Inversodicraea Engl. ex R.E.Fr.

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 132

Inversodicraea Engl. ex R.E.Fr.

Rheophytic, hermaphroditic, annual and probably perennial herbs with narrowly ribbon-like, endogenously branching roots, gripping the substrate with adhesive root hairs (also known as rhizoids), distinct haptera (marginal disc-like holdfasts) rarely observed and not well-developed. Stems <1 cm to 80 cm long, branched or unbranched, erect and free-standing in absence of water, or horizontal, flowing in the current. Scale-leaves more or less spirally inserted, rarely in loose whorls, more or less covering the stems, dorsiventrally flattened, about as long as wide, appressed to stem or spreading, margin entire or variously toothed or lobed, rarely the scale-leaves long and awnlike ( I. mortonii ). Leaves deciduous (shed before flowering as plants are exposed by falling water levels), alternate, appearing 1– 5 times dichotomously branched, blade and petiole terete or dorsiventrally compressed, petiole not sheathing, stipules absent. Spathellae single, terminal, rarely appearing axillary, containing a single, inverted flower, rupturing before anthesis. Pedicel expanding to lift the flower from the spathellum. Tepals 2, usually filiform, inconspicuous at junction of androphore (or united staminal filaments) and gynophore. Stamens two (rarely three as monstrosities), with filaments more or less united at the base into the androphore, sometimes with a single stamen only, anthers tetrasporangiate, connective inconspicuous, pollen in dyads or monads, tricolpate. Ovary with short gynophore, unilocular with axile placentation (attached at base and apex only), ellipsoid to oblong-ellipsoid in side view, cylindrical or laterally compressed in the plane of the two sutures, becoming 6–8-ribbed longitudinally in fruit (the sutures with or without ribs), the ribs sometimes distally produced as wings. Ovules numerous, anatropous, completely covering the placenta. Styles 2 (3 in I. ntemensis and I. tchoutoi ), filiform with acute apex and minutely papillate, rarely triangular or slightly botuliform. Fruit dry, dehiscent by (1–)2 valves. Seeds numerous ellipsoid, released dry, epidermis mucilaginous and adhesive on wetting.

Distribution — Tropical Africa, Guinea-Bissau to Tanzania and South to Botswana, 30 species.

Note — Engler coined the name Inversodicraea and formally published it as a new name, giving himself as author ( Engler 1915). However, he appears to have been pre-empted in use of his name by Fries (1914) who while attributing it to Engler used the name first, to accommodate Dicraea tenax of Wright (1909). Thus Fries’ use of the name has priority over that of Engler according to the Code. The type species of Inversodicraea is thus I. tenax (C.H.Wright) R.E.Fr. , being the only species on which Fries (inadvertently) based the new genus.