Inversodicraea digitata H.Hess

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 135

4. Inversodicraea digitata H.Hess

Inversodicraea digitata H. Hess (1953) 363, t. 8/3. — Ledermanniella digitata (H.Hess) Cusset (1974) 273; (1983) 372. — Type: Hess 50/239 (lectotype ZT n.v., isolectotype BM), Angola, Benguela,‘In einem Seitenfluss des Rio Catumbela, dem Rio Cubal da Hanha, zirka 50 km südlich Vila Mariano Machado [Ganda], auf zirka 1400 m Höhe gefunden. Der Cubal bildet dort Falle von etwa 2 m Höhe. Die Pflanze wurde erst am Ende der Trockenzeit gesammelt’, fl., fr., 29 Aug. 1950.

Etymology. Named for the shape of the leaflet lobes which resemble the fingers of a hand, with rounded tips.

Distribution — Angola.

Habitat & Ecology — Waterfalls with Hydrostachys polymorpha Klotzsch (Hess 50/232); 1000–1642 m altitude.

Conservation — Inversodicraea digitata is not listed on www. iucnredlist.org. Since three locations are known, and the area of occupancy can be calculated as 3 km 2, and since two of those two locations are in the Cuanza (Kwanza) drainage, we here assess the species as EN B2 ab(iii). Podostemaceae on the Cuanza are threatened (where they still exist) by the four hydroelectric dams which have changed the natural annual fluctuation of water levels. In 2014 (http://www.hydroworld. com/articles/2014/09/angola-plans-five-hydroelectric-projectson-middle-cuanza-river.html accessed 17 Feb. 2017) it was announced that five new, additional dams are to be constructed on the Cuanza.

Additional specimens. ANGOLA, Cuanza Sul, Mussende, R. Gango- Cuanza , 1000 m, fr., 13 June 1930, Gossweiler 9291 (BM, COI n.v., K, ZT n.v.) ; Bié Province, Cuquema River (Kwanza drainage), 13 km WSW of Kuito, S12°25'32" E16°49'6", 1642 m, fl., 19 May 2015, Goyder 8001 (K); ibid., st., 8 Feb. 2016, Goyder 8203 (K) .

Notes — Although Cusset (1983) stated that the holotypes of Hess’s 1953 names are at ZT, specimen locations are not given in the protologue, so lectotypification is needed. The ZT duplicate is therefore formally selected as lectotype since Hess is believed to have been based there.

Gossweiler 9291 (BM), previously cited by Cusset (1983) as I. cristata , is here recognised as a second record of I. digitata in view of the single stamen. This specimen was compared with the type of I. digitata at BM.

This species is similar to I. warmingiana and I. fluitans , also in Angola. It differs in that the leaflet lobes are finger-shaped: each is parallel-sided with round apices (not acute) according to the figure in Cusset (1983). The flowers have 1, not 2 stamens, and the stems are short, not more than 20 cm long. However, the leaflet lobes in the specimens seen are acute. Either the Cusset figure is misleading or the unseen type number at ZT differs from the remaining material in this respect.

The two Goyder specimens (8001 and 8203) represent the highest altitudinal record for the genus at 1642 m above sea-level. The first is in full flower but lacks leaves, while the second, from the identical spot but collected in the wet season while under water, has both fully developed and unfolding leaves but is sterile. Unusually in the genus, the ovaries dry red, and are reported as being red in life.