The families of flowering plants.
IncludingHydrocereae (Hydroceraceae) Bl., Impatientaceae Barnhart
Habit and leaf form. Herbs (generally with translucent stems, rarely almost shrubby); with watery juice. Plantsmore or less succulent. Annual, or perennial; with a basal aggregation of leaves, or with neither basal nor terminal 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. Hydathodes commonly present. Stomata present; anomocytic, or anisocytic. Hairs usually absent.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals raphides. Minor leaf veins with phloem transfer cells (Impatiens).
Stem anatomy. Nodes unilacunar. Primary vascular tissue comprising a ring of bundles. Secondary thickening absent. Xylem with vessels. Vessel end-walls simple. Sieve-tube plastids S-type.
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 unit (when flowers aggregated) 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.
Perianthwith 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. Anthersconnivent, 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.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (one species). Proanthocyanidins present, or absent; when present, cyanidin, or cyanidin and delphinidin. Flavonols present; kaempferol, or kaempferol and quercetin. Ellagic acid absent (Impatiens). Saponins/sapogenins absent. C3. C3 physiology recorded directly in Impatiens.
Geography, cytology. Holarctic, Paleotropical, and Cape. Temperate to tropical. Eurasia, Africa, North America.X = 6–11.
Taxonomy.Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Rutiflorae; Balsaminales. Cronquist’s Subclass Rosidae; Geraniales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Ericales.
Species 600. Genera 4; Hydrocera, Impatiens, Impatientella, Semeiocardium.
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