Philadelphaceae D. Don

~ Hydrangeaceae

Excluding Pterostemonaceae

Habit and leaf form. Small trees, or shrubs (or subshrubs). Leaves deciduous; opposite, or whorled; flat; petiolate; simple. Lamina entire; pinnately veined, or palmately veined. Leaves exstipulate. Lamina margins entire, or serrate, or dentate. Domatia recorded (Philadelphus); represented by hair tufts.

Leaf anatomy. Hairs present. Complex hairs present; usually stellate.

Lamina dorsiventral. Minor leaf veins without phloem transfer cells (Carpenteria, Philadelphus).

Stem anatomy. Secondary thickening developing from a conventional cambial ring. Wood parenchyma apotracheal (consisting of only a few scattered cells).

Reproductive type, pollination. Hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in `inflorescences' (usually), or solitary (occasionally); when aggregated, in cymes, or in racemes, or in heads. Inflorescences terminal; terminal racemes, cymes or heads. Flowers medium-sized; fragrant (often), or odourless; regular. Free hypanthium absent.

Perianth with distinct calyx and corolla; (9-)10-12; 2 whorled; isomerous, or anisomerous. Calyx 4, or 5; 1 whorled; gamosepalous; lobed; regular; persistent; imbricate, or valvate. Corolla 5-7; 1 whorled; polypetalous; imbricate, or contorted, 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).

Gynoecium (3-)5(-7), or 1 (rarely). Carpels reduced in number relative to the perianth to increased in number relative to the perianth. Gynoecium syncarpous; synovarious (usually, more or less), or synstylovarious; superior to inferior. Ovary (1-)5-7 locular; sessile. Gynoecium stylate. Styles (2-)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. Seeds endospermic; small; winged, or wingless. Embryo well differentiated (small). Cotyledons 2. Embryo achlorophyllous (2/7); straight.

Physiology, biochemistry. Not cyanogenic. Iridoids recorded (in 7 Deutzia species). Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid absent (4 species, 3 genera). Ursolic acid absent. C3 (?), or CAM. CAM recorded in Philadelphus - Troughton et al. 1974.

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. Takhtajan's Subclass Rosidae; Rosanae; Saxifragales. Species 135. Genera 7; Carpenteria, Deutzia, Fendlera, Fendlerella, Jamesia, Philadelphus, Whipplea.

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