Panicum vohitrense A. Camus

Vorontsova, Maria S., 2018, Revision of the group previously known as Panicum L. (Poaceae: Panicoideae) in Madagascar, Candollea 73 (2), pp. 143-186 : 181-182

29. Panicum vohitrense A. Camus in Bull. Soc. Bot. France 92: 51. 1945 ( Fig. 13D ).

Lectotypus (designated here): MADAGASCAR. Prov. Toamasina: sur le Vohitra , 300 m, IX.1921, Perrier de la Bâthie 14014 ( P [ P00450243 ]!; isolectotype: [ P00450241 , P00450242 ]!) .

Annual or short lived perennial, rooting at lower nodes; prostrate, to 1 m long, the culms glabrous. Leaf sheaths glabrous or with ciliate edges. Ligule a lacerate ciliolate membrane. Leaf blades lanceolate, flat, membranous, 1.5–5 × 0.3–1.1 cm, drying glaucous to yellow-green, cross veins visible when dry, glabrous on both sides, with a few cilia around the ligule and on sheath margins. Panicles terminal and axillary, partly or fully exserted on a peduncle to 5 cm long, 4–13 cm long, diffuse, the branching distichous or in threes, the branches divergent at maturity, glabrous, the spikelets not clustered at the tips of branches, the pedicels 2.5–8 mm long. Spikelets ovate-elliptic, apically rounded to acute, 1.3–1.7 mm long, yellowish, never gaping open. Lower glume up to 1/3 as long as the spikelet, obtuse to acute, 0–1-veined, glabrous. Upper glume as long as the spikelet, membranous, 3-veined, glabrous or with a few small trichomes. Lower floret barren, without a significant palea. Lower lemma membranous, 3–5-veined, glabrous or with minute trichomes. Upper lemma smooth, shiny, pale.

Distribution and ecology. – Endemic to the east coast and northern wet forests of Madagascar. Humid forest understory, often by the sides of a stream, often on laterite or gneiss, 450–1800 m ( Fig. 16B ).

Notes. – This species is distinguished from P. mitopus by its single long pedicels, divergent from the rest of the synflorescence branches. It is unclear whether this character is genetic in origin or a reflection of humid environment so it is possible this species may prove to be conspecific with P. mitopus .

The lectotype sheet is selected for its best quality material annotated by the species author.

Additional material examined. – MADAGASCAR. Prov. Antsiranana: massif du Marojejy , 9.XI.1959, Humbert & Saboureau 140 ( P [ P03182743 ]) ; ibid. loco, 28.XI.1948, Humbert & Capuron 22135 ( P [ P02608141 ]) ; entre la Haute Andramonta et la Majaika , 3.I.1951, Humbert & Capuron 24843 ( P [ P02608144 ]) ; Reserve Speciale Manongarivo , Bekolosy , 14°02'50"S 48°17 '46"E, 12.V.2014, Vorontsova & Onjalalaina 1466 ( K, P, TAN) . Prov. Fianarantsoa: Andringitra , IV.1964, Bosser 19484 ( P [ P02309317 ]) ; Pic Ivohibe , 21.IX.1926, Decary 5410 ( P [ P01973817 ]) ; Ikongo , 17.X.1926, Decary 5756 ( P [ P01973835 ]) . Prov. Toamasina: mont Ankaroka , Humbert & Cours 17532 ( P [ P01973797 ]) ; massif de l’Andrangovalo X.1937, Humbert & Cours 17883 ( P [ P01973796 ]) ; NE of Ambanizana , 15°38'00"S 49°58'E, 20.X.1986, Lowry et al. 4210 ( P [ P02661726 ]) .

Figures

Fig. 13. – A. Habitat of Panicum spergulifolium A. Camus with P. spergulifolium pink at the forefront; B. Habitat of P. voeltzkowii Mez with the green-brown mat of P. voeltzkowii across the forefront; C. Panicum subhystrix A. Camus; D. Panicum vohitrense A. Camus. [A: Vorontsova et al. 1218; B: Vorontsova et al. 1391; C: Ratovonirina et al. 185; D: Vorontsova & Onjalalaina 1466] [Photos: M.S. Vorontsova]

Fig. 16. – Distribution maps. A. Panicum subalbidum Kunth (stars), P. subhystrix A. Camus (triangles), P. trichocladum K. Schum. (circles) and P. voeltzkowii Mez (squares); B. Panicum vohitrense A. Camus (stars), Trichanthecium brazzavillense (Franch.) Zuloaga & Morrone (triangles), T. parvifolium (Lam.) Zuloaga & Morrone (circles) and Urochloa maxima (Jacq.) R.D. Webster (squares).