Rudgea cornigera Bremekamp (1934: 304)

Lachenaud, Olivier, Bruniera, Carla P. & Zappi, Daniela C., 2022, The Rudgea hostmanniana complex (Rubiaceae) in the Guiana Shield region, Phytotaxa 561 (3), pp. 219-242 : 227-229

3. Rudgea cornigera Bremekamp (1934: 304) . Fig. 1C , 2C .

Type:— SURINAME. Watramiri , 22 June 1910 (fl.), B. W. [=Bureau v.h. Boschwezen] 4728 (lectotype, first-step designated by Steyermark (1967: 4166), second-step U! [ U0006284 ], here designated; isolectotypes BR [ BR0000024941754 ]!, G! [without barcode], MO [MO-797272, MO-797610]!) .

Much-branched shrub 2–6 m tall, main stem up to 4 cm in diameter; twigs glabrous, 3–4 mm thick, soon covered with a pale buffish-straw bark. Stipules 6–12 × 5–12 mm, glabrous, marcescent and soon corky, consisting of a short basal sheath 3–5 mm long (usually split at flower-bearing nodes) bearing on each side of the node 1–2 linear lateral appendages 2.5–5 × 0.5–1 mm, and a central keel 4–9 × 2–4 mm, about equalling the latter and divided into 4–7 often unequal appendages 1–3.5 mm long, the lateral ones usually connate, longer than the central ones. Leaves opposite; petioles 2–8 mm long, glabrous; blades elliptic to slightly oblanceolate, (8.5–)10.2–22 × (1.7–) 2.8–9.6 cm, gradually narrowed towards an obtuse base, strongly acuminate at apex, very thick, entirely glabrous, drying greyish-green to olive brown; midrib concave above; secondary veins 8–11 on each side of midrib, usually strongly ascending, forming loops well away from the margin; tertiary veins lax and slightly prominent in dry specimens (probably invisible in the fresh state); domatia absent. Inflorescences terminal, in lax to fairly condensed hemispherical panicles, 2.4–12.5 cm long, erect, sparsely spreading-puberulous; peduncle terete, 0.8–6.5 cm long; branched portion 1.5–6 × 1.8–7 cm; secondary branches (2–)3–4 per node, 0.3–2 cm long; bracts 1.5–3 × 0.3–1.5 mm, triangular to subulate, entire or irregularly dentate, shortly pubescent especially on the margins. Flowers sessile, 5-merous, heterostylous, fragrant. Hypanthium obconical, 0.5 mm long, glabrous. Calyx tube extremely reduced, lobes triangular to subulate, 0.7–1.2 × 0.3–0.5 mm, acute at apex, shortly pubescent especially on the margins. Corolla white, hypocrateriform; tube cylindrical to narrowly funnel-shaped, 5–7 mm long, 0.8–1.3 mm wide at base, 2–4 mm wide at mouth, glabrous outside, with a ring of dense short hairs at the insertion of the stamens inside; lobes narrowly elliptic, 3–5 × 1–2.5 mm, puberulous outside at least near the apex, papillose inside, with obtuse dorsal cornicula 0.5–1 mm long. Stamens subsessile with anthers tips reaching the corolla mouth in long-styled flowers, or fully exserted with filaments 1 mm long in short-styled flowers; anthers 1.8–2 × 0.4 mm. Disk shortly cylindrical, 0.5 mm long, glabrous. Style just as long as corolla tube in both morphs, 5–6.5 mm long, glabrous; style branches 1 mm long, stigmatic surface papillose. Fruits obovoid, 7–11 × 4.5–8 mm when dry, brown when immature, orange to red when mature, glabrous, sessile, crowned with persistent calyx 1.5–2.5 mm in diameter. Pyrenes plano-convex, hemi-obovoid, 7.5–8 × 4.5–5 mm, dorsal side with 3 ridges, smooth between the ridges, ventral side smooth. Seeds with a deep T-shaped ventral furrow.

