Monimiaceae

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Monimiaceae

Description

Evergreen shrubs or trees, rarely lianas. Leaves decussate, or rarely in whorls of three, exstipulate, simple, entire or dentate, with spherical oil cells in the lamina, bearing simple or stellate hairs or glabrous. Inflorescence terminal or axil-lary (when in axils of reduced bracts appearing supra-axillary), sometimes cauli-florous, cymose, paniculate, fasciculate or pleiochasial. Flowers unisexual or bisexual, actinomorphic or very rarely (extra-Mal.) oblique, receptacle usually well developed (perigynous), rarely reduced (hypogynous), ± globose or urceo-late to widely campanulate; Fruits of separate drupes or achenes, sometimes plu-mose, frequently enclosed in the persistent receptacle or exposed by various modes of splitting of the receptacle;

Distribution

Africa: present Asia-Tropical:, Malaya (Peninsular Malaysiapresent); New Guineapresent; Thailand (Thailandpresent) Australasia: Indian Ocean: present Nicobar Islands: present Peninsular Thailand: present Polynesia: present SW. Pacific: present Solomon Islands: present South America: present eastern Australia: present warmer parts of the southern hemisphere: present western Malesia: present
About 33 genera with an estimated 320 species, mainly in the warmer parts of the southern hemisphere. There is a concentration of genera in Malesia (11 genera with 86 spp.) with extensions south and east into Australia and the SW. Pacific; further concentrations occur in the islands of the western Indian Ocean and in South America. The family is represented in Africa only by two small aberrant genera and occurs on the Eurasian mainland only in the Malay Peninsula, the Nicobar Islands and Peninsular Thailand.
The Malesian genera are either endemic or nearly so, with one or few species extending to the Solomon Islands (Steganthera) or eastern Australia (Levieria, Palmeria, Steganthera, Kibara and Dryadodaphne). Wilkiea has more species in Australia than in Malesia. Only Kibara extends slightly westwards into the Nicobar Islands and Thailand. The concentration of genera in New Guinea is striking: only Matthaea lies exclusively to the west of New Guinea, the family being represented in western Malesia, otherwise by one species each of Steganthera, Levieria and Palmeria, and by four or five species of Kibara.
The Malesian genera fall within several subfamilies and each of these has a distinctive geograph-ical relationship. Levieria is a member of the tribe Hedycaryeae with relationships in SW. Polynesia; Dryadodaphne falls within the subfamily Atherospermatoideae, a subfamily that is pre-dominantly Australian; while Palmeria is most closely related to Monimia of the Mascarene Is-lands. The remaining genera (Steganthera, Matthaea, Kairoa, Faika, Parakibara, Wilkiea and Ki-bara form a closely knit group within the tribe Mollinedieae which is characteristic of the Malesian region.
Trimenia (Piptocalyx) is referred to the separate family Trimeniaceae.
The ratio of species to genera, in Malesia, is c. 8: 1, but if the largest genus, Kibara, is omitted this reduces to c. 4.3: 1. Five genera are represented by a single species. , .

Dispersal

The fruit-clusters of most Malesian genera consist of few to many drupes, usually black and shining when ripe, sessile or stipitate on receptacles, which are usually enlarged, fleshy and bright yellow and orange. In Palmeria the drupes are exposed when mature by the splitting of the receptacle. They are black or dark reddish brown and are borne on the inner side of the receptacle which is bright red or pink. All these structures are clearly suitable for dispersal by birds or animals, but no records of field observations of this in Malesia are known to me. LORENCE (1980, 1985) records dispersal by birds in Malagasy species of Monimia and Tambourissa which bear fruits of somewhat similar appearance to those of the Malesian genera. In Dryadodaphne fruit structure and means of dispersal are very different, though again this has only been inferred from their structure. The developing achenes are enclosed by the enlarged and indurated receptacle and this splits at maturity to release the ripe achenes. These are dry and spindle-shaped with a persistent aculeate style which becomes markedly plumose. The structure appears well adapted to wind dispersal.

