Pyrolaceae Dum.
Including Pirolaceae auctt.
Excluding Monotropaceae
Habit and leaf form. Herbs. ‘Normal’ plants (mostly), or switch-plants. Leaves well developed (usually), or much reduced. Plants non-succulent; autotrophic, or saprophytic. Perennial; with a basal aggregation of leaves (often), or with neither basal nor terminal aggregations of leaves; rhizomatous. Leaves unless much reduced, evergreen; alternate, or opposite, or whorled; flat; petiolate; non-sheathing; simple; epulvinate. Lamina entire; one-veined, or pinnately veined (unless much reduced). Leaves exstipulate. Lamina margins entire, or crenate, or serrate, or dentate. Leaves without a persistent basal meristem.
Leaf anatomy. Minor leaf veins without phloem transfer cells (Pyrola).
Stem anatomy. Nodes unilacunar. Secondary thickening absent, or developing from a conventional cambial ring (?). Xylem with vessels, or without vessels (?).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary (Moneses), or aggregated in ‘inflorescences’; when aggrega, in racemes, or in umbels, or in corymbs. The terminal inflorescence unit racemose (Pyrola), or cymose. Inflorescences scapiflorous, or not scapiflorous. Flowers bracteate; ebracteolate; small; regular; (4–)5 merous; cyclic; pentacyclic. Free hypanthium absent. Hypogynous disk present, or absent; when present, intrastaminal; of separate members, or annular.
Perianth with distinct calyx and corolla; 8, or 0; 2 whorled; isomerous. Calyx (4–)5; 1 whorled; polysepalous, or gamosepalous (shortly, basally). Calyx lobes markedly longer than the tube. Calyx regular; persistent; imbricate; with the median member posterior. Corolla (4–)5; 1 whorled; polypetalous (though the primordium annular); imbricate; regular; white, or pink, or purple (or rose). Petals sessile (orbicular).
Androecium 8, or 10. Androecial members free of the perianth; free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 8, or 10; diplostemonous; alternisepalous; both alternating with and opposite the corolla members. Anthers becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; dehiscing via pores (these ostensibly apical); introrse; tetrasporangiate; appendaged (the thecae produced into short tubes), or unappendaged. The anther appendages ostensibly apical. Anther wall initially with one middle layer. Tapetum glandular. Pollen shed in aggregates (nearly always), or shed as single grains; in tetrads (except in Orthilia). Pollen grains aperturate; 3 aperturate; colporate; 2-celled.
Gynoecium (4–)5 carpelled (opposite the petals). Carpels isomerous with the perianth. The pistil (4–)5 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary ostensibly (4–)5 locular (except towards the top). The ‘odd’ carpel anterior. Ovary sessile. Gynoecium stylate. Styles 1; attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary to much longer than the ovary (often declinate). Stylar canal present. Stigmas 1; (4–)5 lobed; capitate to peltate. Placentation axile (ostensibly), or parietal (i.e. the greatly intruded placentas not joined in the middle). Ovules 20–50 per locule (i.e. ‘many’); funicled; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3 (uninucleate); not proliferating. Synergids slender, with broad bases. Endosperm formation cellular. Endosperm haustoria present; chalazal and micropylar (short, 1–celled). Embryogeny caryophyllad.
Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Seeds endospermic; minute, or small; winged (at each end). Embryo rudimentary at the time of seed release. Embryo achlorophyllous (1/1).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Cyanogenic, or not cyanogenic. Iridoids detected; ‘Route I’ type (?normal). Proanthocyanidins present; cyanidin. Flavonols present; kaempferol and quercetin. Ellagic acid absent (one Pyrola species). Arbutin present. Ursolic acid present. Sugars transported as oligosaccharides + sucrose.
Geography, cytology. Holarctic and Neotropical. Frigid zone and temperate (cold), or sub-tropical to tropical (a few only). Cold North temperate and Arctic, Chimaphila extending to Central America and the West Indies. X = 8, 11, 13, 16, 19, 23.
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 30. Genera 3; Chimaphila, Moneses, Pyrola.
Illustrations. • Pyrola media. • Technical details (Pyrola).
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).
