BLUMEA 23 (1976) 177—188 A revision of the tribe Cephalantheae (Rubiaceae) C.E. Ridsdale Summary The tribe Cephalantheae is here reinstated; a full taxonomic treatment of all species is given, including a The architecture and relations discussed. key to all species. systematic are Introduction During the revision of the Naucleeae sensu K. Schumann (1891) for Flora Malesiana the all the extra-Malesian characters of component taxa of tribe, including the groups, were re-evaluated. It became evident that the tribe as conceived by K. Schumann is a heter- also concluded that the tribe was ogeneous group. Bemekamp (1966) heterogeneous. At least three genera, Cephalanthus, Mitragyna, and Uncaria, and possibly also Anthocephalus, limits Naucleeae conceived work. do not fall within the of the as in the present This paper deals with Cephalanthus which is transferred back into a monotypic tribe. The treatment of the literature is not completely uniform, for the Asiatic taxa full literature references and complete distribution data are given, but for the non-Asiatic taxa only the basic literature is cited and only general distribution given. SYSTEMATIC RELATIONSHIPS The genus has had a chequered history and for the last hundred years has generally been considered to occupy an isolated position in the Naucleeae sensu K. Schumann. earlier has also been the where At an time it placed in Spermacoceae, it certainly does not noted It has been in belong, as by Bremekamp (1966). segregated a separate tribe Cepha- lantheae by Humbold, which originally also included Morinda, but some later authors and stated excluded Morinda. Bremekamp (1966) has questioned the position of the genus that it should be studied in more detail. The pendulous solitary ovules suggest a strong relationship withthe Naucleeae(Mitragyna and Uncaria excluded) but in this tribe there is no arillus. Haviland records arils for Nauclea (Sarcocephalus) but I have not been able to confirm this observation. Phytochemically is in Uncaria there a strong affinity with the alkaloids found Mitragyna and (Phillipson & this close with these but in Hemingway, 1974); suggests a relationship genera, Mitragyna and Uncaria the ovules are vertically imbricate on a pendulous placenta and there is no arillus. The wood deviates from the other members of the tribe anatomy Naucleeae K. Schumann (Koek-Noorman, 1970). relic The distribution suggests a group, particularly as the single African species seems isolated the the and to occupy an position in genus, American Asiatic taxa being closely related, mutually. *) B. A. KrukofF botanist of Malesian Botany, Rijksherbarium, Leiden. VOL. No. 178 BLUMEA 23, 1, 1976 The relationships of the tribe are clearly with the Naucleeae or the Cinchoneae. The problem of relationships is centred around the delimitation of the tribes. The Naucleeae tribe Shaw have been considered to be a homogeneous by most botanists, Ariy (1973) Wernham in the as a even following considering group separate family; only Bremekamp (1966) has questioned this concept. A re-examination of the component taxa has shown that the only character they have in common is the aggregation of the flowers into a in sphaerical head. This feature occurs spasmodically many tribes and cannot be considered of great significance. Besides Cephalanthus, two other genera must also be excluded from and Both the Naucleeae: Mitragyna Uncaria. genera were considered by Haviland (1897) to occupy a distinctive position in the tribe and were placed into separate subtribes by him. The pendulous placentas bearing numerous vertically imbricate ovules, the nature of the and of the placentas, and the construction dehiscence fruit all indicate that the two genera have greater affinity with the Cinchoneae than with the Naucleeae. Evidence from phyto- chemistry in the nature of the indolealkaloids together with the similarities ofthe growth and form indicates between and organization a strong relationship Cephalanthus Mitragyna and Uncaria. In reappraising the characters of these two genera and the tribe Cinchoneae is that the Schumann it became apparent that there a possibility Cinchoneae sensu K. are still of taxa. The of this still also a heterogeneous assemblage investigation problem is in the be of initial stage and at the momentlittle can said over the interrelations the remainder of ofthe Cinchoneaeand the Cephalantheae. However, the exclusion Mitragyna and Uncaria from the Naucleeae (Ridsdale, 1975) results in Cephalanthus having a low level of relation- ship with the Naucleeae s.s. ARCHITECTURE the literature the leaf leaves In arrangement is variously given as in pairs or 3—4- verticillate. In branches found mounted in the herbarium the leaves are mostly either in whorl of three or four. pairs or in a Cephalanthus occidentalis Observation of Arboretum showed that there dimor- a living plant in Wageningen is a phic branching system. The orthotropic axis basically has the leaves arranged in three's (sometimes one memberis suppressed or reduced), in the axis of each leaf are differentiated buds. The serial to the serial