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The families of flowering plants

L. Watson and M.J. Dallwitz

Spigeliaceae Mart.

~ Loganiaceae sensu lato, Strychnaceae.

Habit and leaf form. Herbs (rarely subshrubs). ‘Normal’ plants, or switch-plants; the switch forms with the principal photosynthesizing function transferred to stems. Leaves well developed, or much reduced. Annual, or perennial. Mesophytic. Leaves opposite, or opposite and whorled (often in false whorls towards the stem tips); ‘herbaceous’, or leathery (?), or membranous; petiolate to subsessile; connate, or not connate (connected by an interpetiolar line or small stipules); simple. Lamina entire; pinnately veined, or palmately veined (rarely); cross-venulate. Leaves stipulate, or exstipulate (then the members of the leaf pair connected by an interpetiolar line). Stipules when detectable, interpetiolar (small); with colleters. Lamina margins entire. Leaf development not ‘graminaceous’.

Leaf anatomy. Extra-floral nectaries absent. Hairs present, or absent; eglandular. Complex hairs present, or absent; stellate (occurring in several species). Minor leaf veins without phloem transfer cells (Spigelia).

Axial (stem, wood) anatomy. Young stems cylindrical. Internal phloem present. Secondary thickening anomalous. The anomalous secondary thickening from a single cambial ring. Primary medullary rays narrow (uniseriate).

The wood diffuse porous. The vessel end-walls oblique; simple (mostly), or reticulately perforated (occasional, irregular). The vessels without vestured pits. The axial xylem with fibre tracheids. The parenchyma absent. ‘Included’ phloem present. The wood not storied.

Reproductive type, pollination. Plants hermaphrodite; homostylous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, in spikes, in umbels, and in fascicles. The ultimate inflorescence units cymose. Inflorescences terminal, or axillary; usually cincinnous, variously cymes or unilateral spikes, fasciculate or subumbellate. Flowers regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous; regular; persistent. Corolla 5; 1 whorled; gamopetalous (not internally hairy). Corolla lobes markedly shorter than the tube. Corolla valvate (the lobes pointed, erect); funnel-shaped, or hypocrateriform, or tubular; regular; yellow, or red, or pink, or purple.

Androecium 5. Androecial members adnate (to the corolla tube); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 5; inserted midway down the corolla tube, or in the throat of the corolla tube; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; introrse. Tapetum glandular. Pollen grains aperturate; (2–)3(–4) aperturate; colporate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2 locular; sessile. Gynoecium stylate. Styles 1 (the upper half often deciduous); attenuate from the ovary, or from a depression at the top of the ovary (?); apical. Stigmas 1; truncate, or clavate, or capitate. Placentation axile (the placentas peltate). Ovules differentiated; 10–50 per locule (‘many’); anatropous, or campylotropous, or hemianatropous (?); unitegmic; tenuinucellate. Endothelium not differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Endosperm formation nuclear. Endosperm haustoria present, or absent; lateral. Embryogeny solanad.

Fruit non-fleshy; not an aggregate (but more or less didymous); dehiscent; a capsule (compressed contrary to the septum). Capsules circumscissile (the cupular base remaining in the persistent calyx). Fruit 5–15 seeded (‘few’). Seeds endospermic. Endosperm ruminate. Seeds wingless (and not particularly compressed, sometimes polyhedral). Embryo straight.

Physiology, phytochemistry. Alkaloids present. Verbascosides not detected. Cornoside not detected. Iridoids not detected.

Geography, cytology. Holarctic and Neotropical. Sub-tropical to tropical. Warm North to tropical South America. 2n = 26, 32, 48, 64. Supposed basic chromosome number of family: 8 and 13 (?). Ploidy levels recorded: 2, 4, and 6.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Gentianiflorae; Gentianales. Cronquist’s Subclass Asteridae; Gentianales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; lamiid; Order Gentianales (as a synonym of Loganiaceae).

Species 50. Genera 1; Spigelia.

General remarks. See Leeuwenberg 1980, under Loganiaceae. Comparisons amongst the descriptions compiled here do not support including Spigelia in Strychnaceae, as proposed by Struwe and Albert (1994). Its nearest neighbours in these terms are Solanaceae, followed by Loganiaceae sensu stricto, Antoniaceae, Gentianaceae, Mitreolaceae, Rubiaceae (etc.). Other than ‘esoteric characters’ depending on restricted sampling (wood anatomy, seeds with ruminate endopsperm, no iridoids), Spigelia appears to differ from Loganiaceae sensu stricto only in the valvate corolla and circumscissle capsules. See comments under Loganiaceae.

Illustrations. • Spigelia marilandica: Barton, Veg. Materia Medica (1818). • Spigelia marilandica: Bot. Mag. 80, 1789. • Spigelia marilandica: Bot. Mag. 80, text. • Spigelia pulchellas: Martius, Nova Gen. et Spec. Pl. Brasiliensium 2 (1826).

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: 20th July 2017.’.