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The families of flowering plants

L. Watson and M.J. Dallwitz

Orobanchaceae Vent.

~ Scrophulariaceae.

Including Aeginetiaceae Livers, Phelypaeaceae Horan., Syndiaspermaceae Dulac

Habit and leaf form. Achlorophyllous herbs. Leaves much reduced (to scales), or absent. Plants rather succulent, or non-succulent; parasitic; mycoheterotrophic; not green; parasitic on roots of the host. Annual, or biennial, or perennial; without conspicuous 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. Stomata usually present (sometimes incompletely developed). Hairs present; eglandular, or eglandular and glandular (the former scarce, when present simple; the latter usually numerous, with stalks of (1-)2-several cells, sometimes branched, their glandular heads dividing by vertical and periclinal walls and secreting oil between the outer wall and the uplifted cuticle; peltate glands rare, recorded in Christisonia). Adaxial hypodermis present (rarely), or absent. The mesophyll with sclerenchymatous idioblasts (in Conopholis), or without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Lathraea, Orobanche).

Axial (stem, wood) anatomy. Cork cambium probably absent. Nodes unilacunar. Primary vascular tissues in a cylinder, without separate bundles (in that the phloem only sometimes forms a ring), or comprising a ring of bundles, or comprising two or more rings of bundles (sometimes exhibiting an inner ring of bundles); collateral. Medullary bundles present (if the inner ring be thus interpreted), or absent. Secondary thickening absent, or developing from a conventional cambial ring (? - the vascular system very reduced).

The 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 units 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; more or less ‘dorsifixed’, or the thecae separate - cf. Scrophulariaceae; 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, phytochemistry. Not cyanogenic. Alkaloids present, or absent. Verbascosides detected (Cistanche, Orobanche). Iridoids detected. Saponins/sapogenins absent. Proanthocyanidins absent. Flavonols absent. Ellagic acid absent (one Lathraea species). 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 III core angiosperms; core eudicot; Superorder Asteranae; lamiid. APG IV Order Lamiales.

Species 180. Genera 15; Aeginetia, Boschniakia, Buchnera, Christisonia, Cistanche, Conopholis, Epifagus, Gleadovia, Kopsiopsis, Lathraea (or Scophulariaceae?), Mannafettaea, Necranthus, Orobanche, Phacellanthus, Phelypaea, Platypholis, Radamaea, Xylanche.

Illustrations. • Cistanche lutea: Thonner. • Le Maout and Decaisne: Lathraea. • Le Maout and Decaisne: Orobanche. • Aphyllon uniflorum (as Anoplanthus): Lindley. • Lathraea squamaria (B. Ent.). • Lathraea squamaria: Eng. Bot. 1006 (1866). • Orobanche alba: as O. rubra, Eng. Bot. 1011 (1866). • Orobanche artemisiae-campestris: as O. picridis, Eng. Bot. 1014, 1866. • Orobanche caryophyllacea: Eng. Bot. 1012, 1866. • Orobanche elatior: Eng. Bot. 1013, 1866. • Orobanche hederae: Eng. Bot. 1015, 1866. • Orobanche minor (photos). • Orobanche minor: as O. eu-minor, Eng. Bot. 1016, 1866. • Orobanche purpurea: as O. caerulea, Eng. Bot. 1000 (1866). • Orobanche ramosa: Eng. Bot. 1007, 1866. • Orobanche minor, O. purpurea (B. Ent. compilation). • Buchnera nigricans, as Stellularia: Hook. Ic. Pl. 14 (1880–82). • Christisonia thwaitesii: Trimen, Ill. Fl. Ceylon (1895). • Leaf hairs of Lathraea squamaria, with Verbascum and Pedicularis (Scrophulariaceae): Solereder, 1908.

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: 15th April 2018.’.