Pentachlaena, H. Perrier

Lowry Ii, Porter P., Haevermans, Thomas, Labat, Jean-Noël, Schatz, George E., Leroy, Jean-François & Wolf, Anne-Elizabeth, 2000, Endemic families of Madagascar. V. A synoptic revision of Eremolaena, Pentachlaena and Perrierodendron (Sarcolaenaceae), Adansonia (3) 22 (1), pp. 11-31 : 16

PENTACHLAENA H. Perrier

Bull. Mus. Natl. Hist. Nat. 26: 669 (1920).

TYPE. — Pentachlaena latifolia H. Perrier.

The genus Pentachlaena was originally described with a single species ( P. latifolia ), which is restricted to the Col des Tapias, the Ibity massif, and the area immediately to the south. CAPURON (1970) mentioned a second member of the genus growing at low elevations in the east, which he later described ( CAPURON 1973) as P. orientalis . Here we describe a third species, known only from the type collection in flower, made at Betampona RNI over 40 years ago, but which could very well still occur in the wild, considering how many other rare species characteristic of low elevation humid evergreen forest have been rediscovered there within the last several years. Pentachlaena can be distinguished from its presumed relatives by its dehiscent, 5-locular fruit with a particularly thick, almost woody exocarp, in which each locule contains 4-6 seeds.

Key to the species of Pentachlaena

1. Inflorescences terminal, branched, with ca. 10 flowers; leaves obovate, with 5-6 pairs of secondary veins, apex distinctly emarginate; Betampona RNI .............................................................. 1. P. betamponensis

1’. Inflorescences axillary and occasionally terminal, with 2 flowers; leaves elliptic to orbicular, with (7-)8-12 pairs of secondary veins, apex rounded to truncate, rarely somewhat emarginate ...................................... 2

2. Leaves elliptic, strongly discolorous, largest blade 9.5-18 × 7-12 cm; peduncles at least 15 mm long; bracts subtending flowers 10-15 mm long, deeply laciniate; seeds pubescent; sublittoral forest on sand overlaying laterite, Tampolo STF, Analalava, Betampona RNI ............................................................ 2. P. orientalis

2’. Leaves broadly elliptic to orbicular, weakly discolorous, largest blade 5-9 × (3.5-) 4-7 cm; peduncles less than 8 mm long or flowers subsessile; bracts subtending flowers to 5-7 mm long, entire or slightly dentate; seeds glabrous; Tapia woodland on outcrops of quartzite and perhaps other substrates, Col des Tapias, Ibity and area immediately S .......................................................................................................... 3. P. latifolia

Clé des espèces de Pentachlaena

1. Inflorescences terminales, ramifiées, à 10 fleurs environ; feuilles obovées, à 5-6 paires de nervures secondaires, apex nettement émarginé; Betampona RNI ................................................................ 1. P. betamponensis

1’. Inflorescences axillaires et parfois terminales, à 2 fleurs; feuilles elliptiques à orbiculaires, à (7-)8-12 paires de nervures secondaires, apex arrondi à tronqué, rarement légèrement émarginé .............................................. 2

2. Feuilles elliptiques, fortement discolores, limbes les plus grands 9.5-18 × 7-12 cm; pédoncules mesurant au moins 15 cm de long; bractées florales de 10-15 mm de long, profondément laciniées; graines pubescentes; forêt sublittorale sur sable superposé sur latérite, Tampolo STF, Analalava, Betampona RNI.... 2. P. orientalis

2’. Feuilles largement elliptiques à orbiculaires, faiblement discolores, limbes les plus grands 5-9 × (3.5-) 4-7 cm; pédoncule mesurant moins de 8 mm de long ou fleurs subsessiles; bractées florales mesurant jusqu’à 5- 7 mm de long, entières ou légèrement dentées; graines glabres; bois de Tapia sur rochers de quartzites et peutêtre d’autres substrats, Col des Tapias, Ibity et environs immédiatement au S ............................ 3. P. latifolia