Octolepis Oliv. sect. Octolepis

Rogers, Zachary S., 2005, A revision of Octolepis Oliv. (Thymelaeaceae, Octolepidoideae), Adansonia (3) 27 (1), pp. 89-111 : 93-94

Octolepis Oliv. sect. Octolepis

TYPE. — Octolepis casearia Oliv.

Monoecious shrubs, rarely small trees; bark usually lenticellate. Leaves alternate, persistent on mature stems, apex usually not aborting. Inflorescences lateral or sublateral, borne on the foliated portion of the stems; axes compact, racemose, elongating with up to c. 30 flowers per inflorescence. Flowers bisexual; sepals spreading or reflexed; petals 4 or 5, rarely 6; petal lobes broadly oblong, length/width ratio c. 1-1.5:1, erect, apex truncate or rounded; stamens 8 or 10. Fruits white, dry, dehiscence lines ± plane, not carinate on side of dehiscence lines; pericarp <2 mm thick, smooth when dry. Seeds with cotyledons c. 0.5(-1) mm thick [plants of continental Africa].

Octolepis Oliv. sect. Dioicae Z.S.Rogers , sect. nov.

TYPE. — Octolepis dioica Capuron.

Haec sectio a sectione Octolepide speciebus monoiciis

(nec diociis), habitu plerumque fruticoso (nec arborescente), foliis persistentibus (nec caducis), inflorescentiis lateralibus (nec terminalibus), petalis lobis late oblongis (nec triangularibus) et pericarpio tenui pagina laevi (nec crasso pagina plus minusve rugosa) differt.

Dioecious trees; bark rarely lenticellate. Leaves alternate to opposite, caducous on mature stems, apex often aborting. Inflorescences axillary, fasciculate; fascicles 1 to several-flowered, usually borne on defoliated portion of stems. Flowers unisexual; sepals spreading or erect; petals 4-6 (10); petal lobes narrowly triangular, length/width ratio c. 4-7:1, spreading, adpressed to sepals, apex acute, rounded at the tip. Staminate flowers with (8) 10 (12) (20) stamens; pistillode minute, obscured by many receptacle trichomes. Pistillate flowers with (8) 10 (12) (20) staminodes. Fruits green-yellow, fleshy, often bicostate on both sides of dehiscence lines; p e r i c a r p 2-8 mm thick, rugose or rugulose, often pitted, rarely smooth when dry. Seeds with cotyledons 1-1.5 mm thick [plants of Madagascar].

Key to the species of Octolepis

(Leaves of Malagasy species illustrated in Figure 2 )

1. Monoecious shrubs, rarely small trees; petal lobes broadly oblong (length/width ratio 1-1.5:1), apex truncate or rounded; fruits dry; [plants of Africa] ................................................................................ 2. O. casearia

1’. Dioecious trees; petal lobes narrowly triangular (length/width ratio 4-7:1), apex acute, rounded at the tip; fruits fleshy; [plants of Madagascar] .......................................................................................................... 2

2. Leaf blades chartaceous, apex attenuate-acuminate; secondary veins 15-25 pairs, closely-spaced; pedicels 0.3- 0.5 mm in diam.; receptacle trichomes surrounding the gynoecium 2.5-3.0 mm long in pistillate flowers .... ...................................................................................................................................... 1. O. aymoniniana

2’. Leaf blades coriaceous or coriaceous-chartaceous, apex usually slightly emarginate to retuse, sometimes acute, rounded, or obtuse, rarely short cuspidate; secondary veins rarely up to 12 pairs, sparsely-spaced; pedicels more than 0.5 mm in diam.; receptacle trichomes surrounding the gynoecium up to 2.5 mm long in pistillate flowers .................................................................................................................................... 3

3. Petioles 8-16 mm long; pedicels (in flower or fruit) 1.6-2.5 cm long, (1.5-) 2-3 mm in diam.; sepals 5-9 mm wide; bidif petals 10 (i.e. 20 lobes); stamens and staminodes 20 ...................................... 6. O. ratovosonii

3’. Petioles up to 8 mm long; pedicels (in flower or fruit) ≤ 1.5 cm long, up to 1 mm in diam.; sepals 2-4 mm wide; bifid petals 4-6 (i.e. 8-12 lobes); stamens and staminodes (8) 10 (12) .............................................. 4

4. Widest leaf blades 1-1.4 cm wide; pedicels less than 2 mm long; flowers 4-6 mm wide; largest fruits 1.6 cm long, dehiscence lines 1 or 2, rarely 3 .................................................................................. 4. O. ibityensis

4’. Widest leaf blades (1.6-) 2-4 cm wide; pedicels greater than 4 mm long; flowers more than 8 mm wide; largest fruits 2-3 cm long, dehiscence lines 4 or 5 .................................................................................... 5

5. Longest leaf blades 2.8-6.0(-6.5) cm long, c. 1-2.5 times longer than wide; leaf margin flat; flowers 8-11 mm wide ........................................................................................................................................ 3. O. dioica

5’. Longest leaf blades (7.0-) 7.4-12.4 cm long, c. 3-6 times longer than wide; leaf margin undulate; flowers 11- 13 mm wide .................................................................................................................. 5. O. oblanceolata

Figures

FIG. 2. — Leaf variation in the Malagasy species of Octolepis (abaxial leaf surface): A, B, O. dioica Capuron; C, D, O. oblanceolata (Capuron) Z.S.Rogers; E, O. ibityensis Z.S.Rogers; F, O. aymoniniana Z.S.Rogers; G, H, O. ratovosonii Z.S.Rogers. A, Rogers & Razakamalala 46; B, Service Forestier 6028; C, Réserves Naturelles 10459, type collection; D, Randriamampionona 1308; E, Randrianaivo et al. 8, type collection; F, Kotozafy & Randriamanantena 355, type collection; G, Rogers et al. 165, type collection; H, Ratovoson et al. 247, an exceptionally large leaf.