The families of flowering plants
~ Orchidaceae but usefully distinguished.
Habit and leaf form. Herbs. Plants more or less succulent, or non-succulent. Perennial; with a basal aggregation of leaves, or without conspicuous aggregations of leaves; rhizomatous. Self supporting (mostly terrestrial). Leaves alternate; spiral, or distichous; herbaceous, or fleshy; petiolate to sessile; sheathing. Leaf sheaths tubular. Leaves simple. Lamina entire; linear to ovate; parallel-veined; without cross-venules. Leaves eligulate. Lamina margins entire. Vernation conduplicate, or plicate.
General anatomy. Plants with silica bodies (in idioblasts termed stegmata, in the leaves).
Leaf anatomy. The leaf lamina dorsiventral. Epidermis containing silica bodies, or without silica bodies (?). Stomata present; anomocytic, or paracytic. Guard-cells not grass type. The mesophyll containing crystals. The crystals raphides. Foliar vessels absent.
Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.
Root anatomy. Roots with velamen (commonly), or without velamen (?). Root xylem with vessels, or without vessels; vessel end-walls simple.
Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in inflorescences; when aggregated, in racemes. The ultimate inflorescence units racemose. Inflorescences scapiflorous, or not scapiflorous; terminal; terminal racemes, or sometimes one-flowered. Flowers medium-sized, or large; very irregular; zygomorphic; resupinate. The floral irregularity involving the perianth and involving the androecium. Flowers cyclic; basically pentacyclic. Perigone tube absent.
Perianth with distinct calyx and corolla, or of tepals (usually, though very zygomorphic and the inner median very different in form from the rest); 5 (in that the lateral sepals are fused into a synsepalum), or 6 (if the synsepalum is counted as two); partially joined (the outer laterals); 2 whorled; isomerous (if the joined, outer laterals interpreted as two), or anisomerous (if not); if not readily resolvable into calyx and corolla, petaloid; without spots, or spotted; different in the two whorls (the lateral petals often much longer than the other tepals, and the median petal the labellum characteristically slipper-shaped); of various colours. Tepal apex trichomes (TAT) absent (Paphiopedilum). Calyx 2, or 3 (i.e. basically three, with the laterals joined); 1 whorled; partially gamosepalous (the anterior member opposite the labellum free). 2 of the members joined (the laterals). Calyx morphologically with the median member anterior (but the flower usually resupinate, so ostensibly posterior). Corolla 3; 1 whorled; polypetalous.
Androecium 3. Androecial members free of the perianth; united with the gynoecium (the filaments and style forming a thick, inflexed gynostemium); coherent (via the gynostemium); theoretically 2 whorled (the two fertile members supposedly representing the inner whorl, the staminodium the median of the outer whorl). Androecium including staminodes. Staminodes 1 (the median member of the outer whorl); theoretically external to the fertile stamens; non-petaloid (shieldlike). Stamens 2 (morphologically anterior, opposite the labellum, supposedly the laterals of the inner whorl); reduced in number relative to the adjacent perianth; (at least theoretically) oppositiperianthial. Anthers dehiscing via longitudinal slits; latrorse. The endothecial thickenings spiral. Microsporogenesis simultaneous. Tapetum glandular. Pollen shed as single grains (usually, but more or less viscid), or shed in aggregates (rarely); when aggregated, in the form of pollinia (these very rare). Pollen grains aperturate; sulcate, or ulcerate, or porate; 2-celled.
Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 1 celled, or 3 celled. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary 1 locular, or 3 locular. The odd carpel anterior. Gynoecium stylate. Styles 1; apical. Stigmas 1; usually 3 lobed; wet type. Placentation when unilocular, parietal; when trilocular, axile. Ovules not differentiated; in the single cavity 50–200 (or more many); 30–50 per locule (or more); non-arillate; anatropous; bitegmic (usually), or unitegmic (e.g. Paphiopedilum); tenuinucellate. Embryo-sac development arrested until after fertilization. Endosperm formation nuclear (arrested early). Embryogeny onagrad and asterad.
Fruit non-fleshy; dehiscent; a capsule; 50–200 seeded (or more). Seeds non-endospermic; minute to small. Embryo rudimentary at the time of seed release. Embryo achlorophyllous (Cypripedium sp.).
Seedling. Seedling collar not conspicuous. Coleoptile absent. Primary root ephemeral.
Physiology, phytochemistry. Not cyanogenic. Alkaloids present (rarely?), or absent. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent.
Geography, cytology. Temperate, sub-tropical, and tropical. North boreal and north temperate, old and new world tropics except Africa.
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Orchidales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Asparagales (as a synonym of Orchidaceae).
Species 99. Genera 4; Cypripedium, Paphiopedilum, Phragmipedium, Selinipedium.
General remarks. Seemingly differing from Orchidaceae sensu stricto (q.v.) in the xylem lacking vessels and the achlorophyllous embryo, as well as the six conspicuous androecium characters.
Illustrations. • Technical details: Cypripedium. • Cypripedium calceolus (B. Ent., 1832).
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: 20th July 2017. delta-intkey.com/angio’.