Family Nyssaceae

Nyssaceae Dum.

~ Cornaceae p.p.

Habit and leaf form. Trees (mostly), or shrubs. Plants non-succulent. Leaves evergreen; alternate; petiolate; non-sheathing; not gland-dotted; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate. Lamina margins entire, or dentate. Domatia occurring in the family; manifested as pockets.

Leaf anatomy. Mucilaginous epidermis present. Stomata present; paracytic. Hairs present; eglandular and glandular (not unicellular 2–armed).

Lamina dorsiventral; without secretory cavities. The mesophyll with sclerencymatous idioblasts.

Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Cortical bundles absent. Medullary bundles absent. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with fibre tracheids; with vessels. Vessel end-walls oblique; scalariform. Vessels without vestured pits. Wood parenchyma apotracheal. Pith with diaphragms.

Reproductive type, pollination. Unisexual flowers present. Plants monoecious, or dioecious, or polygamomonoecious (?).

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in racemes, or in heads, or in umbels. The ultimate inflorescence unit racemose. Inflorescences pedunculate heads, short racemes or compact umbels, or sometimes reduced to a single flower. Flowers small; regular, or somewhat irregular; cyclic. Free hypanthium absent.

Perianth more or less with distinct calyx and corolla, or sepaline (the calyx sometimes virtually obsolete); 5, or 10(–15); isomerous, or anisomerous. Calyx minutely 5 (toothed, or reduced to an irregularly toothed rim); when pronounced, slightly gamosepalous; entire, or lobulate, or blunt-lobed, or toothed; unequal but not bilabiate, or regular; open in bud. Corolla (4–)5(–8); polypetalous (the petals small); more or less valvate (Camptotheca), or imbricate; regular.

Androecium in staminate and hermaphrodite flowers (8–)10(–16). Androecial members free of the perianth; free of one another; 2(–3) whorled. Androecium exclusively of fertile stamens, or including staminodes (some of the members sometimes imperfect in hermaphrodite flowers). Stamens (8–)10(–15); isomerous with the perianth to diplostemonous; alternisepalous (in male flowers), or oppositisepalous (in hermaphrodite flowers); filantherous (the filaments elongate-subulate, the anthers small). Anthers basifixed; not becoming inverted during development; dehiscing via longitudinal slits; latrorse, or introrse; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colporate; 2-celled.

Gynoecium (1–)2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 2 celled. Gynoecium syncarpous (but sometimes pseudomonomerous); synovarious to synstylovarious; inferior. Ovary 1 locular, or 2 locular (sometimes, in Nyssa). Epigynous disk present (large, pulviniform). Gynoecium stylate. Styles 1–2; partially joined; apical. Stigmas 1–2. Placentation when pseudomenomerous, parietal to apical; when bilocular, axile to apical. Ovules pendulous; epitropous; with ventral raphe; anatropous; unitegmic; tenuinucellate to crassinucellate. Endothelium differentiated. Endosperm formation cellular.

Fruit fleshy; indehiscent; a drupe, or a samara (obovate, compressed, drupaceous to subsamaroid). The drupes with one stone (1–2-loculed, these each opening apically by a triangular, apical-adaxial valve on germination). Fruit 1 seeded. Seeds fairly copiously endospermic. Endosperm oily (and also with hemicellulose). Embryo well differentiated (and rather large). Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Not cyanogenic. Alkaloids present (Camptotheca), or absent (3 species). Iridoids detected; ‘Route I’ type (+seco). Proanthocyanidins absent. Ellagic acid present. Aluminium accumulation not found (but accumulating cobalt). Sugars transported as sucrose.

Geography, cytology. Holarctic. Temperate to tropical. Southeast and Eastern Asia, Eastern U.S.A. X = 21, 22.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Cornales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Cornales (as a synonym of Cornaceae).

Species 10. Genera 2; Camptotheca, Nyssa.

See Eyde (1988).