Rhodolaena

Schatz, George E., Lowry Ii, Porter P. & Wolf, Anne-Elizabeth, 2000, Endemic families of Madagascar. VI. A synoptic revision of Rhodolaena (Sarcolaenaceae), Adansonia (3) 22 (2), pp. 239-252 : 241

Key to the species of Rhodolaena

1. Young branches and midrib of blade below usually with dense golden indument, the trichomes ca. 0.5 mm long; stipules linear to narrowly triangular, persistent .......................................................... 5. R. humblotii

1’. Young branches and midrib of blade below glabrous, or twigs with dense brownish indument, the trichomes less than 0.1 mm long; stipules triangular, caducous .................................................................................. 2

2. Leaves with a rounded apex (rarely acute) and usually emarginate, sometimes also with a tiny mucro ........ 3

2’. Leaves with an acute to acuminate apex .................................................................................................... 4

3. Twigs usually glabrescent, and often glaucescent; leaves strongly coriaceous, the largest blade usually greater than 7 cm long (rarely less); inner sepals coriaceous, (2-) 2.5-3.5 cm long .............................. 4. R. coriacea

3’. Twigs with dense brownish indument; leaves chartaceous, the largest blade usually less than 6 cm long (rarely to 7 cm); inner sepals chartaceous, not exceeding 1.8 cm long ............................................ 3. R. bakeriana

4. Leaves with secondary veins nearly perpendicular to the midvein (> 80°); involucre a distinct collar at anthesis; ovary densely golden tomentose; seeds with dense white indument ........................................ 6. R. leroyana

4’. Leaves with secondary veins ascending (<70°); involucre mostly indistinct at anthesis; ovary subglabrous, or white puberulent to tomentose; seeds glabrous .......................................................................................... 5

5. Leaves drying olive green, with evident secondary veins on the glossy upper surface strongly ascending (<45° to the midvein), tertiary veins forming an open reticulated network; twigs lacking conspicuous raised lenticels; flowers solitary; fruit large, the valves 2-3.3 × 2-2.5 cm ...................................... 7. R. macrocarpa

5’. Leaves drying maroon-brownish, the secondary veins usually obscure on the dull upper surface, ascending at a 60-70° angle to the midvein, tertiary veins forming a dense reticulated network; twigs often with distinctly raised rusty brown lenticels; flowers paired ................................................................................................ 6