The families of flowering plants
Habit and leaf form. Herbs. More or less normal plants (but achlorophyllous). Leaves much reduced. Plants succulent; totally parasitic. Parasitic on roots of the host (of shrubby Compositae, Clematis, Euphorbia, etc.). Leaves small; alternate; spiral; membranous (reduced to short scales); simple. Lamina entire. Leaves exstipulate.
Leaf anatomy. Hairs present; glandular (these with a unicellular or uniseriate stalk and an enlarged, bladder-like terminal cell or occasionally a 4-celled head), or eglandular and glandular (?).
Axial (stem, wood) anatomy. Primary vascular tissues comprising a ring of bundles; collateral. Cortical bundles present (leaf traces). Secondary thickening absent. The axial xylem with vessels, or without vessels (Lennoa).
The vessel end-walls when present, simple (circular). The axial xylem with tracheids (in the absence of vessels, in Lennoa).
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in inflorescences; in panicles, or in heads, or in spikes. Inflorescences dense compound spikes, thyrses or discoid heads; with involucral bracts, or without involucral bracts; pseudanthial, or not pseudanthial. Flowers bracteate; regular, or somewhat irregular; if irregular, slightly zygomorphic; 5–10 merous; cyclic; tetracyclic, or pentacyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 10–20; 2 whorled; more or less isomerous. Calyx 5–10; 1 whorled; gamosepalous (but only slightly so, at the most), or polysepalous (the sepals narrow). Calyx lobes markedly longer than the tube. Calyx unequal but not bilabiate to regular; persistent. Corolla 5–10; 1 whorled; gamopetalous; induplicate valvate, or imbricate; hypocrateriform, or tubular; persistent.
Androecium 5–10. Androecial members adnate; free of one another; 1–2 whorled. Androecium exclusively of fertile stamens. Stamens 5–10; inserted in the throat of the corolla tube (at the throat of the corolla, below its mouth); isomerous with the perianth; oppositisepalous; shortly filantherous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium not developing fibrous thickenings. Anther epidermis persistent. Anther wall initially with one middle layer. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; 3–4(–5) aperturate, or 6–8(–10) aperturate; colporate, or colpate and colporate (often with alternating aperturate and inaperturate colpi); 2-celled.
Gynoecium 6–14 carpelled. Carpels reduced in number relative to the perianth to increased in number relative to the perianth. The pistil 12–28 celled (each of the primary locules being divided into two locelli, by a median false septum). Gynoecium syncarpous; eu-syncarpous; superior. Ovary primarily 6–14 locular. Locules secondarily divided by false septa. Gynoecium stylate. Styles 1; apical. Stigmas 1 (capitate or lobed). Placentation axile. Ovules 2 per locule (primarily, i.e. with one per locellus); more or less horizontal; anatropous; unitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped. Endosperm formation cellular. Embryogeny caryophyllad.
Fruit fleshy, or non-fleshy; eventually dehiscent; a capsule (drupaceous). Capsules irregularly circumscissile. Seeds copiously endospermic. Endosperm not oily (starchy). Seeds minute. Seeds with starch. Embryo rudimentary at the time of seed release. Embryo globose.
Physiology, phytochemistry. Aluminium accumulation not found.
Geography, cytology. Neotropical. Temperate to sub-tropical. Southwest U.S.A., Mexico, Colombia. X = 9.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgrens Superorder Solaniflorae; Boraginales, or Solanales (?). Cronquists Subclass Asteridae; Lamiales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order unassigned (as a synonym of Boraginaceae).
Species 5. Genera 3; Ammobroma, Lennoa, Pholisma.
General remarks. While credibly regarded as close to Boraginaceae (q.v.), these achlorophyllous parasitic plants with reduced leaves, cortical stem bundles and no secondary thickening, modified embryology, etc., differ further from Boraginaceae sensu stricto in conspicuous gynoecium and fruit characters.
Illustrations. • Pholisma arenarium: Hook. Ic. Pl. 7 (1844). • Technical details: Pholisma (Hutchinson).
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: 19th October 2016. delta-intkey.com’.