The families of flowering plants.
IncludingArbuteae (Arbutaceae) J.G Agardh, Arctostaphyleae (Arctostaphylaceae) J.G. Agardh, Cerantheraceae Dulac, Menziesiaceae Klotzsch, Rhododendra (Rhododendraceae) Juss., Rhodoraceae Ventenat, Siphonandraceae Klotzsch, Vacciniaceae S.F. GrayExcluding Empetraceae, Epacridaceae
Habit and leaf form. Small trees, or shrubs (often ‘ericoid’), or lianas (a few); bearing essential oils (rarely), or without essential oils. Self supporting, or epiphytic (sometimes), or climbing (a few). On acid substrates, helophytic to xerophytic. Leaves evergreen, or deciduous; minute to very large; alternate; spiral, or distichous, or four-ranked; ‘herbaceous’, or leathery; petiolate, or subsessile, or sessile; non-sheathing; gland-dotted, or not gland-dotted; aromatic (rarely), or without marked odour; simple; epulvinate. Lamina entire; acicular, or linear, or lanceolate to ovate; one-veined, or pinnately veined, or palmately veined; cross-venulate, or without cross-venules. Leaves exstipulate. Lamina margins flat, or revolute. Vegetative buds scaly, or not scaly. Leaves without a persistent basal meristem.
Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata anomocytic, or paracytic.
Lamina dorsiventral; with secretory cavities, or without secretory cavities. Secretory cavities when present, containing oil. Minor leaf veins without phloem transfer cells (5 genera).
Stem anatomy. Cork cambium present; initially deep-seated (usually), or superficial (e.g. Agapetes).Nodes unilacunar (usually), or tri-lacunar. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with tracheids, or without tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres; with vessels. Vessel end-walls scalariform, or scalariform and simple, or simple. Wood parenchyma apotracheal (or sparse, or absent). Pith homogeneous, or heterogeneous.
Reproductive type, pollination. Plants hermaphrodite (nearly always), or dioecious (Epigaea). Pollination (usually?) entomophilous; mechanism conspicuously specialized (occasionally - e.g. Kalmia, with explosively springing stamens), or unspecialized.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary; in racemes, in spikes, in heads, in corymbs, and in panicles. The ultimate inflorescence unit racemose. Inflorescences terminal, or axillary. Flowers bracteate; usually bracteolate (bracteoles usually 2 or 3); small to large; regular, or somewhat irregular to very irregular (Rhododendroideae). The floral irregularity (when apparent) involving the perianth and involving the androecium. Flowers (4–)5(–7) merous; cyclic; nearly always pentacyclic. Free hypanthium absent. Hypogynous disk usually present; intrastaminal.
Perianth with distinct calyx and corolla; (7–)10(–14); 2 whorled. Calyx (4–)5(–7); 1 whorled; polysepalous, or gamosepalous; cupuliform (usually), or cyathiform; fleshy (occasionally), or non-fleshy; persistent. Corolla (3–)5(–7); 1 whorled; gamopetalous (usually), or polypetalous (occasionally); imbricate, or valvate (less often); campanulate, or urceolate, or hypocrateriform, or funnel-shaped, or tubular; regular (usually), or bilabiate; white, or red, or pink, or purple; persistent, or deciduous.
Androecium 8–10 (usually), or 5 (Loiseleuria). Androecial members free of the perianth; all equal, or markedly unequal; free of one another; 1 whorled (occasionally), or 2 whorled (usually). Androecium exclusively of fertile stamens. Stamens 5 (rarely), or 8–10; isomerous with the perianth (rarely, when the antepetalous cycle is absent), or diplostemonous (usually); alternisepalous (usually obdiplostemonous), or alternisepalous (rarely, when the antepetalous cycle is wanting); alternating with the corolla members, or both alternating with and opposite the corolla members. Anthers dorsifixed, or basifixed; becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; versatile; dehiscing via pores to dehiscing via short slits (nearly always), or dehiscing via longitudinal slits (Epigaea, Loiseleuria, Leiophyllum); finally introrse, or latrorse; bilocular; tetrasporangiate; appendaged (commonly), or unappendaged (most Rhododendroideae). The anther appendages when present apical, or dorsal. Endothecium developing fibrous thickenings, or not developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall of the ‘dicot’ type, or of the ‘reduced’ type (Gaultheria). Pollen shed in aggregates (typically), or shed as single grains (e.g. Enkianthus); with viscin strands (especially Rhododendroideae), or without viscin strands; usually in tetrads. Pollen grains aperturate; 3 aperturate; colporate; not lophate; 2-celled (in 7 genera), or 3-celled (Enkianthus only).
