Malayan Nature Journal 2012, 64(1), 33-67 The Araceae of Malesia I: Introduction PETER C. BOYCE1* and WONG SIN YENG2 A summary of the aroids of Malesia at the rank of genus and above is offered, covering 44 indigenous genera. Four additional genera (Caladium Vent., Dieffenbachia Schott, Syngonium Schott, and Xanthosoma Schott) are recorded as adventives. The aroid flora of Malesia currently encompasses 1105 indigenous species, with this figure based significantly on understanding of the flora of a few well-studied areas such as Peninsular Malaysia, Jawa , and parts of Malaysian Borneo. Large areas that remain very poorly known include Kalimantan (comprising more than 70% of the land surface area of Borneo), Sumatera, and much of the island of New Guinea. It is estimated that the total will readily exceed 1900 species. General notes on life-forms and taxonomically important morphologies are provided, together with a glossary. A key to Malesian aroid taxa at the rank of genus and above is presented. Keywords. Araceae, Malesia, Indonesia, Malaysia, Philippines, Borneo, Sumatera, Jawa. INTRODUCTION The Araceae is a robustly monophyletic family comprising about 118 genera and approximately 3500 published species (Boyce and Croat, 2011) of herbaceous monocotyledons basal to the rest of the Alismatales (Stevens 2001). The current generic framework is essentially that of Mayo et al., 1997, although since publication there have been significant changes, including the recognition of several new genera in Indomalaya. The most recent molecular phylogenetic analyses of the entire Araceae are Cabrera et al. (2008) and Cusimano et al. (2011). A recent paper also analyses chromosome number evolution (Cusimano et al., 2012). All recent molecular analyses provide good support of much of the internal topography proposed by French et al., (1995) and Mayo et al. (1997). Both also support former Lemnaceae (the duckweeds) to be nested in Araceae and sister to Pothoideae. Acorus, long treated as part of the Araceae, is now unequivocally a separate family Manuscript received: 18 January 2012 Manuscript accepted: 7 February 2012 1 Pusat Pengajian Sains Kajihayat [School of Biological Sciences], Universiti Sains Malaysia 11800 USM, Pulau Pinang, Malaysia. 2 Department of Plant Science & Environmental Ecology, Faculty of Resource Science & Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia. * Corresponding author, email: [email protected] 33 in its own order, and basal to all extant monocots (Grayum 1987, Stevens, 2001). The family is predominantly tropical in distribution, with 90% of genera and about 95% of species restricted to the tropics. The family Araceae is most readily defined by characters of the inflorescence: small flowers borne on a fleshy axis (the spadix) subtended by a modified leaf (the spathe). The sex of the individual flowers and their arrangement on the spadix are among the characters used to define taxonomic groups. The spadix may bear either unisexual or bisexual flowers. If bearing bisexual flowers these are mostly uniformly and densely arranged over the spadix. Bisexual flowers are often subtended by reduced tepals termed a perigon. Unisexual flowers are usually arranged with the pistillate flowers at the base of the spadix and the staminate flowers above, with the zones occasionally separated by a further zone of sterile flowers. In the genus Arisaema individual inflorescences are usually either staminate or pistillate and the sex of the inflorescence is governed by the age of the plant, its health and the type of conditions in which it is growing. Young plants, or mature plants in poor condition or growing in a less than ideal habitat, will produce male inflorescences, while mature plants in good condition growing in an optimum habitat will produce female inflorescences. The ability to alter the sex of the inflorescence in this way is termed paradioecy. Unisexual flowers of aroids are almost without exception naked, that is, lacking a perigon. LIFE-FORMS Aroids for the greater part are plants dependent on abundant available water and prevailing high atmospheric humidity. Since both structurally and physiologically aroids are not well adapted for growth in arid or cold conditions, none are known occur in the most extreme environments, while those that occur in seasonally cold or arid habitats are for the most part geophytes (see below). Araceae are most diverse and abundant in the humid tropics, and it is there that the richest variety of their life forms is found. Indeed, relatively few genera inhabit temperate regions of the world and as noted these are either geophytes (e.g., Arum, Biarum, Dracunculus, Eminium, etc.) or helophytes (e.g., Calla, Lysichiton, Orontium, Symplocarpus, etc.). The Araceae has perhaps the greatest life-form diversity of any flowering plant family with numerous life-form niches having at least one representative species. The most detailed general reviews ecology and life forms are those of Croat (1990, 1992) and Govaerts and Frodin (2003). Using the system Raunkiær (1934) with modifications, primarily from of Schimper (1903) life-forms include climbing or suffruticose primary and secondary hemiepiphytes (e.g., Pothos, most Rhaphidophora, etc.), epiphytes (rare in Asia, but including Remusatia and some Scindapsus), nanophanerophytes (stems persisting for several years; renewal buds above soil level but normally below 3 m – e.g., most Aglaonema, most Apoballis), mesophytic herbaceous phanerophytes (stems herbaceous and persisting for several 34 years; renewal buds above soil level – e.g., most Homalomena, some Apoballis), mesophytic chamerophytes (stems herbaceous and persisting for several years; renewal buds on or just above soil level, and never above 50 cm – e.g., most Schismatoglottis), lithopytes, rheophytes, and chasmophytes (growing in crevices of vertical rock, with vegetative and often reproductive structures pendent) (e.g., many Schismatoglottis, all Piptospatha), hemicryptophytes (stems, herbaceous, often dying back after the growing season, with shoots at soil level surviving; renewal buds just on or below soil level – e.g., Hapaline), geophytes (Amorphophallus), inland (fresh-water – e.g., some Homalomena, Lasia) or estuary (brackish-water, e.g., Aglaodorum) helophytes (hemicryptophytes growing in soil saturated with water or in water with the leaf and flower bearing shoots risinf above water), amphibious or true hydrophytes (e.g., most Cryptocoryne), hydrohemicryptophytes (as for hemicryptophytes, but aquatic – Pistia), and hydrotherophytes (an aquatic therophyte – that is a plant that survived unfavourable seasons as minute restiong buds, or as seeds – Lemnoideae). The least specialized life-form is probably that of mesophytic herbaceous phanerophyte. This is typical of terrestrial herbs from perhumid to everwet and rainforest. Mesophytes are intolerant of atmospheric dryness, dry roots, and direct sun-exposure. They are among the first species to die-out when forests are heavily disturbed. Although mesophytism has been judged primitive in the family by some previous authors (e.g., Grayum, 1990), it is found predominantly in the more ‘advanced’ genera. Typical Malesian mesophytes are Aglaonema, Homalomena, and Schismatoglottis (all subfamily Aroideae). Among so-called ‘primitive’ groups only tribe Spathiphylleae (Spathiphyllum and Holochlamys), and some terrestrial Anthurium species, have this lifeform. Amphibious or true hydrophytes, hydrohemicryptophytes (e.g., Pistia), and hydrotherophytes (Lemnoideae), are scattered throughout the family from very primitive groups (e.g., subfamily Orontioideae) and the Lemnoideae, to very advanced ones such as tribe Cryptocoryneae and Pistia (Aroideae). Within subfamily Lasioideae, Lasia, Podolasia, and many species of Cyrtosperma, have life-forms that appear intermediate between helophytic/mesophytic and geophytic/mesophytic. Predominantly African (but with one species in N Borneo) Nephthytis Schott, in which the rhizomes normally grow superficially, has a considerably more mesophytic habit than the strongly tuberous stemmed Anchomanes Schott and Pseudohydrosme Engl., the other two genera of tribe Nephthytideae. African Culcasia has many terrestrial species, spanning the hemiepiphytic/mesophytic categories, and Philodendron is similar. Anubias is predominantly helophytic but Dieffenbachia and Spathiphyllum, while typical of wetter habitats, also occur on drier ground within a humid tropical habitat. Hemiepiphytes are commonest in the more primitive tribes and subfamilies. Most genera of subfamilies Pothoideae and Monsteroideae are hemiepiphytes and among more advanced genera this life form occurs only in African tribe Culcasieae, Philodendron, and Syngonium, all belonging to subfamily Aroideae. These genera show marked structural adaptations in their habit and in these features must be considered derived. 