The families of flowering plants

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L. Watson and M. J. Dallwitz

Alangiaceae DC.

~ Cornaceae

Including Metteniusaceae Karst.

Habit and leaf form. Trees, or shrubs (sometimes spiny), or lianas (occasionally); laticiferous. Self supporting, or climbing (occasionally). Leaves alternate; spiral; petiolate; non-sheathing; gland-dotted, or not gland-dotted; simple. Lamina sometimes dissected (lobed), or entire; pinnately veined, or palmately veined; cross-venulate. Leaves exstipulate. Domatia occurring in the family (in several species); manifested as pits.

General anatomy. Plants with laticifers, or without laticifers (? — not mentioned by Metcalfe and Chalk). Plants without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral (usually, with a single palisade layer), or bifacial, or centric. Stomata present; mainly confined to one surface (abaxial); usually anomocytic. Hairs present, or absent (? sometimes with unequally 2–armed or stellate hairs); eglandular, or glandular. Adaxial hypodermis present, or absent. The mesophyll containing crystals. The crystals druses, or solitary-prismatic.

Axial (stem, wood) anatomy. Secretory cavities absent. Nodes tri-lacunar. Secondary thickening developing from a conventional cambial ring.

The wood semi-ring porous, or diffuse porous. The vessels medium. The vessel end-walls oblique; scalariform, or simple. The vessels without vestured pits; without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma diffuse apotracheal.

Reproductive type, pollination. Plants hermaphrodite, or dioecious (in Madagascar).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (with articulated pedicels); in cymes. The ultimate inflorescence units cymose. Inflorescences axillary; cymes. Flowers regular.

Perianth with distinct calyx and corolla; 8–20; 1 whorled, or 2 whorled; isomerous, or anisomerous. Calyx 4–10 (or obsolete); 1 whorled; gamosepalous; entire, or lobulate, or blunt-lobed, or toothed. Calyx lobes markedly shorter than the tube. Degree of gamosepaly (maximum length joined/total calyx length) 0.75–1. Calyx regular (the lobes lanceolate or truncate). Corolla 4–10, or 5; 1 whorled; polypetalous, or gamopetalous (the reflexing, linear petals sometimes basally coherent). Corolla lobes when gamopetalous, markedly longer than the tube. Corolla valvate.

Androecium 4–40. Androecial members free of the perianth, or adnate, or free of the perianth and adnate; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4–40; isomerous with the perianth, or diplostemonous to polystemonous. Filaments not appendiculate. Anthers dorsifixed (rarely), or basifixed; when dorsifixed versatile, or non-versatile; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. The initial microspore tetrads isobilateral. Anther wall initially with one middle layer. Tapetum glandular (?). Pollen grains aperturate; (2–)3–4(–8) aperturate; colpate, or porate, or colporate (colporoidate); 2-celled.

Gynoecium 2(–3) carpelled. The pistil 1 celled, or 2 celled. Gynoecium syncarpous (but often pseudomonomerous); eu-syncarpous; inferior. Ovary 1 locular, or 2 locular. Epigynous disk usually present (covering the top of the ovary), or absent. Styles 1. Stigmas 1; 1–3 lobed; truncate, or clavate. Placentation when unilocular apical; when bilocular apical. Ovules in the single cavity when unilocular, 1; 1 per locule; pendulous; with lateral raphe (and lateral micropyle), or with lateral raphe to with dorsal raphe; anatropous; unitegmic (Davis), or bitegmic (? - according to Hutchinson, who uses this feature in his key); crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed; proliferating (to 12 or more cells). Synergids pear-shaped. Hypostase present. Endosperm formation cellular, or nuclear.

Fruit fleshy; indehiscent; a drupe. The drupes with one stone (endocarp crustaceous or woody, one-seeded). Dispersal unit the fruit. Fruit 1 seeded. Seeds endospermic. Endosperm oily (and fleshy). Cotyledons 2 (foliaceous). Embryo chlorophyllous (1/1); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Alkaloids present, or absent. Iridoids detected; ‘Route I’ type (normal and seco). Saponins/sapogenins present. Proanthocyanidins absent. Ellagic acid absent. Aluminium accumulation not found.

Geography, cytology. Tropical. Alangium is represented in tropical Africa, Madagascar, China, SE Asia, Indo-malesia and SE Australia, while Metteniusa is restricted to NW tropical S. America. X = 11 (mainly), or 8 or 9.

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

Species about 20. Genera 2; Alangium (about 17 species), Metteniusa (3 species).

General remarks. Apart from ‘esoteric characters’ relying on small samples (wood anatomy, embryology, phytochemistry), Alangiaceae differ from Cornaceae sensu stricto (q.v) only in being laticiferous and in the apical placentation of the ovary. These families exemplify the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli, although the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993).

Illustrations. • Technical details: Alangium begonifolia. • Alangium platanifolia: as Marlea begonifolia, Bot. Reg. XXIV, 61 (1838). • Foliar trichomes of Marlea (= Alangium nobile), with Cornus (Cornaceae) and Corokia (Argophyllaceae), also leaf TS of Nyssa (Nyssaceae): Solereder, 1908.

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using 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).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 16th May 2016.’.