Gynoecium (2–)4–5(–7) carpelled (7 in Bejaria). Carpels isomerous with the perianth, or reduced in number relative to the perianth. The pistil (1–)4–5(–7) celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior. Ovary (1–)4–5(–7) locular (usually with the locules opposite the corolla lobes). Gynoecium stylate. Styles 1; attenuate from the ovary, or from a depression at the top of the ovary; apical. Stigmas 1; usually capitate (greatly expanded in Epigaea). Placentation axile, or apical. Ovules 1–50 per locule (i.e. to ‘many’); pendulous to ascending; epitropous in Arctostaphylos; non-arillate; anatropous, or campylotropous, or hemianatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization, or fusing only after one has been fertilized, or fusing simultaneously with the male gamete (? — sometimes ‘only in association with a male gamete’ in Vaccinium). Antipodal cells formed; 3; proliferating (e.g. in Leucothoë), or not proliferating. Synergids pear-shaped, or hooked (often). Endosperm formation usually cellular. Endosperm haustoria present; chalazal and micropylar. Embryogeny solanad.
Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry, or a drupe, or a nut (rarely); occasionally enclosed in the fleshy perianth. Capsules septicidal, or loculicidal. The drupes with separable pyrenes, or with one stone (?). Dispersal unit the seed, or the fruit. Seeds copiously endospermic. Endosperm oily. Seeds minute, or small; winged (commonly), or wingless. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (4/8); straight.
Physiology, biochemistry. Cyanogenic (rarely), or not cyanogenic. Alkaloids present (rarely), or absent. Iridoids detected; ‘Route I’ type (?), or ‘Route II’ type (+decarb.). Verbascosides not detected. Proanthocyanidins nearly always present; cyanidin, or cyanidin and delphinidin. Flavonols present; kaempferol, or quercetin, or kaempferol and quercetin, or quercetin and myricetin, or kaempferol, quercetin, and myricetin (and sometimes with gossypetin). Ellagic acid present (only in the 3 species of Arbutus screened), or absent (14 species, 13 genera, including Arctostaphylos). Arbutin present (in many genera). Andromedotoxin recorded. Ursolic acid present. Saponins/sapogenins absent. Aluminium accumulation not found. Sugars transported as sucrose (Arbutus), or as oligosaccharides + sucrose (Rhododendron). Inulin recorded (possibly, in Calluna, Gibbs 1974). C3. C3 physiology recorded directly in Arctostaphylos, Rhodendrodendron. Anatomy non-C4 type (widely examined by L.W.).
Geography, cytology. Frigid zone and temperate, or sub-tropical to tropical (then usually at high altitude). Almost cosmopolitan, but tropical representation mostly at high altitude, and poorly represented in Australasia. X = (8–)12 or 13(–23).
Taxonomy.Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Ericales. Cronquist’s Subclass Dilleniidae; Ericales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 1350. Genera about 100; Acrostemon, Agapetes, Agarista, Andromeda,Anomalanthus, Anthopteropsis, Anthopterus, Arachnocalyx,Arbutus, Arctostaphylos, Bejaria, Bruckenthalia, Bryanthus,Calluna, Calopteryx, Cassiope, Cavendishia, Ceratostema,Chamaedaphne, Coccosperma, Coilostigma, Comarostaphylis,Costera, Craibiodendron, Daboecia, Demosthenesia, Didonica,Dimorphanthera, Diogenesia, Diplarche, Diplycosia, Disterigma,Eremia, Eremiella, Erica, Findlaya, Gaultheria,Gaylussacia, Gonocalyx, Grisebachia, Harrimanella, Kalmia,Kalmiopsis, Killipiella, Lateropora, Ledothamnus, Ledum,Leiophyllum, Leucothoë, Loiseleuria, Lyonia, Macleana,Macnabia, Malea, Menziesia, Mitrastylus, Mycerinus,Nagelocarpus, Notopora, Oreanthes, Ornithostaphylos,Orthaea, Oxydendrum, Pellegrinia, Pernettya, Pernettyopsis,Phyllodoce, Pieris, Platycalyx, Plutarchia, Polyclita,Psammisia, Rhododendron, Rhodothamnus, Rusbya, Salaxis,Satyria, Scyphogyne, Semiramisia, Simocheilus, Siphonandra,Sphyrospermum, Stokoeanthus, Sympieza, Syndsmanthus,Tepuia, Thamnus, Themistoclesia, Therorhodion, Thibaudia,Thoracosperma, Tsusiophyllum, Utleya, Vaccinium, Xylococcus,Zenobia.
General remarks. See Watson 1965; Watson, Williams and Lance 1967; Stevens 1971.
Economic uses, etc. Edible berries from Arctostaphylos, Gaylussacia, Vaccinium etc. (bearberry, bilberry, blueberry, whortleberry, buckleberry, cranberry etc). Many species and genera are cultivated as ornamentals (e.g. Erica, Rhododendron,Arbutus, Pieris). ‘Briar’ pipes are made from Erica spp.