35 In the predominantly geophytic tribes Caladieae and Colocasieae, Alocasia, Colocasia and Xanthosoma each contain mesophytic species with decumbent to erect, arborescent stems; Steudnera and Chlorospatha are exclusively of this type. The most primitive Araceae, subfamilies Gymnostachydoideae and Orontioideae, are geophytes, rhizomatous helophytes or aquatics, and largely extra-tropical. While their habits are doubtless a prerequisite for survival in a more demanding climate, and therefore could have evolved from a mesophytic common ancestor, it is nevertheless equally possible that the mesophytic habit has evolved various times within the more advanced subfamilies from geophytic or helophytic ancestors. The geophytic habit is strongly represented in the relatively primitive subfamily Lasioideae and particularly common in the most advanced subfamily Aroideae. The rheophytic habit is characteristic of tribe Schismatoglottideae, the genera being almost exclusively rheophytic except for Schismatoglottis, which consists mainly of terrestrial mesophytic herbs. Hemiepiphytes Humid tropical forests are the characteristic habitat of hemiepiphytic genera. The species vary considerably in size, from shortly climbing plants found on the major branches or trunks of trees to huge plants with attached stems growing high into the forest canopy and producing enormously long, pendent flowering stems (e.g., Scindapsus pictus. Hemiepiphytes can be divided into primary and secondary hemiepiphytes. Primary hemiepiphytes begin growth above ground level but produce feeder roots which eventually grow down to the forest floor. Secondary hemiepiphytes germinate on the forest floor, grow up tree boles, become detached from the ground by rotting of the juvenile stem but then become reconnected later by feeder roots which grow down from the upper internodes. Hemiepiphytic aroids typically have anchor roots as well, and are thus often called ‘root climbers’. Flagelliform shoots, heteroblastic leaf development and shingle plants are characteristic features of hemiepiphytic Araceae, though not present in all species of each genus. Highly developed heteroblasty coupled with skototropism, a specific growth strategy for seeking host tree boles, has been described in Monstera (Madison 1977, Strong and Ray 1975) and occurs in all climbing aroids in Malesia. In certain species the seedling is a very slender, plant with long internodes and minute scale leaves. Having germinated on the forest floor it seeks the defined area of shadow represented by the nearest tree bole. Once the tree has been reached the plant transforms itself into the shingle form and later, higher up, into a mature flowering plant. Vegetative reproduction may then take place by the production of flagelliform shoots. Seed size is almost certainly an important element in the growth strategies adopted by hemiepiphytes. The mature flowering region of the stem is short with abbreviated internodes and more-or-less rosulate foliage leaves. The continuation shoot climbs upwards and is slender and flagelliform with cataphylls instead of foliage leaves. After an interval it produces another rosulate-leaved mature zone. The repetition of this pattern produces a series of connected rosulate plants 36 one above the other on a single tree trunk. Epiphytes True epiphytes, which never become connected to the ground by feeder roots, are found in Anthurium, Arophyton, Philodendron, Remusatia, Scindapsus and Stenospermation. The seeds presumably germinate directly on the host tree after dispersal by birds or other animals. Many species of Anthurium sect. Pachyneurium, some Philodendron, and some species of Scindapsus are litter-basket epiphytes. The large leaves form an inverted cone in which leaf litter and other debris accumulate and into which the roots grow and ramify in a dense mass. Remusatia vivipara, which has a tuberous stem, is a widespread epiphyte, owing to the dispersal of hooked bulbils which are probably transported by birds and primates high in the forest canopy. Lithophytes Many hemiepiphytes, epiphytes and geophytes are also found as lithophytes in suitable conditions. Lianescent hemiepiphytes frequently grow on rocks in forest regions wherever shade and humidity are sufficient, the rock surface providing much the same conditions for attachment as tree boles. A number of geophytes are characteristically found growing in the eroded, litter or humus-filled cavities of limestone outcrops; examples are numerous Amorphophallus, and Typhonium species in S.E. Asia. Rheophytes are also typically lithophytic. Geophytes This category includes all genera with tuberous, rhizomatous, subterranean or partly subterranean stems. Geophytic aroids characteristically have periodic dormant periods when no leaves are present and these normally correspond to the dry season (or winter) of their habitat. However, rainforest geophytes exhibit growth periodicity and dormancy even in non-seasonal climates, e.g., Amorphophallus and