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The families of flowering plants

L. Watson and M.J. Dallwitz

Nyssaceae Dum.

~ Cornaceae p.p.

Habit and leaf form. Trees (mostly), or shrubs. Plants green and photosynthesizing. Leaves persistent; 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. The leaf lamina dorsiventral (with a single palisade layer). Mucilaginous epidermis present. Stomata present; mainly confined to one surface (abaxial); at least in Nyssa, paracytic. Hairs present; glandular, or eglandular and glandular (? - not of the unicellular and 2–armed type common in Cornaceae, the glandular hairs unicellular). The mesophyll with sclerenchymatous idioblasts (these traversing the width of the lamina); containing crystals. The crystals druses (only, in Nyssa), or druses and solitary-prismatic (Camptotheca). Main veins vertically transcurrent (via thin walled parenchyma).

Axial (stem, wood) anatomy. Pith with diaphragms. Secretory cavities absent. Cork cambium present; initially superficial (where observed, in Nyssa). Nodes tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The wood diffuse porous. The vessels small; solitary, radially paired, and in radial multiples (the latter short). The vessel end-walls oblique; scalariform. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with fibre tracheids; with libriform fibres, or without libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal. The secondary phloem not stratified. ‘Included’ phloem absent. The wood not storied.

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

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in racemes, or in heads, or in umbels. The ultimate inflorescence units 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 with distinct calyx and corolla (more or less), 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; 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, phytochemistry. Sugars transported as sucrose. 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).

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 III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Cornales (as a synonym of Cornaceae).

Species 10. Genera 2; Camptotheca, Nyssa.

General remarks. See Eyde (1988). Differing from Cornaceae in the racemose inflorescences, more numerous stamens and epitropous ovules, and with the compiled data offering assorted differences in leaf and stem anatomy as well.

Illustrations. • Nyssa multiflora and N. ogeche: Nat Pflanzenfam. III. • Nyssa sinensis: Hook. Ic. Pl. 20 (1891). • Leaf TS and epidermis of Nyssa caroliniana and Camptotheca acuminata, with foliar trichomes of Cornus (Cornaceae), Corokia (Argophyllaceae) and Marlea (= Alangium, Alangiaceae): Solereder, 1908.

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: 15th April 2018.’.