The families of flowering plants
Including Hydrocereae (Hydroceraceae) Bl., Impatientaceae Barnhart
Habit and leaf form. Herbs (generally with translucent stems, rarely almost shrubby); with watery juice. Plants more or less succulent. Annual, or perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves. Helophytic, or mesophytic. Leaves medium-sized; alternate, or opposite, or whorled; when alternate, spiral; when whorled, 3 per whorl; flat; petiolate; non-sheathing; simple; epulvinate. Lamina entire; acicular to linear, or oblong to ovate; pinnately veined; cross-venulate. Leaves exstipulate (as generally interpreted), or stipulate. Stipules if detectable, represented by glands. Lamina margins entire, or crenate, or serrate.
Leaf anatomy. The leaf lamina dorsiventral. Hydathodes commonly present (in te leaf teeth). Stomata present; anomocytic, or anisocytic. Hairs usually absent. The mesophyll containing mucilage cells, or not containing mucilage cells; containing crystals. The crystals raphides (the abundance of raphide sacs - these often also containing mucilage - here and in the cortex being characteristic of the family). Minor leaf veins with phloem transfer cells (Impatiens).
Axial (stem, wood) anatomy. Young stems with solid internodes, or with hollow internodes. Secretory cavities absent (but large cells with mucilaginous contents in the ground parenchyma). Nodes unilacunar. Primary vascular tissues comprising a ring of bundles; collateral. Internal phloem absent. Cortical bundles absent. Medullary bundles absent. Secondary thickening more or less absent to developing from a conventional cambial ring (the interfascicular cambium giving rise internally only to thin-walled ground tissue, without vessels). The axial xylem with vessels.
The vessel end-walls simple.
Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous; mechanism conspicuously specialized (as regards the androecium/gynoecium relationship).
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in inflorescences; when aggregated, in cymes. The ultimate inflorescence units cymose. Inflorescences or flowers axillary; small, sometimes umbelliform cymes, or the flowers solitary. Flowers bracteate; bracteolate, or ebracteolate; medium-sized; very irregular; zygomorphic; resupinate (often, the anterior organs appearing posterior and the large, spurred posterior sepal appearing anterior in the mature flower), or not resupinate. The floral irregularity involving the perianth and involving the androecium. Flowers basically 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 2 whorled; isomerous, or anisomerous; different in the two whorls. Calyx 5, or 3 (often coloured, the 208,8/10 morphologically anterior pair reduced or missing, the two laterals small and displaced forward to the anterior aspect of the flower, the posterior large and heavy); 1 whorled; polysepalous; unequal but not bilabiate; usually spurred (via the large member); not persistent (caducous); imbricate; with the median member posterior (before resupination). Corolla 5 (but often simulating three by fusion of the lateral pairs to form two equally or unequally bilobed petals); 1 whorled; polypetalous (Hydrocera), or partially gamopetalous (Impatiens). 4 of the petals joined (the large, morphologically anterior member remaining distinct, the latero-posterior members joined to form two compound petals). The joined petals latero- posterior (before resupination). Corolla imbricate; unequal but not bilabiate.
Androecium 5. Androecial members free of the perianth; free of the gynoecium (but connate around it, forming a deciduous calyptra); markedly unequal; coherent (the short, broad filaments free below but connate above); 1 adelphous; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers connivent, or cohering (around the top of the ovary); ultimately rupturing at the base, and lifted away as a calyptra by the elongating pistil; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate, or 4–5 aperturate; colpate; 2-celled.
Gynoecium 5 carpelled. Carpels isomerous with the perianth. The pistil 5 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior. Ovary 5 locular. Gynoecium non-stylate (the stigma almost sessile), or stylate (the style very short). Styles 1; apical. Stigmas 1, or 5; wet type; non-papillate; Group IV type. Placentation axile. Ovules 2–3 per locule (Hydrocera), or 5–50 per locule (numerous, in Impatiens); funicled; pendulous; apotropous; with dorsal raphe; superposed (in one series); anatropous; bitegmic, or unitegmic (by fusion); tenuinucellate. Outer integument not contributing to the micropyle. Endothelium differentiated. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar (the latter much the stronger). Embryogeny onagrad.
Fruit fleshy (Hydrocera), or non-fleshy (Impatiens); dehiscent, or indehiscent; a capsule (Impatiens), or a drupe (berry-like, in Hydrocera). Capsules of Impatiens loculicidal. Fruit of Impatiens elastically dehiscent. Seeds non-endospermic (or scantily endospermic, in Impatiens). Embryo well differentiated. Cotyledons 2 (expanded); plano-convex. Embryo achlorophyllous (1/2); straight.
Seedling. Germination phanerocotylar.
Physiology, phytochemistry. C3. C3 physiology recorded directly in Impatiens. Not cyanogenic. Alkaloids absent (one species). Saponins/sapogenins absent. Proanthocyanidins present, or absent; when present, cyanidin, or cyanidin and delphinidin. Flavonols present; kaempferol, or kaempferol and quercetin. Ellagic acid absent (Impatiens). Sieve-tube plastids S-type.
Geography, cytology. Holarctic, Paleotropical, and Cape. Temperate to tropical. Eurasia, Africa, North America. X = 6–11.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgrens Superorder Rutiflorae; Balsaminales. Cronquists Subclass Rosidae; Geraniales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 600. Genera 4; Hydrocera, Impatiens, Impatientella, Semeiocardium.
Illustrations. • Technical details: Impatiens. • Technical details: Impatiens (Lindley). • Impatiens roylei: as I. granduligera, Bot. Reg. xxvi, 22 (1840). • Impatiens roylei var. candida: as I. candida, Bot. Reg. 20, 1841. • Impatiens scabrida: as I. tricornis, Bot. Reg. xxvi, 9 (1840). • Impatiens noli-tangere (as I. noli-me-tangere), I. capensis (as I. fulva) and I. parviflora: Eng. Bot. 313–315, 1864. • Hydrocera triflora: Fl. China (2007).
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: 12th September 2017. delta-intkey.com/angio’.