Monotropaceae Nutt.
~ Pyrolaceae
Including Hypopitydaceae Link
Habit and leaf form. Herbs. More or less ‘normal’ plants. Leaves much reduced. Plants more or less succulent; saprophytic (without chlorophyll). Perennial; with neither basal nor terminal aggregations of leaves; rhizomatous. Mesophytic. Leaves small; alternate; spiral; membranous; sessile; non-sheathing; simple; epulvinate. Lamina entire; with greatly reduced vascular tissue. Leaves exstipulate. Lamina margins entire.
Stem anatomy. Nodes unilacunar. Secondary thickening absent (the vascular system reduced). Xylem without vessels.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes and in racemes. The terminal inflorescence unit cymose, or racemose. Inflorescences racemes, thyrses or heads; with involucral bracts, or without involucral bracts. Flowers bracteate; small to medium-sized; regular; cyclic; tetracyclic, or pentacyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal; lobed.
Perianth with distinct calyx and corolla (usually), or sepaline (corolla rarely absent); 4–12; 2 whorled (usually), or 1 whorled; isomerous. Calyx (2–)4–5(–6) (sometimes not clearly distinguishable from bracts); 1 whorled; polysepalous, or gamosepalous (sometimes basally connate). Calyx lobes markedly longer than the tube. Calyx regular; imbricate. Corolla when present, (3–)5(–6); 1 whorled; polypetalous, or gamopetalous; imbricate, or contorted; regular.
Androecium 6–12 (often twice C). Androecial members free of the perianth; free of one another, or coherent (the filaments sometimes basally connate); when connate, 1 adelphous; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 6–12; diplostemonous (often), or isomerous with the perianth. Anthers becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; dehiscing via pores to dehiscing via short slits (often), or dehiscing via longitudinal slits, or dehiscing transversely; finally introrse (inverting during development); unilocular (when transversely dehiscent), or bilocular; tetrasporangiate. Endothecium not developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads isobilateral, or decussate. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; (2–)3–4(–5) aperturate; colpate, or colporate (col(por)oidate, occasionally rupate); 2-celled.
Gynoecium (4–)5(–6) carpelled. The pistil 1 celled, or (4–)5(–6) celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary (4–)5(–6) locular, or 1 locular. Gynoecium stylate. Styles 1; apical. Stylar canal present. Stigmas 1; capitate. Placentation when unilocular, parietal; axile, or parietal (when the placentas fall short of the middle). Ovules in the single cavity (when unilocular) 12–100 (‘many’); 12–50 per locule (‘many’); non-arillate; anatropous; unitegmic; tenuinucellate. Embryo-sac development Polygonum-type, or Allium-type. Antipodal cells formed; 3; not proliferating; persistent. Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar. Embryogeny caryophyllad.
Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule (usually), or a berry. Capsules loculicidal. Fruit 20–100 seeded (‘many’). Seeds endospermic. Perisperm absent. Seeds minute. Embryo rudimentary at the time of seed release. Embryo achlorophyllous (1/1).
Physiology, biochemistry. Not cyanogenic. Iridoids detected; ‘Route I’ type (normal?). Ellagic acid absent. Arbutin present. Andromedotoxin recorded. Sugars transported as oligosaccharides + sucrose.
Geography, cytology. Temperate (and tropical mountains). Widespread, temperate and tropical mountains. X = 8.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Ericales. Cronquist’s Subclass Dilleniidae; Ericales. APG (1998) Eudicot; core Eudicot; Asterid; unassigned to Euasterid I or Euasterid II; Ericales (as a synonym of Ericaceae). Species 15. Genera 10; Allotropa, Cheilotheca, Hemitomes, Monotropa, Monotropastrum, Monotropsis, Pityopus, Pleuricospora, Pterospora, Sarcodes.
Illustrations. • Technical details (Monotropa).
Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References).
