A Generic Monograph of the Meliaceae

BLUMEA 22 (1975) 419—54.0 A generic monograph of the Meliaceae T.D. Pennington) and B.T. Styles Contents Introduction (by F. White) 419 Part I. General Discussion (by T. D. Pennington) Chapter 1. Taxonomic History 422 Chapter 2. Morphology 428 Chapter 3. Wood Structure 434 Chapter 4. Pollen 438 Chapter 5. Delimitation of Taxa 440 Part II. Conspectus of Genera (by T. D. Pennington and B. T. Styles) ofsubfamilies and and to 1 A. Family description; diagnoses tribes; descriptions keys genera —51 . 448 B. Keys to the identification of Genera 527 Acknowledgements 535 References 536 Index of Scientific Names 539 Introduction by F. White4) the the Ofall plant families Meliaceae is among more useful to man, chiefly for its high for with which be quality timbers and the ease some species can grown in plantations. Almost confined to the tropics, its species nevertheless pervade them, and occur, often conspicuously, in a variety of habitats from rain forest to mangrove swamp and semi- desert. the and For its size, family probably contains a wider range of floral fruit structures what other family is there such a diversity of than any comparable group. In primitive 5 ‘arillate ’ seeds, side-by-side with such an array of derived fruits and seeds, and still take the else be connected by intermediates? Or, to flower, where can found such a diversity of forms, from the minute, but structurally complex, flowers of Aglaia, often flowers of with no larger than a pin-head, to the moth-pollinated some Turraea, their slender staminal tubes reaching a length of 12 cm or more? This diversity is a source of rich material for the student of evolutionand of plant and animalinter-relationships, and provides an interest so often lacking in taxonomic studies. of But it is also a source taxonomic difficulty, as the taxonomic history of the group so clearly shows. With few mentioned of the a exceptions below, most genera currently recognized as *) Materials for a Monograph of the Meliaceae III. This series is being prepared at the Commonwealth Forestry Institute, Oxford, U.K. 2 ) Present address: Clarke's Farmhouse, Northmoor, Oxon, U.K. 3) Department of Forestry, Commonwealth Forestry Institute, Oxford, U.K. 4 ) Curator of the Herbaria, Botany School, Oxford University, U.K. 5 in wide Corner. In and ) Used the sense of my opinion careful comparative developmental studies are needed before the term can be applied more precisely. 420 BLUMEA VOL. 22, No. 3, 1975 Meliaceous have been regarded as such since the time of their discovery. But there has been persistent disagreement as to the numberof genera and their circumscription, and as the in and to best way to accommodate them tribes subfamilies. Even the number of has the de of families been uncertain from time of Jussieu (1789) to that Harms (1940). More than in other families, this uncertainty has been due to the diffuse and often of the reticulate nature variation, frequently aggravated by a lack of complete material. There is a quasi-absolute dearth of information on the functions of the structures con- cerned. Parallel evolutionary trends are numerous and have affected the flower and fruit independently. Complete material necessary for generic diagnosis has often been, and in work based some cases still is, lacking. Much of the material on which this is was specially collected in South-East Asia and tropical America by Dr. Pennington himself, and, to a lesser extent, by Dr. Styles and myself in Africa. Previous workers have often attached undue weight to single diagnostic characters, of anther insertion the tube of e.g. position on staminal or presence or absence endosperm. than These can now be shown to have arisen or been lost, as the case may be, more once, and to be poorly correlated with other characters. Some genera and most tribes can only combination of 'differential' defined be diagnosed by using a several characters (as by each of taken break White, 1962), one which, separately, may occasionally down, although the combination itself reveals a pronounced discontinuity. Thus, members of the Turraeeae cannot be distinguished from all other Meliaceae on the basis of a single character. character-states of have least few diagnostic Most typical Turraeeae at a exceptions in the also in tribe, and occur, at least occasionally, in other tribes, but always different combinations. The overall such all members markedly pattern, however, is that of the of thetribal character-states than excluded Turraeeaepossess many more any species. the Turraeeae is real definable Thus, objectively circumscribed, being based on a and gap in the variation for other subfamilies and pattern. Similarly genera. Only a selection of available characters has been used in the diagnoses of the tribes and in the and of in is keys to descriptions the genera. Further study, especially the field, reveal of for expected to complex syndromes confirmatory characters, the most part but well correlated and related the individually