The families of flowering plants

L. Watson and M.J. Dallwitz

Helwingiaceae Decaisne

~ Cornaceae.

Habit and leaf form. Glabrous shrubs. Plants green and photosynthesizing. Leaves alternate (to subopposite); spiral; very thinly ‘herbaceous’; petiolate; not gland-dotted; simple. Lamina entire; ovate lanceolate, or ovate; pinnately veined; cross-venulate. Leaves stipulate (the stipules often branched). Stipules intrapetiolar (on the petiole); free of one another; caducous. Lamina margins serrate (serrulate).

General anatomy. Plants without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral (but the palisade scarcely differentiated). Stomata present; mainly confined to one surface (abaxial); anomocytic. Hairs absent (leaves glabrous). Lamina without secretory cavities. The mesophyll without crystals. Main veins embedded. Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Secretory cavities absent. Nodes unilacunar. 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 vessel end-walls scalariform. The axial xylem without fibre tracheids; with libriform fibres; including septate fibres (a few), or without septate fibres. The parenchyma apotracheal. ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Plants dioecious.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in umbels. Inflorescences epiphyllous (from the upper side of the midrib); small epiphyllous umbels, the male flowers sometimes long pedicellate, the females shortly so. Flowers small; regular; 3–4(–5) merous; cyclic. Free hypanthium absent.

Perianth petaline (as described by Airy Shaw); 3–4(–5); 1 whorled. Corolla 3–4(–5); 1 whorled; polypetalous; valvate.

Androecium 3–4(–5). Androecial members free of the perianth; free of one another; 1 whorled. Androecium of male flowers, exclusively of fertile stamens. Stamens 3–4(–5); isomerous with the perianth; (theoretically) oppositisepalous; alternating with the corolla members; filantherous (inserted outside the flat angled disk). Anthers dehiscing via longitudinal slits; introrse. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 3–4 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 3–4 celled. Gynoecium syncarpous; synstylovarious; inferior. Ovary 3–4 locular. Epigynous disk present (passing into the style). Gynoecium stylate. Styles 1; apical; shorter than the ovary. Stigmas 3–4 (recurved). Placentation apical. Ovules 1 per locule; pendulous; apotropous; with dorsal raphe; anatropous.

Fruit fleshy; indehiscent; a drupe. The drupes with separable pyrenes (3–4). Fruit 3–4 seeded. Seeds endospermic. Embryo well differentiated (small). Embryo straight.

Physiology, phytochemistry. Iridoids not detected.

Geography, cytology. Holarctic. Temperate. Eastern Himalayas to Japan and Formosa. X = 19.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli (?). Dahlgren’s Superorder Araliiflorae; Araliales. Cronquist’s Subclass Rosidae; Cornales. APG III core angiosperms; core eudicot; Superorder Asteranae; campanulid. APG IV Order Aquifoliales.

Species 5. Genera 1; only genus, Helwingia.

Illustrations. • Helwingia cf. japonica (as rusciflora): Nat. Pflanzenfam. III (1898). • Helwingia ruscifolia: Lindley. • Helwingia ruscciflora: Le Maout and Decaisne.

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: 5th March 2018.’.