Revision of the genera Myrianthus and Musanga (Moraceae) by G. de Ruiter n Abstract. The African members of the Conocephaloideae are revised. Musanga comprises two species: M. cecropioides and M. leo-errerae. In Myrian- thus seven species are recognized: M. arboreus, M. holstii, M. preussii (with and M. M. ssp. preussii ssp. seretii), libericus, serratus (with var. serratus and and var. letestui), M. cuneifolius. M. serratus var. letestui is described as new. In of the Moraceae the African Engler’s system (1889) two genera and with the Myrianthus Musanga, together neotropical genera and and the Poikilo- Cecropia, Coussapoa, Pourouma Asiatic genus constituted the spermum (= Conocephalus), subfamily Conocepha- loideae. Chew Wee-Lek (1962) suggested transferring the small- seeded and genera Cecropia, Coussapoa, Poikilospermum, Musanga but retained the to the Urticaceae, big-seeded genera Myrianthus and Pourouma in the Moraceae. Corner (1962) transferred the whole basis subfamily Conocephaloideae to the Urticaceae, mainly on the of the similarities the characters of the in ovary : a simple stigma attached ovule. and a basally orthotropous However, distributing the the over genera assigned to subfamily Conocephaloideae two families be because of the anatomical and can hardly justified, many morphological features they have in common (cf., for example, Renner 1907; Erdtman 1952; Lebacq 1950; Normand 1950). No for such distinct the suggestion transferring a group as Conocepha- be made without first tho- loideae to another family can properly roughly examining the delimitation of the Moraceae and Urticaceae. Utrecht (*) Institute for Systematic Botany, State University, (The Netherlands). — Manuscript received March 25, 1976. 472 The is based material in the herbaria present study on following ; B, BR, BM, COI, E, FHO, G, K, L, LISC, LISU, S, U, UPS, WAG. 1. Myrianthus P. de Beauvois, Fl. Oware 1 : 16 (1805); Bâillon, Hist. 214 PI. 6 : (1875-1876); Bentham & Hooker, Gen. Pi. 3 (1) : Pflanzenfam. 379 (1880); Engler in Engler & Prantl, Nat. 3 (1) : Afr. Pfl. 94 (1889); Engler, Monogr. 1 1 Moraceae] : 37 (1898); Rendle in El. Afr. 6 230 — Prain, Trop. (2) : (1917). Type species : M. arboreus P. de Beauvois. Ann. Dicranostachys Trécul, Soi. Nat., Bot., set. 3, 8 : 85 (1847); 6 Bâillon, Hist. Pi. : 214 (1875-1876); Engler, Monogr. Aft. Pfl. 1 37 — D. [Moraceae]: (1898). Type species : serrata Trecul. Myrianthus sect. Dicranostachys (Trecul) Engler, Monogr. Afr. Pfl. 1 [Moraceae] : 37 (1898). Dioecious shrubs or trees with stilt-roots or lianas. Leaves spirally arranged, simple to palmately compound, stipules fused, (sub)am- plexicaul, glabrous inside. Inflorescences paired in the axils of the leaves, bracteate, pedunculate; the staminate ones repeatedly dicho- tomously branched, bearing the flowers close together on the ultimate to more proximal branches, perianth with (3-)4, more or less imbricate tepals, stamens 3-4, filaments straight in the bud, free or basally connate, anthers extrorse; pistillate inflorescences globose- flowers several capitate, to many, basally connate, perianth tubular, ovule and 2-3-lobed, ovary free, orthotropous basal, stigma simple; fruit adnate the : exocarp fleshy, to fleshy, yellow to orange-red coloured perianth, endocarp woody; seed big, without endosperm, testa membranaceous, cotyledons equal and plane, radicle short and apical. History The established Palisot de Beauvois genus Myrianthus was by (1805), who described M. arboreus. In 1847 Trecul described Dicra- with D. serrata he the related nostachys, ; regarded genus as to The Baillon Myrianthus. two genera were kept separated by (1877), but were united by Bentham & Hooker (1880). Remarkably enough they described the ovule as apical and pendulous, while Baillon (1877) correctly described the ovule of Myrianthus as basal and orthotrophous, as did Trecul for Dicranostachys. Engler took over 473 this error in his treatment of the Moraceae in « Die natiirlichen Pflanzenfamilien he corrected his » (1889). However, it in mono- graph of African Moraceae (1898) and at the same time subdivided Myrianthus, in which he distinguished 6 species into the sections Eumyrianthus and Dicranostachys on account of (partly presumed) differences in the pistillate flowers, infructescences, and leaves. In and material Engler’s monograph (cf. p. 37, 38, plate XVI, fig. a) of M. holstii was assigned to M. arboreus, as the two species were separated on the basis of the degree of incisions of the leaves. Rendle (1917) maintained the subdivision of Myrianthus and distri- buted the ten species described at that time over the two sections. Later subdivision of seldom on this Myrianthus was applied. Up to the 12 have been described and 7 have present, Myrianthus species commonly been distinguished. Morphology Habit Except for M. scandens, a liana with air-roots, all species are trees or shrubs. The former habit is characteristic for M. arboreus and M. holstii, but it also occurs in M. serratus and M. preussii. The reach of 20 with in trees may a height m, as commonly met M. for M. seretii of 24 and holstii, although preussii ssp. heights m 30 m are (possibly incorrectly) mentioned. M. cuneifolius is found mainly as a shrub or small tree (up to 3.5 m tall). Leaf The leaves from and vary simple entire to palmately compound, with 5-7 leaflets. have leaves which Seedlings simple gradually pass into the leaves characteristic for the adult specimens. Palmately M. compound leaves are characteristic for arboreus, M. holstii, and M. preussii and occur commonly in M. cuneifolius. Normally, M. serratus, M. libericus, and M. scandens have simple leaves. In M. serratus the leaves are usually simple, but sometimes 3-5-fid. These 3-5-fid leaves in M. libericus in are common and may occur M. scandens in M. holstii. and even Depending on the leaf shape the venation is pinnate or palmate. 