Octolepis casearia Oliv.

Rogers, Zachary S., 2005, A revision of Octolepis Oliv. (Thymelaeaceae, Octolepidoideae), Adansonia (3) 27 (1), pp. 89-111 : 97-98

2. Octolepis casearia Oliv.

J. Linn. Soc. Bot. 8: 161, t. 12. (1865). — Type: Mann 2306, Nigeria, State Cross River, River Old Calabar , [4°54’N, 8°16’E], Feb. 1863, fl. (lecto-, K!, designated by AYMONIN 1966a) .

Shrubs 2-3 m tall, rarely small trees to 7 m tall; bark usually lenticellate; stems with internodes 0.9-6.1 cm long; young stems densely to sparsely strigose-tomentose. Leaves alternate, blades b ro a d l y o b ova t e o r e l l i p t i c, c. 5-3 1 × 3.5- 10.5 cm, length/width ratio c. 2.5-4:1, coriaceous or rarely subcoriaceous, sometimes bullate, surfaces usually discolorous, adaxial surface glabrous, abaxial surface usually lighter green, glabrescent or sparsely strigose, trichomes c. 0.3- 0.5 mm long, apex acuminate or acute, acumen up to 2.2 cm long, margin revolute, glabrescent or sparsely strigose, base cuneate or short attenuate; midrib strongly raised on abaxial surface, sparsely to moderately strigose; venation strongly raised on both surfaces, secondary veins c. 6- 13 pairs, usually strongly arched toward apex, angle of divergence from midrib 55-75°, submarginal loop c. 4-11 mm from margin; petioles c. 4-10 mm long, strigose-tomentose. Inflorescences lateral or sublateral, borne on foliated portion of the stem; axes to 6.7 mm long, c. 2 mm wide, with up to c. 30 flowers per inflorescence, densely strigose-tomentose; pedicels c. 3-8 mm long, strigose-tomentose. Flowers 6-11 mm wide; sepals 4 or 5, rarely 6, ovate or subtriangular, 2.5- 6 × 1.3-3.1 mm, reflexed or spreading, coriaceous to subcoriaceous, strigose-tomentose on both surfaces, margins tomentose, apex acute; petals 4 or 5, rarely 6, erect, glabrescent or tomentose-strigose on both surfaces; each petal lobe broadly oblong, 1.1-3 × 0.5-1.4 mm, length/width ratio c. 1- 1.5:1, coriaceous to subcoriaceous, apex truncate or rounded, densely tomentose, margin usually densely tomentose; stamens 8 or 10, rarely 12; filaments 1.4-5.5 × 0.2-0.3 mm, strigose-tomentose or glabrescent; anthers 0.7-1 × 0.3-0.5 mm; ovary subspheroidal, 0.9-1.5 × 0.8-1.3 mm, densely strigose-hirsute, surrounded by many erect receptacle trichomes, each c. 0.5 mm long; style 1.1-1.6 × 0.3-0.5 mm, strigose. Fruits white, ovoid-suborbicular, 1-1.5 × 1-1.3 cm; dehiscence lines 2-5 (i.e. 2-5 carpels develop), plane or slightly raised; pericarp dry, 1-2 mm thick, smooth, glabrescent or sparsely strigose, or covered with dense persistent indument. Seeds dark brown or black, 8-13 × 5-8 mm, puberulent, indument denser near poles and on adaxial surface, trichomes c. 0.2-0.5 mm long, erect or adpressed.

T Y PI F I C AT I O N. — In the protologue of Octolepis casearia ( OLIVER 1865) , three collections were cited (Mann s. n., Sept. 1862; Mann s. n., Feb. 1863; and Thomson s. n.). No specimens collected by THOMSON have been located, but two numbered specimens collected by MANN are deposited in the Kew herbarium, which correspond to the dates cited in the protologue (Mann s. n., Sept. 1862 [= Mann 1815] and Mann s. n., Feb. 1863 [= Mann 2306]). These collections undoubtedly represent the two specimens mentioned by OLIVER (1865). In the Thymelaeaceae treatments appearing in the Flore du Gabon ( AYMONIN 1966a: 46) and Flore du Cameroun ( AYMONIN 1966b: 80), only one of these syntypes (Mann 2306) was mentioned as the type of O. casearia , thereby effectively lectotypifying the name according to Article 7.11 of the Code ( GREUTER et al. 2000).

Octolepis casearia is easily recognized from all other members of the genus by its bisexual flowers, broadly oblong petal lobes with truncate or rounded apices, dry fruit with a thin pericarp, and its central and west African distribution.

Octolepis casearia is circumscribed here to include all previously described continental African taxa. Earlier authors have also recognized a broadly circumscribed O. casearia , due to the overlapping, continuous morphological variation within characters used to distinguish the species. Here, O. decalepis Gilg , previously segregated by some because of its (almost) always 5-merous flowers, is also included within O. casearia .

Flower meristicity is rather variable geographically within Octolepis casearia and inconsistent among specimens, sometimes even for collections made from the same locality or even those taken from the single plant (meristicity is much more variable within the Malagasy species). Octolepis casearia has 5-merous flowers in Ivory Coast and almost always in Liberia, 4-merous flowers in Nigeria, 4- or 5-merous flowers in Cameroon and Gabon, and 5-merous flowers in the Republic of the Congo (Brazzaville).

In contrast, variation in fruit morphology clearly delimits two distinct groups of specimens of Octolepis casearia . One group with densely pubescent fruits, includes the type of O. flamignii De Wild. , and occurs in the Democratic Republic of the Congo (Kinshasa), southeastern Gabon, and the Republic of the Congo (Brazzaville), while a second group with glabrescent or sparsely strigose fruits, corresponds to O. casearia var. casearia , and grows in Cameroon, Ivory Coast, Gabon, Liberia, Nigeria, and the Republic of the Congo (Brazzaville). These two groups are slightly allopatric, but some populations come within c. 60 km of each other in Gabon and the Democratic Republic of the Congo ( Fig. 4 ). These two distinct groups are recognized as varieties of O. casearia .

Figures

FIG. 4. — Distribution map of Octolepis casearia Oliv. var. casearia (▲) and O. c. var. flamignii (De Wild.) Z.S.Rogers (●). Outlines correspond to country boundaries in central and western Africa.