Family Gelsemiaceae

Gelsemiaceae (G. Don) L. Struwe and V.A. Albert

~ Loganiaceae sensu lato

Habit and leaf form. Erect or straggling shrubs (or undershrubs), or lianas. Self supporting, or climbing; the climbers stem twiners. Leaves opposite, or whorled; ‘herbaceous’; petiolate; connate to not connate; simple. Lamina entire; pinnately veined (?). Leaves stipulate to exstipulate (often reduced to an interpetiolar line). Stipules interpetiolar to intrapetiolar (sometimes reduced to a stipular sheath joining the opposite leaf bases); with colleters. Lamina margins obscurely sinuate dentate, or entire. Domatia occurring in the family (Coinochlamys (= Mostuea)); manifested as pockets.

Leaf anatomy. Extra-floral nectaries absent. Hairs present; eglandular. Complex hairs absent.

The mesophyll crystals without raphides.

Stem anatomy. Young stems cylindrical. Internal phloem present. Secondary thickening anomalous; from a single cambial ring. ‘Included’ phloem present. Xylem with fibre tracheids; without libriform fibres (the fibres septate or not). Vessel end-walls simple (mostly), or reticulately perforated, scalariform, and simple (but then mostly simple). Vessels with vestured pits (Mostuea), or without vestured pits (Gelsemium). Primary medullary rays very wide (Gelsemium), or narrow (Mostuea). Wood ring porous; not storied; parenchyma paratracheal (Gelsemium, or absent in Mostuea).

Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite; nearly always heterostylous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes and in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary (in one axil); with involucral bracts (two, basally united, in Coinochlamys), or without involucral bracts. Flowers bracteate (bracts variously shaped); one to many bracteolate; medium-sized to large (larger in Gelsemium); fragrant (at least in Gelsemium), or odourless (?); regular; 4 merous (occasionally, in Mostuea), or 5 merous (usually); tetracyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4 (ocasionally), or 5; 1 whorled; polysepalous (Gelsemium), or gamosepalous (Mostuea); blunt-lobed, or toothed. Calyx lobes when gamosepalous, markedly shorter than the tube to about the same length as the tube. Calyx regular; ‘mostly’ persistent; non-accrescent; imbricate; when K5, with the median member anterior. Corolla 4 (rarely, in Mostuea), or 5; 1 whorled; gamopetalous; imbricate; funnel-shaped (the tube much longer than the lobes); more or less regular; white, or yellow, or orange, or red, or blue (or lilac).

Androecium 4 (rarely, in Mostuea), or 5. Androecial members adnate (inserted at the middle of the corolla tube or below); all equal, or markedly unequal (short-styled Mostuea flowers); free of one another; 1 whorled. Stamens 4 (rarely), or 5; inserted near the base of the corolla tube, or midway down the corolla tube; isomerous with the perianth; oppositisepalous; alternating with the corolla members; filantherous, or with sessile anthers (? — the filaments very short). Filaments not appendiculate. Anthers separate from one another, or connivent; dorsifixed; dehiscing via longitudinal slits; latrorse; unappendaged. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; synovarious to synstylovarious (the style bifid, its branches bifid again); superior. Ovary 2 locular (glabrous or hairy). Gynoecium median. Ovary sessile. Gynoecium stylate. Styles 1–2; free to partially joined; apical. Stigmas 2, or 4 (each bifurcated); 4 lobed (twice dichotomously divided). Placentation axile (the placentas not bilobed). Ovules differentiated; 2 per locule (Mostuea), or 2–8 per locule (to ‘several’: Gelsemium); collateral (in 2–4 series); anatropous, or amphitropous (?); unitegmic. Outer integument contributing to the micropyle. Endothelium not differentiated. Hypostase absent.

Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal, loculicidal, and valvular. Fruit 1–6 seeded (to ‘several). Seeds endospermic (endosperm starchy or bony); conspicuously hairy, or not conspicuously hairy (but no hair tuft); flattened, winged (Gelsemium), or wingless. Cotyledons 2. Embryo straight, or curved. Testa smooth, or hairy.

Physiology, biochemistry. Alkaloids present. Iridoids detected; ‘Route I’ type (normal and seco, and complex indole alkaloids in both Mostuea and Gelsemium). Verbascosides not detected.

Peculiar feature. The funicles not as in Acanthaceae.

Geography, cytology. Holarctic, Paleotropical, and Neotropical. Eastern Asia, North and Central America, northern South America, Africa, Madagascar. 2n= 8, 16 (Gelsemium) and 20 (Mostuea. Supposed basic chromosome number of family: 4 and 10. Ploidy levels recorded: 2 and 4.

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.

Species 11. Genera 2; Gelsemium, Mostuea.

Leeuwenberg 1980, under Loganiaceae. Perhaps justifiably removed from Loganiaceae sensu lato by Struwe et al. (1994). They made no effort, however, to organize family descriptive data to the standards required for this package (see comment under Loganiaceae). On the basis of the much extended description given here, the family is nearer to Gentianaceae than to Rubiaceae and Apocynaceae. See comments under Loganiaceae.