The families of flowering plants
Habit and leaf form. Herbs (with articulated stems); bearing essential oils. Biennial; without conspicuous aggregations of leaves; rhizomatous. Helophytic, or mesophytic. Leaves alternate; spiral to distichous; petiolate; aromatic; simple. Lamina entire; mostly oblong, or ovate; pinnately veined, or palmately veined; cross-venulate; cordate, or rounded at the base. Leaves stipulate. Stipules adnate to the petiole, intrapetiolar. Lamina margins entire.
Leaf anatomy. The leaf lamina dorsiventral. Stomata present; cyclocytic. Adaxial hypodermis present. The mesophyll with spherical etherial oil cells; containing crystals. The crystals druses. Minor leaf veins without phloem transfer cells (Houttuynia).
Axial (stem, wood) anatomy. Nodes with five or more leaf traces. Primary vascular tissues comprising a ring of bundles, or comprising two or more rings of bundles (one ring or sometimes two, the bundles less scattered than in Piperaceae); collateral. Secondary thickening absent.
The vessel end-walls oblique; scalariform.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in racemes, or in spikes. The ultimate inflorescence units racemose. Inflorescences terminal; dense, slender, peduncled spikes or racemes; often with involucral bracts, or without involucral bracts; pseudanthial (often, the lower bracts being sometimes involucral and petaloid), or not pseudanthial. Flowers small; regular; cyclic; bi- or tricyclic. Hypogynous disk absent.
Androecium 3, or 6, or 8. Androecial members united with the gynoecium (to its whole length, or only its base), or free of the gynoecium; free of one another; 1 whorled (when 3), or 2 whorled (when six or eight, then the members alternating). Androecium exclusively of fertile stamens. Stamens 3, or 6, or 8; filantherous (with slender filaments). Anthers basifixed; non-versatile; dehiscing via longitudinal slits; extrorse to latrorse to introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer. Tapetum glandular. Pollen shed as single grains (these small to minute). Pollen grains aperturate, or nonaperturate; when aperturate, 1 aperturate; sulcate (to faintly trichotomosulcate); 2-celled.
Gynoecium 3 carpelled, or 4(–5) carpelled. The pistil 1 celled. Gynoecium apocarpous, or syncarpous; semicarpous (the conduplicate carpels distinct above the connate base, in Saururus), or synovarious (in the other genera); superior (mostly), or inferior (Anemopsis). Carpel of Saururus incompletely closed (by virtue of the style being incompletely closed); stylate (with decurrent stigma); of Saururus (1–)2–4 ovuled. Placentation dispersed (laminar-lateral). Ovary 1 locular. Gynoecium stylate. Styles 3–4(–5); free (and not wholly closed, the stigmas decurrent); in the genera other than Saururus apical. Stigmas 3–4(–5); dry type; papillate; Group II type. Placentation parietal. Ovules in the single cavity 20–40(–50) (610 on each placenta); orthotropous to hemianatropous; bitegmic; tenuinucellate, or crassinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type (monosporic). Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Endosperm formation cellular, or helobial. Endosperm haustoria present; chalazal. Embryogeny asterad.
Fruit somewhat fleshy, or non-fleshy; an aggregate (Saururus), or not an aggregate. The fruiting carpel in Saururus indehiscent; a follicle (semi-succulent). Fruit in the other genera dehiscent, or indehiscent; fleshy, a capsule, or capsular-indehiscent. Capsules when dehiscent, apically valvular. Seeds scantily endospermic. Perisperm present (copious, with clustered starch grains). Seeds with starch. Embryo rudimentary at the time of seed release (minute).
Seedling. Germination phanerocotylar.
Physiology, phytochemistry. C3. C3 physiology recorded directly in Saururus. Accumulated starch other than exclusively pteridophyte type. Cyanogenic (?), or not cyanogenic. Alkaloids absent (one species). Iridoids not detected. Saponins/sapogenins absent. Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (2 genera). Sieve-tube plastids S-type.
Geography, cytology. Holarctic. Temperate to tropical. Eastern Asia, Southern U.S.A. and Mexico. X = 11, 12(?).
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Nymphaeiflorae; Piperales. Cronquists Subclass Magnoliidae; Piperales. APG 3 Order Piperales.
Species 7. Genera 4; Anemopsis, Gymnotheca, Houttuynia, Saururus.
Illustrations. • Houttuynia cordata: Bot. Mag. 54 (1827). • Gymnotheca chinensis: Hook. Ic. Pl. 19 (1889). • Le Maout and Decaisne: Saururus, Gymnotheca, Houttuynia.
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: 24th October 2017. delta-intkey.com/angio’.