Panicum dregeanum Nees, Fl. Afr. Austral. Ill.

Vorontsova, Maria S., 2018, Revision of the group previously known as Panicum L. (Poaceae: Panicoideae) in Madagascar, Candollea 73 (2), pp. 143-186 : 161

11. Panicum dregeanum Nees, Fl. Afr. Austral. Ill. 42. 1841.

Typus: SOUTH AFRICA. Prov. KwaZulu Natal: Port Natal, 100-400’ [30 – 120 m], s.d., Drège s.n. ( HAL [ HAL0063368 ] image seen, K [ K00025535 ]!, W [ W0000283 ] image seen) .

= Panicum ambongense A. Camus in Bull. Soc. Bot. France 99: 64. 1952. Lectotypus (designated here): MADAGASCAR. Prov. Antsiranana: Manongarivo, Ambongo , XII.1903, Perrier de la Bâthie 158 ( K [ K000805608 ]!), syn. nov.

Erect caespitose perennial, in dense compact tufts with a hardened woody base, 0.3 – 1 m tall, the stems glabrous. Leaf sheaths glabrous (although often pubescent in African populations). Ligule a ciliolate membrane. Leaf blades linear, flat or rolled, chartaceous, 10–20 × 0.2–0.4 cm, drying redgreen, glabrous (often pilose in African populations) on both sides. Panicles terminal, partly or fully exserted, 10– 25 cm long, oblong, a relatively small proportion of the plant, the branches shorter than the main axis of the panicle, appressed or ascending, scabrous. Spikelets ovate, apically acuminate, (1.8 –) 2 – 2.5 mm long, purplish, gaping open at maturity. Lower glume ½–3/4 as long as the spikelet, keeled, apically longacuminate to mucronate, 5-veined, finely scabrous on the keel. Upper glume as long as the spikelet, herbaceous, 5–7-veined, glabrous slightly keeled in the upper part. Lower floret male, with palea. Lower lemma herbaceous, 5-veined, glabrous. Upper lemma c. 1.5 mm long, shorter than the lower floret, smooth, shiny, brown.

Distribution and ecology. – Common across tropical Africa. Apparently less common in Madagascar occurring along the East coast and North-west coast, with two records from the High Plateau; coastal sand, open areas, and savanna, 0–1000 m ( Fig. 8A ). CAMUS (1952) reports that it forms thick lawns on damp sand near Manongarivo.

This species has not been seen in the field by the author but the distribution suggests it is likely to be an introduction.

Notes. – CAMUS (1952) reports that the spikelets open prior to anthesis. Lateral veins on the lower glume can be difficult to see but there are five visible on at least some spikelets and three are usually clear; these are important for identification. The clear perennial habit with a hard knotty root stock make an easy distinction from P. novemnerve and P. humile which have similarly long-acuminate glumes and lower lemma. CLAYTON (1982) keys out this species as “basal leaves silky-pubescent”, although some African and all the Malagasy populations have glabrous leaf sheaths.

The full typification of P. dregeanum is outside the scope of this work and will be published as part of an ongoing study of African Panicum s.l. The protologue of P. ambongense cites “Perrier de la Bâthie 11208 (168)” which is likely a transcription error as the only specimen found to match all the protologue data is numbered Perrier de la Bâthie 158, where the handwritten number “5” closely resembles a “6”. This specimen is chosen to be the lectotype because it is the only known original material of P. ambongense .

This species is illustrated in BOSSER (1969: Fig. 126e-h) and in CLAYTON (1989: tab. 7).

Additional material examined. – MADAGASCAR. Prov. Antananarivo: Ambohimanga , 27.III.1921, Decary 155 ( L [ K000805487 ], P [ P02222309 ]) ; vallée de la Saonjo , V.1964, Morat 1093 ( TAN) . Prov. Fianarantsoa: Nosy Varika , V.1953, Bosser 5571 ( TAN) ; Farafangana, III.1963, Bosser 17907 ( P [ P02608838 ]) ; PK 50 avant Mananjary , II.1964, Bosser 19023 ( P [ P03487904 ], TAN) ; Mananjary-Nosy Varika, I.1964, Bosser 19027 ( P [ P02608837 ], TAN) ; Mananjary, III.1909, Geay 7121 ( P [ P02608835 ]) ; Mananjary, III.1909, Geay 7143 ( P [ P02608828 ]) ; ibid. loco, III.1909, Geay 7151 ( P [ P02608830 ]) ; ibid. loco, III.1909, Geay 7351 ( P [ P02608829 ]) ; ibid. loco, III.1909, Geay 7673 ( P [ P02608834 ]) ; ibid. loco, III.1909, Geay 7762 ( P [ P02608827 ]) ; près de la baie du Namorona , 19.II.1964, Peltier & Peltier 4709 ( P [ P02726879 ]) ; 33 km S of Irondro, 26.III.1993, Turk & Beck 366 ( P [ P02325431 ], TAN) . Prov. Mahajanga: Besalampy, paturage de Beloke , IX.1958, Herb. Inst. Sci. Mada. s.n. ( P [ P02309334 ]) . Prov. Toamasina: Brickaville , I.1964, Morat 365 ( P [ P02608839 ]) . Sine loco: Geay 7242 ( P [ P02608832 ]) .

Figures

Fig. 8. – Distribution maps. A. Panicum cupressifolium A. Camus (stars), P. danguyi A. Camus (triangles), P. dregeanum Nees (circles) and P. flacourtii A. Camus (squares); B. Panicum humbertii A. Camus (stars), P. humile Nees ex Steud. (triangles), P. ibitense A. Camus (circles) and P. inconspicuum Voronts. (squares).