Typhonium. Several genera occur in more than one kind of climatic regime. The genera Amorphophallus and Dracontium are similarly diverse ecologically, with species in rainforest or in seasonal evergreen forest, deciduous forest, savannas or grasslands. Strongly seasonal grassland species flower without the leaves at the end of the dry season, mostly after the first rains fall. Leaf and fruit development take place during the rainy season. Rheophytes Rheophytes (sensu van Steenis 1981, 1987) are flood-resistant plants, usually of tropical rainforests, growing in or along swift-running streams or rivers up to the flood level. They are characterized by narrow, leathery leaves and a firmly attached, usually epilithic stem. In addition to tribe Schismatoglottideae, in which the majority of genera have this habit, rheophytes are also found in Homalomena, Anubias and Holochlamys, and rarely in Anthurium and Spathiphyllum. 37 Submerged or periodically submerged aquatics Many Cryptocoryne species are permanently submerged plants, either aquatic (permanently in water) or amphibious (subjected to seasonal drying-out of the habitat, often accompanied by plant dormancy). Either the inflorescence as a whole or its upper portion is held above the water surface while all other parts are completely submerged. Cryptocoryne is the largest genus of aquatic aroids and merits more detailed consideration. There are a number of species which are usually submerged but which are emergent at times of exceptionally low water (e.g., C. affinis). The submerged leaves of such species are relatively large, whereas the emergent leaves are quite small, indicating that such conditions are unfavourable to their growth. The submerged and emergent leaves of the same species generally look very different in shape, size, colour and structure. Submerged leaves are softer and emergent ones more coriaceous. Many species occur in the freshwater tidal zone where there is a daily cycle of exposure and submersion. Some species are found only in freshwater, like C. affinis, and C. cordata, while others can grow both in fresh and brackish water (C. ciliata). A few species are helophytes, preferring swampy conditions and growing during the dry season completely emergent in normal soil, like C. spiralis, a weed of rice fields in India. Usually Cryptocoryne species flower at low water level when the plants become emergent. Helophytes Helophytes are widespread throughout the family in many different taxonomic groups in both temperate and tropical genera. There is little constancy in habit type. The stem may by tuberous (e.g., Caladium, Typhonium), rhizomatous (Homalomena rostrata), rhizomatous and arborescent (Montrichardia), semi- prostrate to aerial (Lasia), erect and arborescent (Philodendron) or merely shortly erect and aerial (Homalomena). The helophytic life form may be considered relatively unspecialized in the majority of genera which exhibit it. Tuberous or rhizomatous stems may be associated with seasonally flooded habitats and a marked dry season. Rhizomes may, on the other hand, be adaptations for colonizing muddy riverine margins as in the case of the strict helophytes Typhonodorum and Montrichardia. Genera such as Dieffenbachia, Homalomena and Spathiphyllum generally exhibit no special adaptations in their helophytic species, which appear to take advantage of wetter habitats for more vigorous growth rather than because of a strict requirement for a flooded substrate. Free-floating aquatics The only free-floating species of Araceae are the pantropical Pistia stratiotes and the five genera of the Lemnoideae (former Lemnaceae – the duckweeds), four of which are native to Malesia. 38 INFLORESCENCES The inflorescence of Araceae is composed of an unbranched spike bearing flowers, the spadix, subtended by a bract termed the spathe. Flowers are usually numerous, mostly small, sessile in most genera (exceptions include Arisaema, Arisarum, and Pedicellarum), and always lack floral bracts. Flowers are generally spirally arranged and usually tightly packed, although in some species of Pothos, Pedicellarum, Amorphophallus (staminate and pistillate flowers), tribe Spathicarpeae (pistillate flowers), and many species of Arisaema and Arisarum (staminate flowers), they may be somewhat distant from one another. The spathe is, strictly speaking, the last leaf of a flowering article [module]. It is often a specialized attractive organ, although in some genera (e.g., Gymnostachys, Orontium, Pothos, etc.) it is inconspicuous. The internode between spathe and spadix (the spadix stipe) is usually short or absent, while the peduncle – the internode