474 Petiole The dimensions of the petioles depend on the dimensions of the In M. leaf blades. arboreus, M. holstii, and some specimens of the sulcate M. serratus petioles are coarsely and ribbed, but almost even in the small-leaved species. In M. libericus the petioles formed at the beginning of the growing period are relatively long, gradually becoming shorter towards the end of the growing period. Stipules The stipules are usually caducous, but subpersistent in M. serra- serratus M. and M. The tus var. , cuneifolius, preussii ssp. preussii. M. M. long stipules of arboreus and holstii are fully amplexicaul and leave annular the other conspicuous scars; in species they are and leave annular The subamplexicaul inconspicuous not fully scars. stipules are glabrous inside. Indument The characters of the indument are important for identification have be examined the the purposes. They to on younger parts, as indument with The hairs unicellular usually disappears age. are or The unicellular hairs colour pluricellular. vary in dimensions, shape, and insertion. On the lower leaf surface, especially the areoles, the indument is arachnoid. The pluricellular (glandular ?) hairs are often more or less irregularly globose-capitate, sessile or stipitate, in and yellow-brown or dark red. They are inconspicuous herbarium the of M. arboreus M. material, except on younger parts and holstii. Staminate inflorescence The peduncle bears 2-7 more or less equal primary branches. Each one branches repeatedly (up to 7 times) and dichotomously. The flowers borne dense the dichotomous are in groups on secondary ramification. The clusters of flowers be confined to the ultimate may branches (n) branches or may extend to more proximal (n-1 to n-4) flowers sometimes found the bifurcation (see fig. 1). Solitary are at of the branches. The bracts the flowers secondary among are usually and subcucullate the The other narrow at apex. bracts, usually situated on the bifurcations, are broader (often deltoid, broadly and obovate, or broadly ovate) plane or convex. 475 Staminate flower The is perianth rather variable. As a rule it consists of 4, more less or distinctly 2-merous, (sub)cucullate tepals. The tepals are free or basally connate. The filaments are free or connate. The dimen- sions of the floral parts show little variation; in M. holstii, however, they are distinctly greater. Fig. 1. — Scheme of the staminate inflorescence of Myrianthus. Pollen Pollen of M. serratus, M. arboreus, M. libericus, and M. preussii, treated the method by acetolysis (Erdtman 1960) and studied under a light microscope, seems to be uniform. Its description according to Reitsma’s terminology (1970) is as follows : Pollen class PIE : diporate. ratio : 1.15. Aperture : ecto-aperture — rather porus; indistinct, irregularly shaped, mostly circular to faintly elliptic; endo-aperture — identical with the ectoporus. Exine : thin; sexine : as thick as the exine; sexine and nexine decreasing towards the Ornamentation apertures. : psilate, tectate; columellae 476 fine. Outlines view — very : equatorial elliptic to rectangular, faintly acuminate, with convex to rhombic sides and obtuse angles; polar view — Measurements axis 13-18 circular to elliptic. : longest /t; exine about 1 axis of the about 2 ju.; longest aperture ft. Pistillate inflorescence The inflorescence is pistillate globose-capitate; a distinctly enlarged receptacle is seen only in M. arboreus. The number of flowers varies from 20 to 50 (80). The interfloral bracts are (sub)spathulate and usually basally adnate to the perianths. Pistillate flower The tubular is obovoid with flat perianth a apex in M. arboreus. but ovoid to conical in the other The almost free. species. ovary is Infructescence The infructescence reach diameter of than may a more 12 cm (as mentioned for M. arboreus and M. libericus). The fruiting perianth coloured and adnate the is yellow to orange-red to exocarp, forming less a more or fleshy layer round the woody endocarp. Lignification of the at the Because infructescences are often ovary begins apex. scarce in collections, they cannot always be completely described. Distribution M. holstii inhabits moist montane forests in East Africa. The other species are found in the lowlands of West and/or Central Africa, usually on moist soils and in secondary forests, at forest edges, along rivers, etc.