The families of flowering plants.
~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. Leaves without a persistent basal meristem.
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).
Stem anatomy. Young stems cylindrical. Internal phloem present. Secondary thickening anomalous; from a single cambial ring. ‘Included’ phloem present. Xylem with fibre tracheids. Vessel end-walls oblique; simple (mostly), or reticulately perforated (occasional, irregular). Vessels without vestured pits. Primary medullary rays narrow (uniseriate). Wood diffuse porous; not storied; parenchyma absent.
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 unit 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.
Perianthwith 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. Corollavalvate (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 pistil2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary2 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, biochemistry. Alkaloids present. Iridoids not detected. Verbascosides not detected. Cornoside 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.). See comments under Loganiaceae.