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The families of flowering plants.                                                                                                                                                                

Adoxaceae Trauty

                       

 

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ExcludingSambucaceae

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. Hydathodes present. Stomata mainly confined to one surface (abaxial); anomocytic.

Lamina dorsiventral. The mesophyll not containing mucilage cells; without calcium oxalate crystals.

Stem anatomy. Primary vascular tissue centrifugal. Cortical bundles absent. Medullary bundles absent. Secondary thickening absent. Xylem without tracheids.

Reproductive type, pollination. Unisexual flowersabsent. 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 unit 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, biochemistry. 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) imply 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. It remains to be seen whether their true affinities (Cornales or Apiales? — a bone of contention since the nineteenth century) have now been satisfactorily resolved.

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