Family Orobanchaceae
Orobanchaceae Vent.~ Scrophulariaceae Including Aeginetiaceae Livers, Phelypaeaceae Horan., Syndiaspermaceae Dulac Habit and leaf form. Achlorophyllous herbs. More or less ‘normal’ plants. Leaves much reduced, or absent. Plants more or less succulent; more or less totally parasitic. Parasitic on roots of the host. Annual, or biennial, or perennial; with neither basal nor terminal aggregations of leaves; commonly rhizomatous, or tuberous (with scaly rhizomes bearing rootlets which are swollen where attached to roots of host plants, in Lathraea, or with underground tubers attached to the roots of host plants, in Orobanche). Mesophytic. Leaves small; alternate; spiral; membranous; sessile; non-sheathing; simple. Lamina entire; lanceolate, or oblong to ovate. Leaves exstipulate. Lamina margins entire. Leaf anatomy. Hydathodes present (occasionally), or absent. The mesophyll with sclerencymatous idioblasts, or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Lathraea, Orobanche). Stem anatomy. Nodes unilacunar. Primary vascular tissue comprising a ring of bundles, or in two or more rings of bundles. Medullary bundles present, or absent. Secondary thickening absent (?). Vessel end-walls simple. Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous. Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes and in spikes. The ultimate inflorescence unit racemose. Inflorescences terminal; usually spikes, rarely racemes. Flowers bracteate (one flower in the axil of each scale); small to medium-sized; very irregular. The floral irregularity involving the perianth and involving the androecium. Flowers cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present (fleshy). Perianth with distinct calyx and corolla; (6–)8, or 10; 2 whorled; isomerous (usually), or anisomerous. Calyx 4–5 (fid), or 2 (the four sepals sometimes more or less united into a lateral pair); 1 whorled; gamosepalous; blunt-lobed, or toothed (or variously split); unequal but not bilabiate, or bilabiate; persistent; valvate, or open in bud. Corolla 5; 1 whorled; gamopetalous (the tube often curved); imbricate (the adaxial members internal); unequal but not bilabiate to bilabiate; persistent. Androecium 4, or 5. Androecial members adnate (epipetalous); markedly unequal; free of one another; 1 whorled. Androecium exclusively of fertile stamens, or including staminodes. Staminodes when present, 1; in the same series as the fertile stamens; representing the posterior median member. Fertile stamens representing the posterior-lateral pair and the anterior-lateral pair. Stamens 4; inserted near the base of the corolla tube, or midway down the corolla tube (below the middle); didynamous; reduced in number relative to the adjacent perianth (the posterior androecial member being absent or staminodal); oppositisepalous; alternating with the corolla members. Anthers cohering, or separate from one another; dorsifixed; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate; appendaged (the connective sometimes spurred at the top), or unappendaged. Endothecium developing fibrous thickenings (usually), or not developing fibrous thickenings (Cistanche). Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate. Anther wall initially with one middle layer, or initially with more than one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate, or nonaperturate (occasionally); 3 aperturate; colpate, or colporate (or colporoidate, or ‘more or less irregular’); 2-celled. Gynoecium 2 carpelled (usually), or 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous; superior. Ovary 1 locular. Gynoecium usually median. The ‘odd’ carpel (when G3) posterior. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 2–4 lobed; dry type; papillate; Group II type. Placentation parietal (the placentas sometimes branched). Ovules in the single cavity 12–100 (‘many’); non-arillate; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; persistent. Synergids hooked (sometimes with filiform apparatus). Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar (the latter the more aggressive). Embryogeny onagrad. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal, or valvular. Fruit 12–100 seeded (‘many’). Seeds endospermic. Endosperm oily. Seeds minute. Seeds with starch. Embryo rudimentary at the time of seed release, or weakly differentiated. Cotyledons 2 (very reduced but detectable, in Lathraea). Embryo achlorophyllous (1/1). Seedling. Germination cryptocotylar. Physiology, biochemistry. Not cyanogenic. Alkaloids present, or absent. Iridoids detected. Verbascosides detected (Cistanche, Orobanche). Proanthocyanidins absent. Flavonols absent. Ellagic acid absent (one Lathraea species). Saponins/sapogenins absent. Aluminium accumulation not found. Geography, cytology. Temperate to tropical. Cosmopolitan, except Eastern South America, Eastern Australia and New Zealand. X = 12, 18–21. Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Lamiiflorae; Scrophulariales. Cronquist’s Subclass Asteridae; Scrophulariales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Lamiales. Species 180. Genera 15; Aeginetia, Boschniakia, Christisonia, Cistanche, Conopholis, Epifagus, Gleadovia, Kopsiopsis, Lathraea (or Scophulariaceae?), Mannafettaea, Necranthus, Orobanche, Phacellanthus, Phelypaea, Platypholis, Xylanche. Illustrations. |
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