98 S.-Afr. Tydskr. Plantk., 1987,53(1) A new species of Canthium (Rubiaceae) from southern Natal and Pondoland Patricia M. Tilney and P.D.F. Kok* Science Department, Johannesbu(g College of Education, 27 St. Andrews Road, Parktown, 2193 Republic of South Africa and H.G.W.J. Schweickerdt Herbarium, Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa Accepted 22 September 1986 Canthium vanwykii Tilney & Kok, a fairly common shrub or small tree endemic to the sandstone region of southern Natal/Pondoland is described. The species is mainly confined to forest margins and can readily be distinguished from the other southern African species of Canthium Lam. s.str. chiefly by a combination of inflorescence and floral characters. It appears to be most closely related to C. ciliatum (Eckl. & Zeyh.) Kuntze from which it differs in several of these and other features. Diagnostic characters for C. vanwykii include the many-flowered inflo­ rescences, essentially pentamerous flowers, a relatively short and funnel-shaped corolla tube, corolla lobes which exceed the length of the corolla tube and distinctly petiolate and usually widely ovate to widely elliptic leaves with pubescence largely restricted to the midrib, petiole, and principal lateral veins. Canthium vanwykii Tilney & Kok, 'n taamlik algemene struik of kleinerige boom endemies in die sandsteengebied van Suid-NataliPondoland word beskryf. Dit is hoofsaaklik 'n woudrand-spesie wat geredelik op grond van veral bloeiwyse- en blomkenmerke van ander Suider-Afrikaanse spesies van Canthium Lam. s.str. onderskei kan word. Die spesie is moontlik naverwant aan C. cilia tum (Eckl. & Zeyh.) Kuntze waarvan dit op grond van verskeie van hierdie asook ander kenmerke onderskei kan word. Diagnostiese kenmerke vir C. vanwykii sluit in die meerblommige bloeiwyses, essensieel pentameriese blomme, relatief kort tregtervormige kroonbuis, kroonlobbe wat langer as die kroonbuis is en duidelik gesteelde en gewoonlik breed-eierronde tot breed-elliptiese blare met harigheid beperk tot die petiool, hoofaar en opvallendste syare. Keywords: Canthium, endemism, Rubiaceae, taxonomy *To whom correspondence should be addressed Introduction Branchlets green, puberulent when young, becoming greyish­ A change in generic limits has recently been proposed for brown and essentially glabrous with age. Leaves opposite, African taxa included Canthium Lam. s.l. (Bridson 1985). decussate, petiolate; lamina usually widely ovate to widely For southern Africa it entails the retention of Canthium elliptic, occasionally subrotund to rotund, (12 - )22 - 30( - 65) in a narrow sense and a reinstatement of the segregate genera mm long, (8 - ) 13 - 20( - 60) mm wide, base rounded to Psydrax Gaertn. and Keetia Phil!. Based mainly on morpho­ bluntly attenuate, very rarely subcordate, apex usually obtuse, logical evidence, Bridson's proposals have subsequently occasionally ± rotund or acute, margin entire, glabrous received overwhelming support from an anatomicallpalyno­ above, lower surface puberulent over midrib (becoming logical study (Tilney 1986). The latter study also confirmed increasingly sparse away from petiole), usually sparsely the presence of a new species of Canthium s.str. endemic to puberulent over larger secondary veins, remainder of lamina the sandstone region of southern Natal and Pondoland. This nearly always glabrous, dark green and shiny above, often is another tree addition to the growing list of mainly woody becoming conspicuously yellowish-green towards autumn and taxa narrowly confmed to this remarkable centre of endemism winter, paler green and dull below, upper surface often drying (Van Wyk 1985). The present paper provides a description to a brownish colour in herbarium specimens; midrib slightly of the new species and a discussion of its diagnostic features. raised above, prominently raised below, principal lateral veins The new species is named after A.E. van Wyk, Curator opposite or occasionally alternate, 3 - 4( - 6) pairs, widely of the H.G.W.l. Schweickerdt Herbarium, University of spaced, forking and looping usually c. 1,5 mm from the Pretoria, who in recent years has focussed attention on the margin; domatia usually present in the axils of some of the uniqueness of the southern NatallPondoland flora by de­ principal lateral veins, occurring as hair tufts in depressions scribing several new species endemic to this region. (visible as prominences on the upper surface), absent from some leaves; petiole 2 - 5( - 8) mm long, puberulent; stipules Description large, deltoid, broadly based and tapering to a fine point, up Canthium vanwykii Tilney & Kok, sp. nov., ali­ to c. 4 mm long, brown, puberulent on outer surface, and quantum similis C. ciliato, a qua differt i.a. multifloris sericeous at base on inner surface, marcescent to caducous. inflorescentiis, breviore et infundibuliforrni tubo corollae, lobis Inflorescences up to 50-flowered (usually 8 - IS-flowered) corollae longioribus quam tubo; foliis plerumque late ovatis cymes, axillary, subfasciculate; peduncle up to 12 mm long, ad late ellipticis, et praecipue