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The families of flowering plants

L. Watson and M. J. Dallwitz

Adoxaceae Trautv.

Excluding Sambucaceae.

Habit and leaf form. Small herbs (with long-petioled radical leaves and a pair of cauline leaves). 0.06–0.15 m high; rhizomatous (monopodial). Mesophytic. Leaves opposite (on the erect flowering stems, which bear a single pair); compound; epulvinate; ternate (and the radical leaves with ternately divided lobes); exstipulate.

Leaf anatomy. The leaf lamina dorsiventral. Hydathodes present (in groups on the upper surfaces of the leaf segments). Stomata mainly confined to one surface (abaxial); anomocytic. Hairs present; eglandular and glandular (including deciduous, tanniniferous secretory hairs on young leaves). The mesophyll not containing mucilage cells; without crystals.

Axial (stem, wood) anatomy. Primary vascular tissues of the flowering axis comprising 2 or 3–5 bundles, in the rhizome comprising consisting of dorsal and ventral, flattened strands; collateral. Cortical bundles absent. Medullary bundles absent. Secondary thickening absent.

The vessel end-walls scalariform. The axial xylem without tracheids.

Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Pollination entomophilous; ‘via small flies’.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (in a solitary, terminal head); in heads. The ultimate inflorescence units cymose. Inflorescences condensed dichasial cymes; more or less pseudanthial. Flowers small; somewhat irregular, or very irregular. The floral irregularity involving the perianth (this being anisomerous). Flowers 4 merous (the terminal one), or 5 merous (the laterals); tetracyclic. Free hypanthium present to absent (at most, slight).

Perianth with distinct calyx and corolla; 6 (in the terminal flower), or 8 (in the laterals); 2 whorled; anisomerous (resulting from the presence, usually, of only 2 or 3 calyx lobes). Calyx 2 (in the terminal flower), or 3 (in the laterals); 1 whorled; gamosepalous; persistent (basally adnate to the gynoecium). Corolla 4 (in the terminal flower), or 5 (in the laterals); 1 whorled; gamopetalous. Corolla lobes markedly longer than the tube. Degree of gamopetaly less than 0.2 (i.e., with a very short tube). Corolla green; deciduous.

Androecium 4 (in the terminal flower), or 5 (in the laterals). Androecial members branched (each stamen divided almost to the base); free of the perianth; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5 (but ostensibly 8 or 10); isomerous with the perianth; oppositisepalous; alternating with the corolla members (but superficially both alternating and opposite). Anthers basifixed; non-versatile; bilocular (providing they are recognised as such, the half anthers being unilocular); bisporangiate (but each ‘anther’ represents a half anther, the single stamen primordium having split). Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer. Tapetum amoeboid. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colpate to porate (colporoidate); 3-celled.

Gynoecium 3–5 carpelled. The pistil 3–5 celled. Gynoecium syncarpous; synovarious; partly inferior. Ovary 3–5 locular. Gynoecium stylate. Styles 3–5; free to partially joined; attenuate from the ovary; shorter than the ovary (very short). Stigmas 3–5; dry type; papillate; Group II type. Placentation axile to apical. Ovules 1 per locule; pendulous; anatropous; unitegmic; tenuinucellate. Embryo-sac development Adoxa-type. Polar nuclei fusing only after one has been fertilized, or fusing simultaneously with the male gamete (?). Antipodal cells formed; 2, or 3; not proliferating. Synergids pear-shaped. Endosperm formation cellular. Embryogeny asterad.

Fruit fleshy; indehiscent. Gynoecia of adjoining flowers combining to form a multiple fruit. Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo small.

Physiology, phytochemistry. Not cyanogenic. Iridoids detected; ‘Route I’ type (normal and seco). Proanthocyanidins absent. Flavonols absent. Ellagic acid absent.

Geography, cytology. Temperate. North temperate. X = 9.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Araliiflorae, or Corniflorae; near Araliales (?); Cornales (?). Cronquist’s Subclass Asteridae; Dipsacales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; campanulid; Order Dipsacales.

Species 3. Genera 3; Adoxa, Sinadoxa, Tetradoxa.

General remarks. This description was encoded with reference only to A. moschatellina. rbcL sequence analyses by Backlund and Bremer (1997) implied close relationship between Adoxa, Sambucus and Viburnum; strongly supporting the taxonomic integrity of Bentham and Hooker’s tribe Caprifoliaceae-Sambuceae (= Adoxaceae sensu lato, e.g. Judd et al. 1984) but suggesting that these genera are relatively distant from Caprifoliaceae. Their true affinities have been a bone of contention since the nineteenth century, but may now have been resolved by referring them to Dipsacales; i.e., closer to Apiales than to Cornales.

Illustrations. • Technical details (Adoxa). • Adoxa moschatellina (B. Ent., 1825).

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: 19th October 2016.’.