small, among themselves, functionally to methods ofpollination or means of dispersal. Many Meliaceae have unisexual flowers, but always with well-developed rudiments of the opposite sex. In contrast to most rudimentary structures, the shapes and positions of of within and these, relative to other parts the flower, are remarkably constant species genera and even tribes, and vary greatly between them. Compare, for instance, the flowers of Aglaieae (figs. 9—10) and Guareeae (figs. 11—14). Their function is to restrict it is of access to nectar, so that only available to the 'right kind' insect, which must adopt that make postures possible the transfer of pollen from fertile anther to receptive stigma. There are few observations on this, but I myself have seen how the small Hymenoptera which the of Trichilia havanensis visit flowers Jacq. are forced to insert their proboscides slots between the anthers or into very narrow antherodes, and, in so doing, pick up pollen from the male flowers and transfer it to the stigmatic surfaces of the female flowers. A glance at the illustrations in this generic monograph is sufficient to show that the precise of antherodes and relation other floral to configuration pistillodes in to parts is likely prove of considerable taxonomic value and evolutionary interest, when the floral biology of the family has been adequately investigated. The of claims certain genera to inclusion in the family have been frequently disputed time. up to the present Of the two most-controversial genera, Nymania and Ptaeroxylon, the shows that the former present study convincingly is Meliaceous and that the latter, T. D. Pennington & B. T. Styles: Meliaceae 421 had been White & must be as previously suggested (Leroy, 1959, 1960 a; Styles, 1966), excluded. Shortly after its discovery, the un-Meliaceous-looking Nymania was placed by de for Jussieu (1789) in his Melieae (as Aitonia). Some subsequent authors have sought a place it elsewhere. As recently as 1966, Airy-Shaw kept it in the monotypic family Aitoniaceae of Harvey & Sonder. In the present work it is shown that, both in its pollen grain and and secondary xylem, it clearly belongs, not merely to Meliaceae, but to the Turraeeae, floral that in its structure it is connected to Turraea by other genera, particularly by the discovered recently Malagasy genus, Calodecaryia. for Another monotypic South African genus, Ptaeroxylon, which was formerly prized its valuable timber, together with its Malagasy relative, Cedrelopsis, have sometimes been in sometimes At of this it known placed Meliaceae, elsewhere. the onset study, was that Ptaeroxylon differed markedly from all other Meliaceae, at that time investigated, in certain certain features of its pollen grain. Since a few other undisputed Meliaceae, notably of species Turraea, were also known to be anomalous in other pollen grain features, it was decided to regard the matter as sub judice until the pollen and wood-structure of the re-assessed. whole family had been adequately studied and the gross morphology It was Meliaceae then confirmed that Ptaeroxylon is distinct from all in its pollen grain and secondary xylem. The resemblances between the capsular fruit and winged seed of Ptaeroxylon and Swietenioideae prove to be superficial. Of the four subfamilies recognized here, the two largest, Swietenioideae, with woody capsular fruit and winged seeds, and Melioideae, with 'arillate' seeds or fleshy indehiscent fruits, have been recognized, in some form or other, since 1789. Their rank and circumscription, however, have frequently been debated. Adrien de Jussieu (1830) treated them which could be as families, an opinion Harms, as recently as 1940, suggested justified, though he himself had them as subfamilies, together with a third, based on Cedrela. Apart from the inclusion or otherwise of Cedrela and the related Toona, the Swietenioi- deae has remained a remarkably stable taxon. Only the inclusion orotherwise of the man- has the grove genus Xylocarpus and the related Carapa been seriously disputed; on position of these two genera opinion has been evenly divided. Harms placed them in Melioideae, but the wood Kribs the basis ofwood included them anatomist (1930), on anatomy alone, in Swietenioideae, where he thought Cedrela also belongs. Kribs produced a key to 36 of that each distinct wood If could genera Meliaceae, implying genus is in its anatomy. this be substantiated, xylotemy would indeed be shown to be a powerful taxonomic tool. The based much material than available present study, however, on more was to Kribs, reveals that few distinct their genera are in secondary xylem, though in some cases it provides useful confirmatory characters. In the present study, in which the secondary of evidence which shows that xylem 230 species was examined, convincing is presented Cedrela (and Toona) and Xylocarpus and Carapa have so much in common with the rest of Swietenioideae that their exclusion is unjustified.

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