petiolo ac nervo principali puberulent; pedicels 2 - 4( - 7) mm long, puberulent; bracts nervisque secundariis puberulis. inconspicuous. Flowers bisexual, actinomorphic, epigynous, pentamerous with a few flowers occasionally tetramerous or TYPUS - Natal: Along a tributary of the Uvongo River, Mr H. very rarely hexamerous. Calyx green, shortly toothed, teeth Wichmann's Farm, Van Wyk 5110 (PRU, holotypus; PRE, c. 0,5 mm long, deltoid, puberulent. Corolla yellow to isotypus). greenish-yellow, tube (1- )1,5( -1,8) mm long, infundibular, Evergreen or semi-deciduous much-branched shrub or me­ notably widening towards the mouth of the tube (base of dium-sized tree up to 6 m tall, unarmed or armed with short lobes), mouth of tube with a fringe of whitish hairs, lobes axillary spinescent branchlets; bark dark grey and smooth glabrous, initially spreading, becoming reflexed with age, when young, becoming light grey and rough with age. (2,0 - )2,3 - (2,8) mm long, (1- )1 ,2( -1,4) mm wide at base, S. Afr. J. Bot., 1987, 53(1) 99 3. Figure 1 Canthium vanwykii. I. flowering branchlet, x 1; 2. leaf showing lower surface with domatia (left) and upper surface (right), x 2; 3. flower, x 7; 4. one-, two- and three-seeded fruits, x 3 (I- 3 from Van Wyk 5110; 4 from Van Wyk 7172). 100 S.-Afr. Tydskr. Plantk., 1987, 53(1) deltoid, apex thickened. Stamens alternipetalous, inserted just species for the presence of this sandstone flora. It has, below the rim of the corolla tube, shortly exserted; filaments however, not yet been recorded from the extreme southern c. 0,5 mm long; anthers c. 0,7 mm long, apex acute, base parts of this southern Natai/Pondoland sandstone 'island' (the sagittate, introrse, subbasifixed. Disc annular, entire, slightly Ntsubane area). raised and shiny. Ovary globose-obconical from the outside, 3-locular, with one ovule in each locule; style c. 2,5 mm long, terete, shortly (c. 1,3 mm including stigma) exserted; stigma 3-lobed. Fruit drupaceous, more or less ovoid, up to 10 mm long, 1 or 2( - 3)-lobed, ripening to dark brown or blackish, .,...../". '""--- 1 or 2( - 3)-seeded (Figure 1). "­ ,-./.~.-.- Flowers produced during spring (mainly October) with ( fruits ripening from about December. Distribution and habitat Canthium vanwykii is known only from the sandstone (Natal Group - previously classified as Table Mountain Sandstone) region of southern Natal and Pondoland (Figure 2). Its habitat is usually rocky and the soils shallow, sandy, acidic and poor in plant nutrients. Plants of the new species occur mainly on forest margins, more rarely in fire-protected crevices of rocky outcrops in ~h-A--kI /~ grassland. Canthium vanwykii is a hardy species, often conspicuously present at the exposed upper cliff margins of r----r----t---~=~~-t~----PL---.m+,-~O-I-,-I+I-I---t-ll-o--J 31 forested river gorges. In contrast to the scarcity of many other of these sandstone 16· 30· I 31· endemics, Canthium vanwykii is fairly common over most of this region. It may therefore be considered a good indicator Figure 2 The known geographical distribution of Canthium vanwykii. Figures 3 & 4 Comparison of flowering twigs in Canthium vanwykii and C. ciliatum. 3. C. vanwykii; note almost glabrous leaves with obtuse apices, multi flowered inflorescences, flowers with sepals minute and with a relatively short corolla tube which is funnel-shaped and not constricted at the mouth (Tilney /60). 4. C. ciliatum; note leaves with the lamina hairy and with acuminate apices, single-flowered inflorescences, flowers with sepals linear and recurved with a relatively long corolla tube which is notably constricted at the mouth (Tilney 183). Scale line = 10 mm. S. Afr. J. Bot., 1987, 53(1) 101 Discussion a relatively large range of intraspecific anatomical variation. Canthium vanwykii is a clear-cut species easily distinguished Amongst the differences observed was the thickness of the by a combination mainly of inflorescence and floral cha­ leaf blade. In the 21 specimens of C. ciliatum examined the racters. These include the multiflowered inflorescences, range obtained was (70 - )130 - 190( - 440)J.!m, whereas in C. predominantly pentamerous (rarely tetramerous or hexa­ vanwykii the range was (170 - )220- 310 J.!m. Apart from the merous) flowers, a relatively short corolla tube with the mouth midrib and principal lateral veins, the lamina is nearly always not constricted - thus rendering the whole disc visible from glabrous in C. vanwykii. Characteristically the whole lamina above - and relatively long corolla lobes exceeding the length surface is pubescent in C. cilia tum. of the tube. The leaves are usually broadly ovate or broadly Studies of the pollen grains (Anastassiades 1983; Tilney elliptic and distinctly petiolate. Pubescence is largely confined 1986) did not reveal any significant differences between C. to the petiole, the midrib and usually also to some of the larger vanwykii and C. ciliatum. The grains of these species are secondary veins. The hairs, however, are minute and scarcely similar in many respects to the other native members of visible to the unaided eye.