The families of flowering plants

L. Watson and M.J. Dallwitz

Philadelphaceae D. Don

~ Hydrangeaceae.

Excluding Pterostemonaceae.

Habit and leaf form. Small trees, or shrubs (or subshrubs). Leaves deciduous; opposite, or whorled; flat; petiolate; not gland-dotted; simple. Lamina entire; pinnately veined, or palmately veined. Leaves exstipulate. Lamina margins entire, or serrate, or dentate. Domatia occurring in the family (Philadelphus); manifested as hair tufts.

Leaf anatomy. The leaf lamina dorsiventral. Hairs present; eglandular; unicellular, or unicellular and multicellular (?). Unicellular hairs simple. Complex hairs present, or absent; if present, usually stellate. Minor leaf veins without phloem transfer cells (Carpenteria, Philadelphus).

Axial (stem, wood) anatomy. 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.

The wood ring porous to diffuse porous. The vessels very numerous, small; solitary, or radially paired, or in radial multiples, or in tangential arcs. The vessel end-walls scalariform, or simple, or scalariform and simple. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids (?); without vasicentric tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres, or without libriform fibres; including septate fibres, or without septate fibres. The fibres with spiral thickening, or without spiral thickening. The parenchyma apotracheal (consisting of only a few scattered cells). The secondary phloem not stratified. ‘Included’ phloem absent. The wood not storied.

Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary (occasionally); when aggregated, in cymes (these few-flowered, in some Philadelphus spp.), or in racemes (ostensibly), or in heads, or in panicles. The ultimate inflorescence units seemingly essentially cymose. Inflorescences terminal. Flowers medium-sized; fragrant (often), or odourless; regular. Free hypanthium absent.

Perianth with distinct calyx and corolla; (8–)10–12; 2 whorled; isomerous, or anisomerous. Calyx 4, or 5–6; 1 whorled; gamosepalous; blunt-lobed; regular; persistent; imbricate, or valvate. Corolla 4 (commonly so, in Philadelphus), or 5–6; 1 whorled; polypetalous; imbricate, or contorted (e.g., in Philadelphus), or valvate; regular; usually white.

Androecium (4–)10–200 (to ‘many’, very numerous in Carpenteria). Androecial members branched (from a small number of primordia), or unbranched; when maturation sequence determinable, maturing centripetally; free of the perianth; free of one another, or coherent (sometimes basally connate). Androecium exclusively of fertile stamens. Stamens (4–)10–200 (i.e. to ‘many’); diplostemonous to polystemonous. Filaments appendiculate (sometimes lobed or toothed), or not appendiculate. Anthers dorsifixed to basifixed (mostly ‘almost basifixed’); versatile; dehiscing via longitudinal slits; almost latrorse (e.g. Whipplea), or introrse. Pollen grains aperturate; 3 aperturate; colporate (colporoidate); 2-celled (in Deutzia, Jamesia and Philadelphus).

Gynoecium (3–)4 carpelled, or 5(–7) carpelled, or 1 carpelled (rarely). Carpels reduced in number relative to the perianth to increased in number relative to the perianth. The pistil (1–)4 celled, or 5–7 celled. Gynoecium syncarpous; synovarious (usually, more or less), or synstylovarious; superior to inferior. Ovary (1–)4 locular, or 5–7 locular; sessile. Gynoecium stylate. Styles (2–)4 (commonly in Philadelphus), or 5–7; free, or partially joined; apical. Stigmas dry type; papillate; Group II type (B(i)). Placentation when unilocular, apical; when plurilocular, axile (usually), or parietal (rarely). Ovules in the single cavity 1–50 (?); (1–)25–50 per locule (usually ‘many’); pendulous to ascending; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped. Endosperm formation cellular, or nuclear. Endosperm haustoria present (Deutzia, Philadelphus); micropylar.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal, or valvular (e.g., in Philadelphus, Carpenteria). Seeds endospermic; small; winged, or wingless. Embryo well differentiated (small). Cotyledons 2. Embryo achlorophyllous (2/7); straight.

Physiology, phytochemistry. C3 (?), or CAM. CAM recorded directly in Philadelphus — Troughton et al. 1974. Sugars transported as oligosaccharides + sucrose (in Philadelphus). Not cyanogenic. Iridoids detected (in 7 Deutzia species); ‘Route I’ type (?). Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid absent (4 species, 3 genera). Ursolic acid absent.

Geography, cytology. Holarctic and Paleotropical. Temperate to sub-tropical. Southern Europe to Eastern Asia, North and Central America, Philippines.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Rosales. APG III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Cornales (as a synonym of Hydrangeaceae).

Species 135. Genera 7; Carpenteria, Deutzia, Fendlera, Fendlerella, Jamesia, Philadelphus, Whipplea.

General remarks. Thanks to Mike Hackston (June 2007) for correcting an error in an earlier version of this description. It differs obscurely from that of Hydrangeaceae (q.v.) only in tendencies among overlapping characters (e.g., ovary placentation), and perhaps in foliar hair forms (the latter relying on limited sampling).

Illustrations. • Deutzia crenata: Lindley. • Le Maout and Decaisne: Philadelphus coronarius. • Deutzia corymbosa: Bot. Reg. xxvi, 5 (1840). • Deutzia scabra: Bot. Reg. 1718, 1835. • Jamesia americana: Bot. Mag. 101 (1875). • Philadelphus coronarius: Bot. Mag. 391, 1797. • Philadelphus coronarius: Bot. Mag. 391, text. • Philadelphus gordonianus: Bot. Reg. 1839, 32. • Philadelphus hirsutus: Bot. Reg. XXIV, 14, 1838. • Philadelphus mexicanus: Bot. Reg. 38, 1842. • Philadelphus mexicanus: Bot. Mag. 124 (1898). • Philadelphus speciosus, = ?: Bot. Reg. 2003, 1837. • Leaf hairs of Deutzia and Philadelphus: 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: 5th March 2018.’.