4. Panicum ankarense A. Camus in Bull. Soc. Bot. France 92: 50. 1945 (Fig. 4).

Lectotypus (designated here): MADAGASCAR. Prov. Antsiranana: Ankarana, entre Ambondromifehy et Ambilomagodra, 250 m, XI.1937 – I.1938, Humbert 18989 (P [P02251329]!; isolectotype: BR!, E!, EA!, G [G00022461] image seen, K!, L!, MAU!, MO!, P [P02251330, P02251331]!, PRE!, S!, SI!, TAN!, US!) . Syntypus: MADAGASCAR. Prov. Antsiranana: NW de la falaise de l’Ankarana, s.d., Humbert 18855 (not found) .

Erect caespitose perennial, 50–80 cm tall, the culms glabrous, the nodes pubescent. Leaf sheaths glabrous to moderately pubescent at the top. Ligule a ciliolate membrane. Leaf blades linear, flat, chartaceous, 15– 25 × 0.6– 1.5 cm, drying greenbrown, cross veins visible when dry, glabrous to moderately pubescent on both sides. Panicles terminal, fully exserted on a peduncle 3– 10 cm long, 15– 20 cm long, diffuse, with c. 20– 40 spikelets per panicle, the branches wiry, flexuous, scaberulous, sometimes with gland-tipped cilia, the pedicels 3–12 mm long. Spikelets oblong, apically obtuse, 2.8–4 mm long, drying whitish, partly open at maturity. Lower glume ½ – 2/3 as long as the spikelet, chartaceous, apically acute, 5–7-veined, glabrous, separated from the rest of the spikelet by an internode c. 0.5 mm long. Upper glume as long as the spikelet or a little shorter, herbaceous, 7-veined, glabrous. Lower floret male, with a fully developed palea. Lower lemma herbaceous, 5-veined, glabrous. Upper lemma, smooth, shiny, pale, with a small apical crest.

Distribution and ecology. – Narrow endemic restricted to dry forest on limestone in northern Madagascar, 150–250 m (Fig. 2A).

Notes. – Rare species known from five collections only. Appearance of the plant, the long wiry inflorescence branches, and the obtuse oblong spikelets are generally similar to P. trichocladum but the spikelets are larger and the lower glume has 5–7 veins.

The second syntype collection Humbert 18855 was not found; the only known duplicate of Humbert 18855 is a type of P. bicuspidatum A. Camus (= P. subalbidum Kunth) from the same locality.

The lectotype sheet was selected due to its best quality reproductive material.

Additional material examined. – MADAGASCAR. Prov. Antsiranana: Orangéa, 22.I.1960, Humbert & Cours 32300 (K [K000805592]) ; Daraina, forêt d’Ampondrabe, 12°58'16"S 49°42'02"E, 15.II.2005, Nusbaumer & Ranirison 1471 (G [G00019258]) ; Daraina, forêt de SolaniampilanaMaroadabo, 13°05'20"S 49°34'43"E, 8.II.2006, Nusbaumer & Ranirison 2272 (G [G00074508]) ; Ampandriantsira, W of Irodo village, 12°39'27"S 49°31'43"E, 8.II.2015, Rakotonasolo et al. 2577 (K [K001036478], TAN) ; Daraina, Bekaraoka, 13°06'06"S 49°42'40"E, 15.II.2004, Ranirison & Nusbaumer 449 (G [G00006817], P [P02726821]) .