The families of flowering plants
Including Arceuthobiaceae Van Tiegh., Bifariaceae Nakai, Ginalloaceae Van Tiegh. ex Nakai, Razoumofskyaceae Van Tiegh.
Habit and leaf form. Chlorophyllous but parasitic shrubs. Normal plants, or switch-plants; sometimes with the principal photosynthesizing function transferred to stems. Leaves well developed, or much reduced. Plants rootless (in the normal sense with haustoria); partially parasitic. Parasitic on aerial parts of the host. Stem growth conspicuously sympodial (often pseudodichotomous), or not conspicuously sympodial. Mesophytic, or xerophytic. Leaves opposite; herbaceous, or leathery, or membranous; simple. Lamina entire; one-veined, or parallel-veined. Leaves exstipulate.
Leaf anatomy. Minor leaf veins without phloem transfer cells (Arceuthobium).
Stem anatomy. Secretory cavities present, or absent. Secondary thickening developing from a conventional cambial ring (?). Xylem with libriform fibres; with vessels. Vessel end-walls simple.
Reproductive type, pollination. Plants monoecious, or dioecious, or polygamomonoecious (?). Pollination anemophilous, or entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary to aggregated in inflorescences; in cymes, or in racemes, or in spikes. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; (1-)3-flowered dichasia in spikes or branched inflorescences. Flowers bracteate; minute to small; regular; cyclic.
Perianth sepaline, or petaline, or vestigial (often represented by mere bumps or teeth on the ovary rim); (2–)3, or 4; free, or joined; 1 whorled; persistent, or deciduous (e.g. caducous in female Viscum). Calyx (if P so interpreted) (2–)3, or 4 (females often 3, males 4); 1 whorled; polysepalous, or partially gamosepalous, or gamosepalous; entire, or lobulate, or blunt-lobed, or toothed; regular; persistent, or not persistent; valvate, or open in bud.
Androecium 4. Androecial members free of the perianth, or adnate (to the perianth); all equal; free of one another, or coherent (via the anthers); 1 whorled. Androecium exclusively of fertile stamens. Stamens (2–)4; isomerous with the perianth; oppositisepalous; filantherous, or with sessile anthers. Anthers separate from one another, or cohering (e.g. Korthalsella having a synandrium); dehiscing via pores, or dehiscing via short slits, or dehiscing via longitudinal slits, or dehiscing transversely; introrse; unilocular to many locular; bisporangiate, or tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. Anther wall initially with one middle layer, or initially with more than one middle layer; of the monocot type. Tapetum glandular. Pollen grains aperturate; 3 aperturate; 2-celled (in 3 genera).
Gynoecium 3 carpelled, or 4 carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; eu-syncarpous; inferior. Ovary 1 locular. Gynoecium non-stylate, or non-stylate to stylate, or stylate. Styles 1; apical. Placentation basal (i.e. with a short placental column). Ovules not differentiated; in the single cavity 2; sessile; orthotropous; without integuments (the ovules being scarcely developed). Embryo-sac development Allium-type. Polar nuclei fusing prior to fertilization. Endosperm formation cellular. Embryogeny often by transverse cleavage.
Fruit fleshy; indehiscent; a berry (with viscous tissue within); elastically dehiscent (sometimes), or passively dehiscent; 1(–2) seeded. Seeds endospermic; without a testa. Embryo weakly differentiated. Cotyledons 2. Embryo chlorophyllous (2/2).
Physiology, biochemistry. Not cyanogenic. Alkaloids present (Viscum, Phoradendron). Proanthocyanidins present, or absent (Viscum); cyanidin and delphinidin (Arceuthobium). Flavonols present, or absent; quercetin and myricetin. Ellagic acid absent (Arceuthobium, Viscum). Arbutin absent. Saponins/sapogenins absent. Aluminium accumulation not found.
Geography, cytology. Temperate to tropical. Cosmopolitan, especially tropical and warm regions. X = 10–14 (polyploidy rare).
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgrens Superorder Santaliflorae; Santalales. Cronquists Subclass Rosidae; Santalales. APG 3 core angiosperms; core eudicot; Superorder Santalanae; Order Santalales (as a synonym of Santalaceae).
Species 450. Genera 7; Arceuthobium, Dendrophthora, Ginalloa, Korthalsella, Notothixos, Phoradendron, Viscum.
Economic uses, etc. Viscum album and Phoradendron flavescens are the Yuletide mistletoes.
Illustrations. • Technical details: Arceuthobium, Viscum. • Technical details: Viscum. • Viscum album (B. Ent.).
The trees, though
summer, yet forlorn and lean,
Oercome with moss, and baleful mistletoe
(Titus Andronicus, ii., 3)
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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).
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 19th December 2012. http://delta-intkey.com’.