Diplazium humbertii (C.Chr.) Pichi Sermolli (1973: 444) (Figs. 4 E–F, 6–7).

Athyrium humbertii Christensen (1937: 54)

Lectotype (designated by Pichi Sermolli 1973):— D.R. CONGO. North Kivu: Montagnes à l’Ouest du Lac Kivu (Congo Belge). Forêt, 2000–2400 m, February–March 1929, H. Humbert 7497 (BM000918405!; isolectotype BM000918404!)

Specimens seen: — RWANDA. Western Province: Nyungwe National Park, route Astrida (= Huye) – Bukavu, vers km 93, forêt de Rugege (= Nyungwe) près d’Uwinka, Territ. Shangugu (= Rusizi), 24 September 1956, G. Troupin 2598 (BR0000013688578); a sud-est del lago Kivu a 45 km da Bukavu lungo la strada per Astrida (= Huye), 15 August 1956, R. Pichi Sermolli 5323 (BR0000013688585); Forêt de Nyungwe, environs de Kamiranzovu, Préfecture Cyangugu (= Rusizi), September 1971, G. Bouxin 1211 (BR0000013688462); Kamiranzovu, 11 August 2007, E. Fischer s.n. (KOBL); Cyamudongo Forest, 4 April 2021, E. Fischer s.n. (KOBL).

Distribution in Rwanda: —Western Province, Nyungwe National Park.

Distribution in Africa: Eastern D.R. Congo, Western Uganda, Western Rwanda, Western Burundi, Western Tanzania. Albertine Rift endemic.

Habitat: —Montane rainforest, elev. 1900–2400 m.

Note: —The spores (Fig. 4 E, F) resemble those of Diplazium cyamudongoense sp. nov. (Fig, 4 A–D) and have a cristate perispore, 54.3–57.2 × 28.6–37.1 µm, the alae are 5.7–7.15 µm high and 1.5–2.86 µm wide. The remaining perispore bears up to 1.4–1.6 µm long spine-like scattered projections.