upper bud, supra-axillary in origin, gives rise plagiotropic the lower of system; is a dormant(=proleptic) bud the orthotropic system. The plagio- unbranchedwith the leaves tropic system is non-horizontaland always in pairs; flowering buds sometimes develop in the axils of these leaves. Flowering is both terminal and lateral The that on both the orthotropic and plagiotropic systems. consequence of this is flowering the terminates the growth of the plagiotropic system and flowering on orthotropic buds of that The system results in the development of the proleptic system. orthotropic thus branches after each system repeatedly 3 or 4 times flowering period. Cephalanthus natalensis the also three's and the has Here orthotropic system is arranged in plagiotropic system the leaves arranged in pairs. However, the plagiotropic system is branched, the lateral branches from the leaf axils. Below the lateral branch arising in a supra-axillary position dormant bud both terminal no can be detected. Flowering is again and lateral on both systems. Ridsdale C. E. : Revision ofCephahntheae (Rubiaceae) 179 REFERENCES AIRY H. K. In C. A of and ed. SHAW, 1973. J. Willis, dictionary floweringplants ferns, 8: 779. C. E. B. BREMEKAMP, 1966. Remarks on the position, the delimitation and the subdivisions ofthe Rubiaceae. Acta Bot. Neerl. 15: 1—33. G. D. A revision of tribe Linn. Soc. Bot. HAVILAND, 1897. the Naucleeae (Rubiaceae). J. 33: 1 —94, pi. 1 —4. A contribution the wood of and Naucleeae KOEK-NOORMAN, J. 1970. to anatomy Cincboneae, Coptosapelteae (Rubiaceae). Acta Bot. Neerl. 19: 154—164. S. R. HEMINGWAY. PHILLIPSON, J. D., & 1974. Indole and oxindole alkaloids from Cephalanthus occidentalis. Phytochem. 13: 2621. C. E. A RIDSDALE, 197J. synopsis of the African and Madagascan Rubiaceae — Naucleeae. Blumea 22: 541—553- K. In Die SCHUMANN, 1891. Rubiaceae. Engler & Prantl, natiirlichen Pflanzenfamilien, ed. I, 4, 4: 55 —60. CEPHALANTHEAE H. B. K. Gen. Cephalantheae [Nov. Sp. 3 (1818) 379, nom. prov. (as 'Sectio')] ex Kunth, Synop. PI. Aequinoct. Intr. 4 (1824) 37 (as 'Sectio'); Cham. & Schlecht., Linnea 4 (1829) 147 (as 'Sectio'); Lindl., Nat. Syst. Bot. — Endl., (1830) 204. Subtribe Cephalanthinae DC., Prodr. 4 (1830) 538 (as ‘Cephalantheae’); Gen. PI. Linn. (1838) 530; Ench. Bot. (1841) 271 (both as ‘Cephalantheae’); Havil., J. Soc. Bot. 33 (1897) 21 (as ‘Cephalanthidae’). shrubs Growth differentiated: axis with leaves Erect or trees. axes orthotropic 3- or 4-verticillate (sometimes one reduced or suppressed); plagiotrpic axis with leaves in terminal pairs. Stipules interpetiolar, apex with or without a black gland. Inflorescences and axillary on plagiotropic and orthotropic shoots, in compact heads, heads not sur- rounded by reduced leaves or stipules. Receptacle pubescent, interfloral bracteoles lobes sometimes with smaller present. Hypanthium tubular; calyx short, 4, a 5th one. Corolla hypocrateriform to infundibular, lobes spreading, in the bud (sub) imbricate. Stamens inserted in the throat ofthe corolla, filaments short, anthers dorsifixed, bicuspid at the base. Style filiform, exserted from the corolla; stigma capitate to clavate. Ovary 2-celled, ovules solitary, apically attached to the septum, pendulous, anatropous, funicle arillus. loose head of indehiscent with an Fruit a cocci. Monotypic. CEPHALANTHUS L. PI. ed. PI. ed. — Cephalanthus [Gen. I (1737) 60, no. 174] Sp. (1753) 5 (1754) no. 105. Type species: C. occidentalis L. Acrodryon Spreng., Syst. Veg. 1 (1825) 365, 386. — Lectotype species: (Merrill, 1935) A. orientale Spreng. Axolus Rafin., Sylv. Tell. (1838) 61. — Type species: A. angustifolius (Lour.) Rafin. E. Eresimus Rafin., Sylv. Tell. (1838) 61. — Type species: stellatus (Lour.) Rafin. of tribal For description genus see diagnosis. Distribution: 6 African. Pantropical, species: 3 American, 2 Asiatic, 1 KEY TO THE SPECIES ia. Calyx lobes narrowly triangular, apex long acuminate. Continental Asia I. C. angustifolius b. Calyx lobes oblong to elliptic and obtuse, or rarely shortly deltoid. America, Africa, Asia 2 BLUMEA VOL. 23, No. I, 1976 180 2a. Calyx (particularly the lobes) and hypanthium outside glabrous, sometimes with a few white hairs the base. America long_ at 3 b. Calyx (particularly the lobes) and hypanthium sparsely to mediumly pubescent or sericeous 4 Corolla 6 3a. generally over mm, style 6—10 mm, exserted. Leaves generally over 2 cm wide. N. and C. America. 2. C. occidentals 6 —6 b. Corolla up to mm long, style 4 mm, exserted. Leaves generally up to 2 cm wide. S. America. 3. C. glabratus and salicifolius 4a. Calyx hypanthium densely sericeous. C. America 4- C. b. and hypanthium sparsely to Calyx mediumly finely pubescent. Not in America . 5 ... 5a. Leaves generally over 5 cm long, Lobes ofcorolla not densely pubescent oninner side, sinuses usually with a black gland (such glands often present on calyx and stipules). Asia 5. C. tetrandra b. of corolla Leaves generally up to 5 cm long. Lobes densely pubescent on inner side, black glands absent from sinuses of corolla (also from calyces and stipules). Africa. 6. C.