The families of flowering plants
Habit and leaf form. Small trees, or shrubs. Plants autotrophic. Leaves evergreen, or deciduous; alternate; herbaceous, or leathery; petiolate to sessile; simple. Lamina entire; pinnately veined; cross-venulate. Leaves exstipulate (but with red, ligulate, glandular structures in the leaf axils). Lamina margins entire.
Leaf anatomy. The leaf lamina dorsiventral. Mucilaginous epidermis present, or absent. Stomata present; mainly confined to one surface (abaxial); anomocytic. The mesophyll containing crystals. The crystals druses, or druses and solitary-prismatic.
Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring.
The wood occasionally tending to semi-ring porous, or diffuse porous (usually). The vessels very small (and very numerous); solitary (usually, mostly), or clustered and in tangential arcs (sometimes, in late wood). The vessel end-walls oblique; scalariform. The vessels without vestured pits; without spiral thickening. The axial xylem with tracheids, or without tracheids; without vasicentric tracheids; with fibre tracheids; without libriform fibres; without septate fibres. The fibres without spiral thickening. The parenchyma apotracheal, or apotracheal and paratracheal. The secondary phloem not stratified. Included phloem absent. The wood not storied.
Root anatomy. Root xylem with vessels.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the perianth (from the petals, in Cyrilla), or from the disk, or from the perianth and from the disk (?).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in racemes. The ultimate inflorescence units racemose. Inflorescences terminal, or axillary. Flowers bracteate (the bract sometimes caducous); bracteolate; fragrant; regular; 5(–7) merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal.
Perianth with distinct calyx and corolla; 10(–14); 2 whorled; isomerous. Calyx 5(–7); 1 whorled; polysepalous, or gamosepalous (connate basally). Calyx lobes about the same length as the tube, or markedly longer than the tube (?). Calyx regular; persistent; accrescent (often), or non-accrescent; imbricate. Corolla 5(–7); 1 whorled; polypetalous, or gamopetalous (then shortly so at the base). Corolla lobes markedly longer than the tube. Corolla imbricate, or contorted; white, or red, or pink, or purple.
Androecium 5 (Cyrilla), or 10. Androecial members free of the perianth; all equal, or markedly unequal (those of the outer whorl longer, in Cliftonia); free of one another; 1 whorled (Cyrilla), or 2 whorled (5+5). Androecium exclusively of fertile stamens. Stamens 5 (representing the outer whorl, in Cyrilla), or 10; isomerous with the perianth (Cyrilla), or diplostemonous; oppositisepalous (alternating with the petals); erect in bud (Purdiaea), or inflexed in bud; filantherous (the filaments sometimes flattened and petaloid). Anthers dorsifixed; becoming inverted during development, their morphological bases ostensibly apical in the mature stamens (in Purdiaea), or not becoming inverted during development (in the other genera the filaments attached dorsally in Cyrilla and Cliftonia, but ventrally in Purdiaea); versatile; dehiscing via pores (these apical, in Purdiaea), or dehiscing via short slits, or dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with more than one middle layer (2 or 3). Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3(–4) aperturate; colporate; 2-celled.
Gynoecium 2–5 carpelled. Carpels reduced in number relative to the perianth to isomerous with the perianth. The pistil 2–5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2–5 locular. Gynoecium shortly non-stylate, or stylate. Styles when detectable, 1; attenuate from the ovary; apical. Stigmas dry type; non-papillate; Group IV type. Placentation axile to apical. Ovules 1–3 per locule; pendulous (sometimes from a pendulous, stalklike placenta); orthotropous (Purdiaea), or anatropous (Thomas 1960); unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type (from normal embryo sacs, but Hieracium-type from the aposporous embryo sacs in Cliftonia). Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating. Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar.
Fruit fleshy, or non-fleshy; indehiscent; capsular-indehiscent, or a samara, or a drupe. Seeds copiously endospermic; without a testa. Embryo well differentiated. Cotyledons 2 (small). Embryo straight.
Physiology, phytochemistry. Not cyanogenic. Alkaloids absent (3 species). Iridoids not detected. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol, quercetin, and myricetin. Ellagic acid faintly present (Cyrilla). Aluminium accumulation not found.
Geography, cytology. Neotropical. Sub-tropical to tropical. Southeast U.S.A., Central and tropical South America. X = 10.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgrens Superorder Corniflorae; Ericales. Cronquists Subclass Dilleniidae; Ericales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 13. Genera 3; Cliftonia, Cyrilla, Purdiaea.
General remarks. See Thomas 1960.
Economic uses, etc. Leatherwood (Cyrilla) and buckwheat tree (Cliftonia) are cultivated for fragrant flowers and showy autumn foliage.
Illustrations. • Technical details: Cyrilla. • Technical details: Cliftonia (Lindley). • Purdiaea nutans: Hooker, London J. Bot. 5 (1846). • Cyrilla racemiflora (as I. virginica), with Itea spinosa: Bot Mag. 42 (1815, N 1767) and 50 (1823, N 2409).
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: 13th March 2017. delta-intkey.com/angio’.