Morphology

Little is known in detail of the shoot morphology of the trees, shrubs and lianas of this family. In Laurelia the bole bears buttresses and the roots develop knee-pneumato-phores. The bark is generally ± smooth with only small fissures and flakes, an exception being Kairoa with prominent corky ridges on the main stems. Throughout the family phyllotaxis is de-cussate or rather rarely with the leaves in whorls of three (e.g. Kibara rigidifolia). Marked ani-sophylly occurs in Glossocalyx. The stems are terete or ± quadrangular, except near the nodes which are somewhat flattened and dilated. The buds, both vegetative and reproductive, are usual-ly enclosed in small scales and there may be more than one in an axil arranged either horizontally or vertically (LORENCE, 1980, 1985), the central bud usually developing first. In spite of the variety of leaf size, form, margin and indumentum, there is a family character which facilitates recogni-tion in the field. This is due, principally, to the venation, which almost invariably is festooned brachidodromous with the secondary veins arising from the midrib at regular intervals and at uni-form angles. An exception noted by LORENCE (1980, 1985) is Ephippiandra. Leaves are usually petiolate but may be amplexicaul (e.g. Kibara ferox). Leaf shape may vary with age. The juvenile leaves of Steganthera hospitans are much narrower than those of adult trees and juvenile speci-mens of Kibara ferox bear narrower and more dentate leaves than do adults. In Kibara ferox, however, the narrow ultimate branches of adult plants bear much narrower leaves than those of the basal parts of the shrub. Heterophylly also occurs in many Tambourissa species and in Hor-tonia.

Inflorescences usually occur in the axils of foliage leaves. When several are grouped among the terminal leaves of a shoot, apparently terminal leafy inflorescences are formed, and with the re-duction of the leaves these may result in large panicles. It is doubtful, however, if the true terminal bud is involved in these inflorescences, the terminal (vegetative) bud aborting. Inflorescences often occur on basal parts of stems where the nodes bear much reduced scales. The upper parts of these stems continue as indeterminate foliage shoots. The presence of multiple buds at nodes which develop in succession allows inflorescences to persist on branches which have lost their fo-liage and to become strikingly cauliflorous. The branching of the inflorescences is cymose, the most simple element being a dichasium. However, several flowers or branches frequently arise from a single node, or alternatively, several pairs of flowers occur along a simple axis (pleiocha-sium — often referred to as racemose). As a result of combinations of these factors individual inflorescences range from solitary flowers, through fascicles of flowers or branches to rather sim-ple cymes and more diffuse and complex paniculate cymes.

Anatomy

General accounts of the vegetative anatomy are given by MONEY, BAILEY & SWAMY (1950) and METCALFE & CHALK (1950). Of particular interest are 1) the universal presence of oil cells (HOBEIN, 1889; PERKINS, 1898), 2) the unilacunar node, with simple strands or arcs of strands entering the petiole, 3) the presence of hippocrepiform sclereids in the pericycle (but not in Siparu-noideae) (MONEY, BAILEY & SWAMY, 1950). Hairs may be simple unicellular, often in fascicles from a common base, or stellate grading into peltate scales. Two-armed hairs have been reported for some genera, including Matthaea.

Phloem plastids. Most members of the Monimiaceae have been found to contain P-type plastids. Very consistently, the Atherospermatoideae have large protein crystals, protein fila-ments and starch (BEHNKE, 1981). Except for the genera Monimia, Palmeria and Tambourissa, the other subfamilies have been found to contain ± small protein crystals besides the dominant starch grains.