Distribution and ecology: —Northern Suriname and central Guyana ( Fig. 5 ). The species occurs in dry forest, mixed evergreen forest, Mora forest, and rocky areas along creeks, often on brown sand, 0–700 m elevation.

Phenology: —Specimens with flowers were collected in May (buds), August and October-December; and with fruits in all months of the year, except June and August.

Notes: —This species closely resembles Rudgea hostmanniana , and the two have often been regarded as synonyms in herbaria, although the synonymy seems not to have been officially published. Steyermark (1967: 399) in his dichotomous key separated them only by the size of the petiole, supposed to be 2–5 mm in R. hostmanniana and 8–15 mm in R. cornigera . In fact, the two species must have been inverted in the key, since R. cornigera has petioles not exceeding 8 mm in length, usually shorter than those of R. hostmanniana . A detailed study of the material available showed that petiole length is not a reliable character to separate the two taxa; however, more significant differences exist (see Table 1 ) and R. cornigera should therefore be maintained as a separate species. It is also similar to R. tanaosepala , which has a partly overlapping geographic range (for differences see the key and Table 1 ).

The heterostyly in Rudgea cornigera is of an unusual type, where the style is about as long as the corolla tube in both morphs, and only the position and length of the stamens varies. This is another difference with R. hostmanniana , which shows reciprocal heterostyly.

Bremekamp (1934: 304) cited several syntypes in the original description of Rudgea cornigera : B.W. 1862, 2227, 2457, 2662, 3356 & 4728, Samuels 430 and Versteeg 515. Steyermark (1967: 416) cited B.W. 4728 as type, which is to be interpreted as a first-step lectotypification, but did not specify the herbarium of deposit. The sheet in U (barcode U0006284 ), where Bremekamp worked, is here selected as a lectotype.

Additional Specimens Examined: — GUYANA. Holmia, November 1909 (fl.), A. W . Bartlett 8731 ( K); Kamarang to Waramadou trail, 5°50’N, 60°39’W, 23 January 1996 (imm. fr.), D. Clarke 789 ( CAY, U); Region Potaro-Siparuni, Paramakatoi, 0.5-4 km from trail to Maikwak & Kowatipu, 4°43’N 59°42’W, 22 February 1996 (imm. fr.), D. Clarke & Grose 1197 ( U); 20 m from Saydak creek , 11 April 1979 (fr.), P. J . Edwards 1220 ( K, P); Mabura region, YaYa creek , 5°20’N, 58°30’W, 25 November 1992 (fl. buds), R. C . Ek 586 ( U); 85 miles Bartica – Potaro road, 3 November 1947 (fl. buds), D. B . Fanshawe in Forest Department 5545 ( K); Upper Demerara River , September 1887 (fl. buds & fr.), G. S . Jenman 4054 ( K); Pakaraima Mts , Kamarang, 5°52’N, 60°38’W, 8 November 1979 (fl.), P. J. M . Maas & L. Y. T . Westra 3973 ( K, U); Mabura Hill , 5°19’N, 58°28’W, 27 October 1981 (fl.), P. J. M . Maas, E. A . Mennega & B. J . H. ter Welle 5884 ( K, U); Blackwater Creek camp, 5°12’N, 59°10’W, 23 May 1991 (fr.), T . McDowell, C. M . Kelloff & A . Stobey 4903 ( CAY); Potaro River, left margin on portage trail on second set of rapids above Chenapou , 5°0’50.3”N 59°39’3.1”W, 18 March 2014 (fr.), F. A . Michelangeli, Z . Narine, J . Isaacs, N . Carter & P . Lewis 2293 ( NY); Mabura Hill Area , 5°20’N 58°40’W, 6 June 1986 (fl.), J. J . Pipoly & R . Boyan 7593 ( CAY, P); Pakaraima Mts, Mazaruni River, 17 GPS miles W of Imbaimadai to Kamarang , 5°42’58”N, 60°32’34”W, 4 February 2004 (fr.), K. M . Redden, C . Perry, C . Paul & M . Lyle 1680 ( P); Mazaruni River above ABC Falls , 6°4’N, 60°37’W, 16 February 2004 (imm. fr.), K. M . Redden, M . Lyle, R . Williams, C . Perry & C . Paul 2807 ( CAY, K); Mabura Hill, 180 km SSE of Georgetown, Ya-ya Creek, 11 March 1988 (fr.), H. ter Steege, P. de Jager, J.M.C. Potters & W.N.J. Ursem 238 ( U); mouth of Suru-a-gupuh River , 12 September 1960 (fr.), S. S . Tillett & C. L . Tillett 45389 ( K, U) .