between spathe and last foliage leaf or cataphyll – is usually much longer. However, in some basal taxa this arrangement is reversed (e.g., Gymnostachys, Orontioideae, some Pothos species, etc.). The typical aroid inflorescence pattern has given rise to a wide range of morphological ‘forms’ in the different genera, which appear to represent an evolutionary trend of increasing integration towards a synflorescence. Spathe and spadix modifications are often closely related so that the spathe may be seen evolutionarily as becoming increasingly integrated into the inflorescence itself, until in extreme cases, such as Cryptocoryneae, and the genera Ambrosina, Pistia and Pinellia, fusion and still more elaborate modifications have brought about division of the spathe into separate chambers. Other notable specializations of the inflorescence include the wide range of odours found in different genera, colour patterns, especially on the spathe, and the relative persistence of different regions of the spathe. In Homalomena and Philodendron, for example, the entire spathe persists until fruit, while in most genera of tribes Colocasieae, Caladieae, Peltandreae and Schismatoglottideae the spathe limb withers or falls during or very soon after anthesis while the lower spathe persists into fruiting. In many Monstereae the entire spathe withers or falls soon after flowering, a behaviour which is correlated in this tribe with the presence of numerous protective trichosclereids in the style tissue. Terminal appendices of the spadix occur in tribes Areae, Arisaemateae, Colocasieae, Schismatoglottideae, Thomsonieae and Zomicarpeae, sporadically elsewhere in the family. The function of the appendix, where it has been investigated, is to produce odours to attract pollinators (osmophore, Vogel 1963, 1990). The appendix is either clearly composed of staminodes (e.g. some Amorphophallus) or partially to entirely smooth with no vestiges of floral organs (e.g., Typhonium). Flowers in Araceae may be 2- or 3-merous. In perigoniate flowers the tepals, when free, are organized in two whorls. The tepals are usually more-or-less fleshy and fornicate apically. In some taxa (Anadendrum, Holochlamys, Pedicellarum, Spathiphyllum sect. Massowia, and Stylochaeton) the tepals are fused into a cup- like structure. Stamens in perigoniate flowers and in naked bisexual flowers of 39 most Monsteroideae have distinct (usually flattened) filaments, basifixed anthers and a slender, inconspicuous connective. In the unisexual flowers of many tribes of subfamily Aroideae, however, filaments are typically very short or effectively lacking, and there is a thick, fleshy connective which probably acts as an osmophore (Aglaonemateae, Culcasieae, Homalomeneae, Montrichardieae, Nephthytideae, Philodendreae, and Zantedeschieae). Stamens of tribes Anubiadeae, Caladieae, Colocasieae, Peltandreae, and Spathicarpeae are essentially similar but are always fused into synandria. In tribe Arophyteae the stamens may be fused or not and exhibit a diversity of structure. Large connectives also occur in tribe Spathicarpeae but their different morphology suggests that they are not homologous with those of the other tribes of subfamily Aroideae mentioned above. Anthers are almost always extrorse (introrse in Zamioculcas, latrorse in Pedicellarum). Theca dehiscence may be by a longitudinal or rarely transverse slit (most genera with bisexual flowers and some unisexual-flowered genera: Anubias, some Areae, Arisaema, Arisarum, and Stylochaeton) or by apical or subapical pores, or short slits. In many genera of subfamily Aroideae dehiscence of each theca is by a subapical stomial pore and this morphology is frequently correlated with the extrusion of pollen in strands. The gynoecium usually varies between 1- and 3locular, and when unilocular often shows traces of 2- or 3-merous origin through the presence of a several lobed stigma (e.g., Typhonodorum), or more than one placenta (e.g., Schismatoglottis). Gynoecia with more than 3 locules are less common, but occur in tribe Spathicarpeae (1–8 locular), and in Philodendron (2–47 locular). Placentation varies from axile to parietal, basal, apical or basal and apical (the latter in Dracunculus, Helicodiceros, some Aridarum, and Theriophonum), with many intermediates. Ovules may be anatropous, campylotropous, orthotropous or intermediate between these types. Funicle trichomes are usually present (French 1987) and secrete a clear, mucilaginous substance which in many genera (e.g. tribe Monstereae, Philodendron) entirely fills the ovary locules; this secretion appears to play a role in pollen tube growth (Buzgó 