Taxonomy

The family as first founded by DE JUSSIEU (1809) included genera representing most of the subfamilies at present recognized. The heterogeneous nature of these genera imme-diately instigated a series of proposals for the division of the family by the recognition of the Athe-rospermataceae or, more recently, into several smaller families. Concurrently other systematists have retained the original broad view of the family. Early proponents of splitting were R. BROWN (1814), BARTLING (1830) and LINDLEY (1853), but the broader view long prevailed among other systematists, principally ENDLICHER (1837), TULASNE (1855), BENTHAM & HOOKER (1880), PAX (1891), PERKINS & GILG (1901), PERKINS (1911, 1925), and MELCHIOR (1964). The more recent pro-posals to remove elements as distinct families include GIBBS (1917), PICHON (1948) and especially MONEY, BAILEY & SWAMY (1950) whose view that Amborella and Trimenia (Piptocalyx) should form separate families has been accepted ever since. The removal of further elements has con-tinued, but opinion remains divided on this trend. A most important contribution by SCHODDE (1969) favoured the recognition of the Atherospermataceae and the same author later proposed the erection of Siparunaceae (SCHODDE, 1970). This was followed by Hortoniaceae (SMITH, 1972). Systematists currently favouring the broader view of the family include THORNE (1974), who brief-ly argues the case for amalgamation concluding 'The logical alternative treatment would be to ex-pect five or more separate and obviously closely related families, an exercise in taxonomic infla-tion that would seem to serve no useful purpose.' The same view is taken by DAHLGREN (1980) and CRONQUIST (1981) and this treatment is adopted here.

Subdivision. The grouping of genera into subfamilies and tribes is still subject to debate. Gener-ally speaking those authors taking a broad view of the family recognize the same subdivisions as the splitters but treat them as subfamilies or tribes. PERKINS (1925) adopted only two subfamilies, Monimioideae and Atherospermoideae with four and two tribes respectively. MELCHIOR (1964) followed MONEY, BAILEY & SWAMY (1950), omitting Amborella and Trimenia, and accepting two subfamilies, Hortonioideae and Siparunoideae. THORNE (1974) added a further subfamily by restricting the Monimioideae to Monimia and Peumus, and forming the Mollinedioideae for the several remaining genera. His reduction of SCHODDE'S subfamily Peumoideae (SCHODDE, 1970) into his restricted Monimioideae is accepted by PHILIPSON (Nordic J. Bot., 1986, in press), who added Palmeria to this subfamily. Most Malesian genera fall into subfamily Mollinedioideae, seven into tribe Mollinedieae and one Levieria into tribe Hedycaryeae. Two other subfamilies are represented by one genus each: Atherospermatoideae by Dryadodaphne and Monimioideae by Palmeria.

Generic limits. The family comprises several small distinctive genera whose definition is not dif-ficult. It is perhaps only among the genera of the tribe Mollinedieae that generic limits become problematic and it is these genera which are abundant in Malesia. In the first place it is possible to distinguish those genera which receive their pollen on a hyperstigma secreted by prominent glands within the ostiole of the female receptacles. These are (in Malesia) Kibara, Wilkiea and Faika. Kibara is distinguished from the other two by the regular arrangement of its stamens. In Wilkiea and Faika the stamens are inserted irregularly over the inner surface of the male receptacles. These two genera are separated by the dehiscence of the anthers: in Wilkiea this is by a single horizontal or horseshoe-shaped slit, whereas in Faika it is by two vertical slits. The two ge-nera are also well separated geographically. Parakibara cannot yet be placed by this system be-cause its female flowers are not known. Three Malesian genera lack a hyperstigma. Of these Ste-ganthera is the largest and is closely related to Matthaea, a genus with a more westerly range, which differs by its anthers opening by two vertical slits. The third genus, Kairoa, is immediately distinguished by the male receptacles which open widely at anthesis to expose the very large num-ber of stamens.

Cytology

The only count known to me based on Malesian specimens is that for Kibara (BORGMAN, 1964). Counts of Australian species of Steganthera and Palmeria, together with a few non-Malesian genera, will be found in the references below. From these counts it is considered that the basic number for the Monimioideae (n= 19) differs from that for the Atherospermato-ideae (n = 22).

