outer members smaller); imbricate. Corolla 5(–6); 1 whorled; polypetalous, or gamopetalous (the petals sometimes very slightly united at the base). Corolla lobes markedly longer than the tube. Corolla contorted.

Androecium 5–10 (Leptolaena), or 12–200 (? — usually very numerous). Androecial members branched; usually maturing centrifugally (?); free of the perianth; free of one another, or coherent (sometimes fasciculate, the bundles of filaments weakly connate at the base); when in bundles, 5–10 adelphous. Androecium exclusively of fertile stamens, or including staminodes (the disk sometimes thus interpretable). Staminodes when present, 5–10 (?). Stamens 5–10 (Leptolaena), or 30–200 (? — usually very numerous); polystemonous (usually), or isomerous with the perianth to diplostemonous (Leptolaena); filantherous (the filaments slender). Anthers dorsifixed, or basifixed; dehiscing via longitudinal slits; extrorse, or introrse; bilocular; tetrasporangiate. Pollen shed in aggregates; in tetrads. Pollen grains aperturate; 3–6 aperturate; colporate (parasyncolpate).

Gynoecium (1–)3–4(–5) carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth, or increased in number relative to the perianth. The pistil 1–5 celled. Gynoecium monomerous (rarely), or syncarpous (usually); of one carpel (rarely), or synstylovarious to eu-syncarpous; superior. Carpel (when monomerous) stylate; apically stigmatic; 1–3 ovuled (?). Ovary when syncarpous (i.e.usually), (1–)3–4(–5) locular. Gynoecium stylate. Styles 1; attenuate from the ovary; apical (usually thick, more or less elongated). Stigmas 1; expanded, usually lobed. Placentation basal to axile, or axile, or axile to apical. Ovules (1–)2–15 per locule (few to several); pendulous to ascending; anatropous.

Fruit non-fleshy. The fruiting carpel when monomerous, indehiscent; an achene, or nucular (?). Fruit dehiscent, or indehiscent; a capsule, or a nut. Capsules when dehiscent, loculicidal. Seeds endospermic (usually, copiously), or non-endospermic (endosperm seldom scanty or wanting). Endosperm not oily (fleshy or horny, starchy). Seeds with starch. Embryo well differentiated. Cotyledons 2 (cordate). Embryo straight.

Physiology, biochemistry. Aluminium accumulation not found.

Geography, cytology. Paleotropical. Tropical. Madagascar.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Malvales. Cronquist’s Subclass Dilleniidae; Theales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Malvales.

Species 40. Genera 10; Eremolaena, Leptolaena, Mediusella, Pentachlaena, Perrierodendron, Rhodolaena, Sarcolaena, Schizolaena, Xerochlamys, Xyloölaena.

Illustrations.
• Technical details: Leptolaena (Thonner).
• Technical details: Leptolaena (Lindley).