Panicum subhystrix A. Camus

26. Panicum subhystrix A. Camus in Bull. Soc. Bot. France 72: 708. 1925 (Fig. 13C, 17).

Lectotypus (designated here): MADAGASCAR. Prov. Fianarantsoa: Andringitra massif, II.1922, Perrier de la Bâthie 14545 (TAN [TAN000388]!; isolectotype: B [B 10 0168672] image seen, K [K000805589]!, P [P00224774, P00224776]!).

= Isachne perrieri A. Camus in Bull. Soc. Bot. France 72: 306. 1925. ≡ Panicum betafoense A. Camus in Mém. Inst. Sci. Madagascar, Sér. B, Biol. Vég. 1: 111. 1949. Lectotypus (designated here): MADAGASCAR. Prov. Antananarivo: W de Betafo, V.1920, Perrier de la Bâthie 13183 (P [P00450277]!; isolectotype: P [P02241484]!), syn. nov.

= Isachne hirtissima A. Camus in Bull. Soc. Bot. France 73: 916. 1927. ≡ Panicum betafoense subsp. midongyense A. Camus in Bull. Soc. Bot. France 107: 210. 1960. Lectotypus (designated here): MADAGASCAR. Prov. Fianarantsoa: env. de Midongy, III.1919, Perrier de la Bâthie 12523 (P [P00450255]!; isolectotype: K [K000244643]!, P [P00450254, unmounted]!), syn. nov.

Annual or perennial, creeping or ascending, stems often branched at the base to form a dense mat, to 1 m long, the culms glabrous to pilose with bulbous-based cilia. Leaf sheaths glabrous to pilose with bulbous-based cilia. Ligule a glabrous or ciliolate membrane. Leaf blades lanceolate to filiform, flat or rolled, chartaceous, amplexicaul when broad, 3–7 × 0.1–1 cm, drying yellow-green, glabrous to pubescent on both sides. Panicles terminal, fully exserted, 3–10 cm long, elliptic, the branches lax, ascending, with glandular patches, glabrous or pubescent, the pedicels filiform and flexuous. Spikelets broadly ovate, asymmetric, apically obtuse, 1.5–2 mm long, yellowish or purple, gaping open at maturity. Lower glume equalling or slightly exceeding the spikelet, membranous, acute, 1–3-veined, glabrous to pubescent, separated from the rest of the spikelet by a short internode. Upper glume as long as the spikelet, herbaceous, 5-veined, hirsute with bulbous-based trichomes at maturity. Lower floret male, with palea. Lower lemma thinly cartlaginous, 5–7-veined, sometimes hooded, glabrous. Upper lemma shorter than the lower floret, the whole surface with a dense covering of fine verruccae, often dehiscing before the lower floret.

Distribution and ecology. – Endemic to the Central Plateau high elevation grassland, woodland, tapia forest, in damp areas and frequently sheltered by rocks, common on gneiss and quartzite, 1200–2300 m (Fig. 16A).

Notes. – This species is extraordinarily variable in its vegetative growth pattern, with leaves from filiform rolled to lanceolate 1 cm wide. This variability is often seen within a single population, while the spikelet morphology is constant. The scandent habit and long lower glume of Panicum subhystrix can be similar to the sympatric P. perrieri which has longer spikelets and the lower glume not offset from the rest of the spikelet. Panicum subhystrix is often seen in the vegetative state with a distinct juvenile morphology which is difficult to recognise.

The lectotype of P. subhystrix is chosen for its good quality material, and to improve the availability of type material in Madagascar; the B duplicate is not annotated with a collector number but the note by the species author implies this is a fragment of Perrier de la Bâthie 14545. The lectotype of Isachne perrieri is chosen for its best quality material. The lectotype of I. hirtissima is chosen because it is the only duplicate at the species author’s place of work annotated by the author.

Panicum betafoense was published as a replacement name for Isachne perrieri since Panicum perrieri was already a name in use for another species since 1925. Panicum betafoense was published by means of an indirect reference (TURLAND et al. 2018: Art. 41.3).

