Sabicea floribunda, K. Schum.

Lachenaud, Olivier, Zemagho, Lise & Sonké, Bonaventure, 2020, A synopsis of the Sabicea floribunda group (Rubiaceae) from Central Africa, including three new species, Candollea 75 (1), pp. 115-143 : 118-121

Key to the species of the Sabicea floribunda group

1. Leaves strongly discolorous, the lower side covered with dense buff woolly hairs (these occasionally sparser in older leaves) .......................................................................... 2

1a. Leaves green on both sides, the indumentum not woolly ..................................................................................... 3

2. Stems, petioles and lower leaf surface with uniform woolly indumentum; inflorescence capitate or rarely developing short ramifications in fruiting stage; fruits white; seed surface with close parallel striations (SE Cameroon to Cabinda) ...................................................... 4. S. nobilis

2a. Stems, petioles and lower leaf surface with both woolly hairs and long straight hairs (the latter not present between the veins); inflorescence with ramifications already distinct at flowering stage; fruits purplish-red when young, blackish when mature, seed surface reticulate (S Cameroon, Central Gabon, SW Republic of Congo) ............. 1. S. couteronii

3. Leaves hirsute on both sides and conspicuously bullate in life (not so when dry); stipules and stems also hirsute ... 4

3a. Leaves glabrescent or with very sparse hairs above (except sometimes on veins), never bullate; stipules glabrescent or with appressed hairs; stems mostly with appressed hairs (sometimes hirsute in S. floribunda and S. segregata ) .... 5

4. Bracts and calyces dark red (W Gabon: mostly WongaWongué Reserve) .... 7a. S. sanguinosa subsp. sanguinosa

4a. Bracts and calyces pale green (W Gabon: Ogooué delta) ....................................... 7b. S. sanguinosa subsp. viridis

5. Calyx lobes bicoloured (when fresh) with pinkish-red base and green apex; inflorescence subsessile (peduncle <3 mm) and glomerulate at anthesis, becoming cymose in fruit; stipules auriculate at base; fruit pure white, without granules in mesocarp; seed surface coarsely reticulate (NW and Central Gabon) .................. 2. S. dichrosepala

5a. Calyx lobes not as above; inflorescence with peduncle> 3 mm and ramifications usually apparent at anthesis; stipules not auriculate; fruit variable in colour, with darker granules in mesocarp; seeds usually with close parallel striations (coarsely reticulate in S. proselyta ) ................ 6

6. Corolla lobes white or greenish at anthesis; leaves with tertiary veins markedly raised below and much stronger than quaternary veins; fruits ellipsoid, white or pale grey; inflorescences 1.2–7.5 cm long; stipules densely pubescent, at least in central part .................................................. 7

6a. Corolla lobes brown at anthesis; leaves with tertiary veins not or hardly raised below, not or hardly more apparent than quaternary veins; fruits globose, or if ellipsoid maturing red or black; inflorescences 3–37 cm long; stipules glabrescent (apart from the margins) to densely pubescent .............. 8

7. Calyx lobes dark red, villose outside and puberulous inside; seed surface with close parallel striations; indumentum of lower leaf surface erect, consisting of a mixture of short whitish and longer rufous hairs; calyx tube glabrous inside (SW Gabon) ..................... 6. S. rubiginosa

7a. Calyx lobes green or brownish green, puberulous on both sides; seed surface coarsely reticulate; indumentum of lower leaf surface usually appressed (sometimes erect except on veins) and uniformly whitish; calyx tube villose inside (S Cameroon to SW Republic of Congo) ...... 5. S. proselyta

8. Calyx lobes shortly elliptic, 0.8–3 × 0.4–2 mm, rounded and often spotted dark green at apex, 1.4–2(–2.3) times as long as broad; bracts mostly suborbicular to broadly elliptic (obovate in var. paludosa ), the largest ones 6.5–16 × 3.5–13 mm; fruits small, 3.5–6 × 3.5–6 mm when dry; corolla (except sometimes in var. paludosa ) glabrous outside or pubescent only at the apex of the lobes ........ 9

8a. Calyx lobes narrowly ovate to elliptic, (2–)2.5–6 × 0.7–2.5 mm, acute to obtuse at apex, plain white or pale green, more than twice as long as broad; bracts ovate to obovate, the largest ones 5.5–11.5(–14) × 2.2–4.5 mm; fruits larger, 5–9 × 5–8.5 mm when dry; corolla lobes and upper part of tube pubescent outside ( Cameroon to Republic of Congo) ................................................................. 8. S. segregata

9. Inflorescence with a few much enlarged bracts occurring at irregularly scattered nodes, the other bracts much smaller ( Cameroon to D.R. Congo) ............................... ..................................... 3b. S. floribunda var. anisostegia

9a. Inflorescence with bracts becoming gradually smaller and narrower towards the ultimate ramifications ............. 10

10. Bracts obovate, densely pubescent on both sides (NE Gabon and D.R. Congo) .............. 3c. S. floribunda var. paludosa

10a. Bracts suborbicular to broadly elliptic, glabrous or with very sparse hairs ......................................................... 11

11. Leaf secondary veins few (8–13) and widely spaced; twigs glabrous or with very sparse hairs; leaves glabrous except for sparse hairs on veins (S Cameroon to Gabon, mostly coastal) ....................... 3d. S. floribunda var. paucinervis

11a. Leaf secondary veins more numerous (15–25) and rather close; twigs densely pubescent; leaves rather densely pubescent on the veins, and often (but more sparsely so) between them ( Nigeria to Gabon) ................................. ...................................... 3a. S. floribunda var. floribunda