SURINAME. Palisadeweg , 17 October 1949 (fl. & fr.), B . B .S. 278 ( K, U); Bosch Reserve Watramiri, 5 December 1916 (fr.), Bureau v.h. Boschwezen 2502 ( U); Bosch Reserve Zanderij I , 17 October 1917 (fl.), Bureau v.h. Boschwezen 3356 ( INPA, U); Watramiri , 2August 1916 (fallen fl.), B . W . 2227 ( L); Watramiri , 8 February 1917 (imm. fr.), B . W . 2662 ( BR, G); Mapane , 9 June 1970 (fl. & fr.), C . J . Gieteling 104 ( WAG); Forest Reserve Zanderij 1, 31 July 1933 (fr.), J . Lanjouw 353 ( INPA, K, U); Jodensavanne – Mapane Kreek area ( Suriname R.), 16 March 1953 (fr.), J . C . Lindeman 3519 ( U); ibid., 5 May 1953 (fr.), J . C . Lindeman 3805 ( U); Coppename River , near Bitagron, along S road of Surocto base, 6 August 1954 (fl.), J . C . Lindeman 6437 ( U); Along Rijsdikweg , ca. 25 km S of Paramaribo, 28 October 1954 (fl. buds), J. C. Lindeman 6625 ( U); Kabo , distr. Saramacca, October 1978 (fr.), J . Procter 4769 ( U); Forest of Zanderij , 31 May 1916 (fl. buds), J . D. Samuels 430 ( K, L, P); hoog droogl. bos bij Kamp 8, 23 December 1955 (fl.), J . P . Schulz 7539 ( U); pr. Paramaribo, June 1904 (fl. buds), G . M . Versteeg 515 ( U); “e regione Para ”, s.d. (fr.), H . R . Wullschlaegel 994 ( BR) .

Figures

FIGURE 1. Stipules in the Rudgea hostmanniana complex.A, R. bolivarensis; B, R. coussareoides; C, R. cornigera; D, R. hostmanniana subsp. hostmanniana; E, R. maypurensis; F, R. tanaosepala. A from Mutchnick 1620 (K), B from Diaz et al. 7727A (K), C from Schulz 7539 (U), D from Lachenaud 1011 (BR), E from Williams 12972 (K), F from Clarke & Hoffman 584 (U). Drawing by O. Lachenaud.

FIGURE 2. Calyx and corolla in the Rudgea hostmanniana complex.A, R. bolivarensis, calyx; B, R.coussareoides, calyx; C, R. cornigera, flower bud; D, R. hostmanniana subsp. hostmanniana, flower bud; E, R. maypurensis, flower bud; F, R. tanaosepala, flower bud. A from Henkel 5675 (U), B from Liesner 24924 (K), C from Procter 4769 (U), D from Lachenaud 981 (BR), E from Plowman 13733 (K), F from Clarke & Hoffman 584 (U). Drawing by O. Lachenaud.

FIGURE 5. Distribution of Rudgea billietiae (black triangles), R; bolivarensis (grey circles), R. cornigera (black squares), R. pungens (grey squares) and R. tanaosepala (grey triangles).