Family Marcgraviaceae

Marcgraviaceae Choisy

Habit and leaf form. Shrubs and lianas (mostly), or shrubs, or trees (small, seldom); non-laticiferous and without coloured juice. Self supporting, or epiphytic, or climbing; when climbing, root climbers. Often heterophyllous (the leaves dimorphic, those on juvenile rooting vegetative shoots sessile and distichous, those on nonrooting shoots petiolate and spiral). Leaves alternate; spiral and distichous; leathery; petiolate, or petiolate and sessile; not gland-dotted; simple; not peltate. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Domatia occurring in the family (2 genera); manifested as pits.

Leaf anatomy. Extra-floral nectaries present (often), or absent. Stomata present; staurocytic.

Adaxial hypodermis present (aqueous). Lamina dorsiventral. The mesophyll with sclerencymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals raphides. Minor leaf veins without phloem transfer cells (Norantea).

Stem anatomy. Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissue in a cylinder, without separate bundles. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids (septate or not); with libriform fibres. Vessel end-walls scalariform, or simple. Primary medullary rays mixed wide and narrow. Wood parenchyma apotracheal, or paratracheal.

Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite (often some sterile flowers). Pollination often ornithophilous (and pollinated by humming-birds, but sometimes self-pollinated or even cleistogamous).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in spikes, or in umbels. The ultimate inflorescence unit racemose. Inflorescences terminal; racemes, spikes or umbels, often pendulous. Flowers bracteate (some of the bracts — usually those associated with sterile flowers — strongly modified into brightly coloured, pitcherlike, saccate, spurred or hooded nectariferous organs); calyptrate, or not calyptrate; regular; cyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent.

Perianth with distinct calyx and corolla; 8–10; 2 whorled; isomerous. Calyx 4, or 5; 1 whorled; polysepalous, or gamosepalous (then basally connate); regular; imbricate. Corolla 4, or 5; 1 whorled; polypetalous, or gamopetalous (sometimes basally connate, often (Marcgravia) connate distally); calyptrate (Marcgravia), or not calyptrate (when not distally connate).

Androecium 3–40. Androecial members branched, or unbranched (?); free of the perianth, or adnate (sometimes adnate to the base of the petals); free of one another, or coherent. Androecium exclusively of fertile stamens. Stamens 3–40; isomerous with the perianth to polystemonous. Anthers dehiscing via longitudinal slits; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall initially with more than one middle layer (3 or 4). Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate (or colporoidate); 2-celled.

Gynoecium 2–8 carpelled. Carpels reduced in number relative to the perianth to increased in number relative to the perianth. The pistil 1 celled (initially), or 2–8 celled (when mature). Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 1 locular (initially), or 2–8 locular (ultimately becoming plurilocular by intrusion and fusion of the placental partitions). Gynoecium very shortly stylate, or non-stylate. Styles if detectable, 1; apical. Stigmas 1 (this simple or merely lobed). Placentation finally axile. Ovules 30–50 per locule (‘many’); anatropous; bitegmic; tenuinucellate. Outer integument not contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed (then the three nuclei degenerating early); when formed, 3; not proliferating; ephemeral. Endosperm formation cellular (with a micropylar haustorium in Marcgravia). Endosperm haustoria present; micropylar.

Fruit thick, rather fleshy to non-fleshy; indehiscent, or dehiscent (then only partly so, near the base); a capsule to capsular-indehiscent; without fleshy investment. Capsules basally loculicidal. Fruit 50–100 seeded (‘many’). Seeds scantily endospermic, or non-endospermic. Embryo well differentiated. Cotyledons 2. Embryo slightly curved, or straight.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Iridoids not detected. Proanthocyanidins present. Ellagic acid absent. Inulin recorded (several records, Gibbs 1974).

Geography, cytology. Neotropical. Tropical. Tropical and Central America, West Indies.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Theiflorae; Theales. Cronquist’s Subclass Dilleniidae; Theales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.

Species 100. Genera 5; Marcgravia, Norantea, Souroubea, Ruyschia, Caracasia.

Illustrations.
• Technical details: Marcgravia.
• Technical details: Ruyschia (Lindley).