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 with neither basal nor terminal 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. Epidermis containing silica bodies, or without silica bodies (?). Stomata present; anomocytic, or paracytic. Guard-cells not ‘grass type’.
Lamina dorsiventral. The mesophyll containing calcium oxalate crystals. The mesophyll crystals raphides. Vessels absent.
Stem anatomy. Secondary thickening absent. 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 unit 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. 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, biochemistry. Not cyanogenic. Alkaloids present (rarely?), or absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent. Saponins/sapogenins 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.
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