Additional material examined. – MADAGASCAR. Prov. Antananarivo: Analandraisoa, IV.1963, Bosser 17614 (P [P02307346]); env. Ibity, 6.V.1970, Bosser 20259 (P [P06795929]); ibid. loco, 6.V.1970, Bosser 20261 (P [P06795932]); Ibity massif, V.1969, Morat 3185 (P [P02307393]); ibid. loco, II.1914, Perrier de la Bâthie 10269 (P [P02251485]); Andranomongitsy près Banomointy, VI.1912, Perrier de la Bâthie 10290 (P [P02251496]); Betafo, VI.1912, Perrier de la Bâthie 10296 (P [P06768765]); Mt Ibity, Perrier de la Bâthie 10769 (P [P02251489, P02251507]); Andranomongitsy près Banomointy, VI.1912, Perrier de la Bâthie 10790 (P [P02251488]); Betafo, VI.1912, Perrier de la Bâthie 10796 (P [P06768764]); NW de Betafo, V.1962, Bosser 16375 (P [P06795931]); 2–3 km E of Ibity cement factory, Beampombo, 20°04'14"S 47°00'11"E, 28.IV.2004, Rogers et al. 346 (P [P02373632]). Prov. Fianarantsoa: Itremo, IX.1956, Bosser 9838 (P [P06795930]); Fianarantsoa, IV.1964, Bosser 19534 (P [P02324486], TAN); Ambatofinandrahana, IV.1964, Bosser 19556 (P [P02251487], TAN); Itremo, IV.1964, Bosser 19564 (P [P02251486]); Itremo, Ambatomenaloha, IV.1964, Bosser 19663 (P [P02324485], TAN); Ambalavao, 20.X.1940, Decary 15914 (P [P06795968]); Itremo, X.1954, Morat 752 (P [P02307321]); Ambalavao, IV.1972, Morat 3919 (P [P02325447], TAN); à l’W d’Itremo, 17.I.1955, Humbert 30070 (P [P02251502, P0225150]); ibid.loco, 17.I.1955, Humbert 30079 (P [P02251504]); ibid. loco, 17.I.1955, Humbert 30081 (P [P02251505]); ibid. loco, 17.I.1955, Humbert 30082 (P [P02251497]); ibid. loco, 17.I.1955, Humbert 30083 (P [P02251503]); ibid. loco, 17.I.1955, Humbert 30084 (P [P02251501]); Itremo, Ianasana, 20°34'39"S 46°34'54"E, 15.III.2013, Nanjarisoa & Andriamampionona 14 (K, TAN); Itremo, Andohatanimena, 20°31'15"S 46°33'59"E, 19.II.2014, Nanjarisoa et al. 145 (K, TAN); Itremo, Soatsihotapaka, 20°31'35"S 46°34'52"E, 20.II.2014, Nanjarisoa et al. 152 (K, TAN); ibid. loco, 20.II.2014, Nanjarisoa et al. 154 (K, TAN); Itremo, Ankevo, 20°39'36"S 46°34'46"E, 13.III.2012, Ratovonirina et al. 185 (K, TAN [K000753875]); Itremo, Ianasana, 20°34'41"S 46°35'05"E, 13.III.2012, Ratovonirina et al. 189b (K, TAN); Itremo, Ambatoantrano, 20°33'51"S 46°34'48"E, 14.III.2012, Vorontsova et al. 748 (K, TAN); Itremo, Soatsihotapaka, 20°30'44"S 46°34'43"E, 26.II.2013, Vorontsova et al. 1022 (K, TAN); Itremo, Ianasana, 20°34'46"S 46°35'18"E, 20.V.2014, Vorontsova 1586 (TAN); ibid. loco, 20.V.2014, Vorontsova & Nanjarisoa 1597 (TAN). Prov. Toamasina: Maningory, chutes de Ambato, 14.XII.1944, Homolle 1833 (P [P02251500]).