Isolona perrieri
Tree up to 10-15 m high; d.b.h. to 20 cm; bark mottled light and dark grey with thin black lines; young branches drying black, glabrous; old branches grey, glabrous. Petioles 5-8 mm long, 1-1.2 mm in diameter, glabrous, leaf lamina inserted on side, faintly grooved adaxially. Leaf lamina 10-18 cm long, 3-4 cm wide, length:width ratio 3-4.2, narrowly elliptic, glabrous, green glossy, base narrowly cuneate to decurrent, apex acuminate, acumen 5-15 mm long; midrib glabrous on both sides; secondary veins 8-12 pairs, uniformally curving upwards, glabrous on both sides. Rhipidia 1-2, on leafy branches, sometimes on older leafless branches. Flowering pedicels (4-)10-15 mm long, ca. 0.5 mm in diameter, glabrous. Lower bracts 2-4, ca. 0.5 mm long, ca. 0.5 mm wide, glabrous. Upper bract absent. Sepals ca. 2 mm long, ca. 2 mm wide, length:width ratio ca. 1, very broadly ovate, glabrous, yellow, usually persistent in fruit; margins glabrous. Corolla green or light yellow when immature, bright yellow to purple red at anthesis; tube 2-6 mm long, 3-5 mm in diameter, lobe:tube ratio 2.5-5, glabrous; lobes (8-)11-20 mm long, 2-4 mm wide, length:width ratio 4-7, linear to very narrowly elliptic, coriaceous, spreading horizontally, sometimes curved and then spreading, glabrous. Receptacle ca. 4 mm in diameter. Stamens ca. 1.2 mm long; connective shield ca. 0.1 mm long, glabrous, those of innermost stamens extended or rarely slightly so over adjacent ovary wall. Ovary ca. 2 mm long, ca. 1.5 mm wide; stigma ca. 1.8 mm in diameter, glabrous, red at anthesis. Fruiting pedicels ca. 3.5 cm long, woody. Fruits 9-13 cm long, 5.5-7 cm in diameter, length:width ratio 1-1.5, globose to obconic, apex rounded to apiculate, apicule ca. 5-8 mm, striate, green, glabrous; pericarp ca. 5 mm thick. Seeds 22-25 mm long, 10-12 mm in diameter, ellipsoid, packed in white pulp; testa smooth, light brown; raphe not thickened, brown; hilum 7-8 mm long, 3-3.5 mm wide, elliptical.
Isolona perrieri is distinguishable by the narrowly elliptic leaves, very thin, long and glabrous flowering pedicels, as well as linear to narrowly elliptic corolla lobes, that spread horizontally. On dried material the corolla of some specimens is characteristically spread out into a star shape. It appears close to I. madagascariensis by the shape of the corolla lobes, but it is distinct by the length and thickness of the flowering pedicels. The specimens collected in the extreme south of the island present no clear morphological differences with the northern colections so they are retained within I. perrieri.
VU B2ab(iii). Isolona perrieri has a fair number of specimens in herbaria, and has been collected a few times these past two decades. It grows in numerous protected areas such as national parks (Andohahela), special reserves (Ankarana, Anjanaharibe Sud, Montagne d'Ambre, Nosy Mangabe) and strict nature reserves (Lokobe on the Nosy Be Island). However, the Area of Occupancy is smaller than 200 km2 and the species is found in less than 10 locations, thus the “vulnerable” category appears to be the best option.
Northern and southeastern Madagascar; in primary and secondary rain forest; at 200-1100 m altitude.