Uses

A variety of minor local uses are reported by collectors. The wood of larger species may be used as stakes and for house-building, and the stems of Palmeria spp. for binding. The aromat-ic leaves of several Palmeria species are used for smoking or to provide salt. Meat is wrapped in leaves of Kibara possibly as a tenderizer. Peumus (non-Mal.) has many uses in Chile: the hard wood provides handles for implements and is converted to charcoal, the bark is used for tanning and dyeing, and the leaves for medicinal purposes. Laurelia produces useful timber.

Notes

Species will usually be located by the characteristic foliage or by the conspicuous fruits. As the fruits are not sufficient for generic determination, it is important to search for flowers. These are so inconspicuous that they are commonly dismissed as buds and not collected. If flowers cannot be found on the plant a search in the forest for other specimens will usually prove successful. Always search for examples of flowers of both sexes, and bear in mind that these may occur on separate plants. Examples of the fruits should be preserved in fluid.

Phytochemo

Chemical characters were summarized sixteen years ago (HEGNAUER, 1969). The benzyltetrahydroisoquinoline family of alkaloids (abbreviated: benzylisoquinolines) and essential oils consisting mainly of phenylpropanoids and mono- and sesquiterpenoids were considered to be characteristic secondary metabolites of the family, but the lack of chemical knowledge for Hortonioideae, Monimioideae (except Peumus boldus) and Siparunoideae was stressed. Many members of the family are aluminium accumulators; this character, however, seems to be lacking in Atherospermatoideae. Phenolics were scarcely known, but predominance of the flavonols kaempferol, quercetin and isorhamnetin in leaves, and absence of flavones, flavo-nols with trihydroxylated B-ring and of galli- and ellagitannins had been reported. As a whole phytochemistry of Monimiaceae agreed perfectly with their inclusion in a group loosely termed woody polycarps. In the meantime more became known about the chemistry and distribution of benzylisoquinolines (URZUA & CASSELS, 1978; HEGNAUER, in prep.) and polyphenolic compounds, especially lignans (including neolignans) (HEGNAUER, in prep.). Siparuna gilgiana and S. guyanensis synthesize liriodenine and related oxoaporphine alkaloids, and laurotetanine, N-methyllaurotetanine and leurotitsine were detected in three Palmeria species of New Guinea. The isolated position of Daphnandra with respect to alkaloid metabolism was stressed (URZUA & CASSELS, 1978); only bisbenzyltetrahydroisoquinoline alkaloids, including a number of com-pounds apparently restricted to the genus, have been isolated hitherto from six species. Daphnan-dra aromatica was transferred by SCHODDE to Doryphota; Doryphora aromatica yielded the apor-phine isocorydine besides bisbenzylisoquinolines. Dryadodaphne novoguineense which is con-fined to New Guinea, synthesizes aporphines, oxoaporphines and the bisbenzylisoquinolines dry-adine and dryadodaphnine. 4-Hydroxyaporphines, alkaloids with a very unusual substitution pat-tern were encountered in Laureliopsis philippiana (= Laurelia philippiana). It deserves mentioning that lignans which were known from Trimeniaceae only (Piptocalyx, Trimenia, HEGNAUER, 1969) have been detected in leaves of Laurelia novae-zelandiae; they yielded pinoresinoldimethyl-ether and yangambin. Lignans and many different types of neolignans are widespread in Polycar-picae; they begin to form an outstanding chemical character of the order as a whole. Summar-izing, old and new chemical evidence conforms with the classification of Monimiaceae with woody polycarps without contributing much to the question whether the family is nearer to Mag-noliaceae and Annonaceae or to Lauraceae, i.e., whether inclusion in Laurales is more natural than inclusion in Magnoliales. Chemical evidence also agrees with the exclusion of Amborella-ceae, Austrobaileyaceae and Trimeniaceae which all seem to lack benzylisoquinolines.
— R. HEGNAUER.