1994). The style may be narrowed and elongated (e.g., Dracontium and some Philodendron) but in most genera is relatively inconspicuous externally. However, there is very often a thick stylar region between the ovary locules and stigma (e.g. Philodendron, Mayo 1989b). In tribe Monstereae this stylar region is especially well developed and densely filled with trichosclereids. Here the style seems to substitute functionally for a perianth in protecting the sexual organs of the flower. Stigmas are always wet in Araceae and in some genera (Anthurium, Arum, and several Lasioideae) produce conspicuous nectar droplets at anthesis. In Amorphophallus, Dieffenbachia and some Spathicarpeae, the lobing of the stigma can be very pronounced, or the stigma relatively massive. In subfamily Monsteroideae stigmas vary from subcapitate to conspicuously elongated, either transversely (e.g. Anadendrum) or longitudinally. Infructescences Fruits of Araceae are typically juicy berries, very rarely dry and/or leathery. The 40 berries are almost always free. Exceptions are Syngonium, in which the berries form an indehiscent syncarp, Cryptocoryne which has an apically-dehiscent syncarp, and Lagenandra in which the syncarpels open actively at the base to release the seeds. In the most Monstereae, the thick stylar region of the bisexual flower is shed to reveal the seeds. The stylar region is filled with trichosclereids which are thought to protect the developing seeds. In perigoniate genera such most Lasioideae, and Anthurium, the perigone seems to plays a protective role and keeps pace during growth of the developing berry, with the latter only becoming fully exposed at maturity by extrusion from the flower. In Anthurium the berries are held at the level of the tepals by slender filaments torn from the inner epidermis of the tepals. In Lysichiton, also perigoniate, the stylar region and tepal apices protect the young berry, eventually breaking off to reveal the ripe seeds (Hultén and St. John 1931). In many unisexual-flowered genera a protective function is assumed by the persistent spathe or lower spathe. Spathe growth continues around the developing fruits until maturity when the spathe may split open (Alocasia, Dieffenbachia) or absciss at the base (Philodendron), exposing the infructescence of white or coloured berries. In other monoecious genera, however, the spathe is marcescent and plays no role in fruit protection. In such cases (e.g., Arisaema) protection may possibly be through the presence of toxic chemical compounds in the berries. WEB RESOURCES The following websites provide excellent and more importantly scientifically accurate information for the Araceae: The International Aroid Society website: http://www.aroid.org/ Creating a Taxonomic e-Science – Araceae: http://www.cate-araceae.org/ Tropicos: http://www.tropicos.org/ International Plant Names Index: http://www.ipni.org/ World Checklist of Selected Plant Families (a constantly updated list of published plant names): http://apps.kew.org/wcsp/ The Crypts Pages (site dedicated to Cryptocoryne and Lagenandra): http:// crypts.home.xs4all.nl/Cryptocoryne/index.html Cryptocory.net (in Japanese but excellent images with scientific names: http:// cryptolove.jimdo.com/ David Scherberich: http://www.aroidpictures.fr/ Bulletin of Russian Anubias forum: http://anubias-engl.blogspot.com/ Lemnoideae (duckweeds): http://waynesword.palomar.edu/1wayindx.htm 41 TAXONOMIC TREATMENT Araceae Juss., Gen. Pl.: 23 (1789) (‘Aroideae’), nom. cons. Type genus: Arum L. Lemnaceae Martynov, Tekhno-Bot. Slovar: 362. (1820) (‘Lemnoides’), nom. cons.; Lemnaceae Gray, Nat. Arr. Brit. Pl. 2: 729. (1822), nom. cons. Type genus: Lemna L. Pistiaceae Rich. ex C.Agardh, Aphor. Bot.: 130. (1822). Type genus: Pistia L. Callaceae Rchb. ex Bartl., Ord. Nat. Pl.: 25, 66. (1830). Type genus: Calla L. Orontiaceae Bartl., Ord. Nat. Pl.: 24, 68. (1830). Type genus: Orontium L. Arisaraceae Raf., Fl. Tellur. 4: 16. (1838). Type genus: Arisarum Mill. Pothaceae Raf., Fl. Tellur. 4: 16. (1838). Type genus: Pothos L. Cryptocorynaceae J.Agardh, Theoria Syst. Pl.: 32. (1858). Type genus: Cryptocoryne Fischer ex Wydler Dracontiaceae Salisb., Gen. Pl.: 7. (1866). Type genus: Dracontium L. Caladiaceae Salisb., Gen. Pl.: 5. (1866). Type genus: Caladium Vent. Philodendraceae Vines, Stud. Text-book Bot. 2: 540. (1895). Type genus: Philodendron Schott Monsteraceae Vines, Stud. Text-book Bot. 2: 540. (1895). Type genus: Monstera Adans. Colocasiaceae Vines, Stud. Text-book Bot. 2: 541. (1895). Type genus: Colocasia Schott Wolffiaceae Bubani, Fl. Pyren. 4: 22. (1902). Type genus: Wolffia Horkel ex Schleid. 42