4 AROIDEANA, Vol. 11, No.3

Ecology and Life Forms of Araceae Thomas B. Croat Missouri Botanical Garden RO.Box299 st. Louis, Missouri 63166-0299

INTRODUCTION casts a darker shadow) where a physio­ Araceae, a family of herbaceous mono­ logical change takes place allowing them cotyledons with 106 genera, is a com­ to grow toward light (Strong & Ray, plex group in terms of life form and 1975). They grow as appressed epi­ ecology. The family is widespread, with phytes on trees or as vines in the canopy. almost an equal number of genera in Others begin their lives as true epi­ both the Old and New Worlds, but with phytes, some reconverting to hemiepi­ the majority of species occurring in the phytes by producing long, dangling roots New World tropics. A few genera range contacting the forest floor below. into north temperate regions with one species ranging to at least 63 degrees Some species, especially members of north latitude. Few aroids range into subfamily Monsteroideae, have heterob­ temperate regions of the southern hemi­ lastic development with leaf and stem sphere; the most southernly being Pistia morphology reflecting the differences in stratiotes L., which can be found through their growth phases. Juvenile plants may 36 degrees south latitude in Argentina. produce a small terrestrial rosette of The family occupies a wide variety of life leaves, then grow rapidly, producing a zones and habitats throughout its range, few small leaves on long internodes. The extending from tropical dry to pluvial preadult leaves of the first hemiepiphytic rainforest, but also ranges into subarctic phase of such plants are often very marshes, tropical swamps, cloud forests, distinct from the adult leaves. Many such cold windswept montane plains and species are able to convert again and semi-arid to arid coastal plains. The again from adult growth (consisting of family has many species which will not short, thick internodes) back to juvenile tolerate any degree of frost or cold such growth (with elongate internodes bear­ as Anthurium brownei Masters, as well ing smaller leaves), either to establish as some, like Symplocarpus foetidus (L.) more adult plants with a rosette of leaves Nutt., which actually emerge from snow­ or to survive the dynamics of an ever­ covered ground. changing forest, complete with treefalls The most interesting aspect of the and falling branches (Ray, 1987). Other family's ecology is the diversity of adap­ hemiepiphytic species are vines which tive life forms. These range from sub­ branch and produce growth throughout merged to free-floating, and emergent the lower and middle levels of the aquatics to terrestrial plants and to canopy. These species (e.g., Philoden­ epilithic or epiphytic forms which may dron scandens K Koch & Sellow) ac­ be true epiphytes or hemiepiphytic complish long-term survival by having a (growing on trees but rooted in soil). portion of their biomass in a part of the Hemiepiphytism is diverse itself, with canopy which survives any particular some species beginning their lives as treefall (Pefialosa, 1975). Even true epi­ terrestrial seedlings, then growing phytes rarely succumb promptly to a fall skototropically (toward darkness) until from their host tree, but instead con­ they arrive at the nearest suitable tree tinue to flower and fruit on the ground ( usually a relatively large one which for a limited time. T. Croat, 1988 5

DISCUSSION by only one genus, with one pantropic The following is an outline and discus­ and variable species. Pistia stratiotes L. sion of life form diversity in the Araceae has a short stem and a rosette of (see Appendix III for a glossary of aerenchymatous, buoyant leaves, with a terms): cluster of fine, hair-like roots below. It 1. Aquatic plants occurs mainly at lower elevations and 1.1 Submerged aquatics inhabits mostly open, fresh waters at the 1.2 Free-floating aquatics edges of slow-moving streams, lakes and 1.3 Emergent aquatics ponds. This species is remarkably suc­ 2. Terrestrial plants cessful in using mostly vegetative repro­ 3. Epilithic plants duction, often totally clogging small to 4. Epiphytic plants large waterways in a short period of 4.1 Hemiepiphytes time. Vines Appressed climbers 1.3 Emergent Aquatics 4.2 Epiphytes Emergent aquatiCS make up a very large group within Araceae. Many genera 1.1 Submerged Aquatics have at least some species which spend Jasarum steyermarkii Bunting has per­ all or part of their lives rooted in manently submerged leaves and is the standing or moving water. Temperate only true example of this life form North America is particularly rich in among neotropical Araceae. It grows aquatiC or semiaquatic genera. Most, rooted in moving streams on the escarp­ including Acorus, Calla, Lysichiton, ment of the Guayana Highland where it Orontium, Peltandra and Symplocar­ is endemic (Bogner, 1985). When it pus, grow in swampy or marshy areas, flowers, the scape is protruded above lakes, ponds, or along the edges of the level of the water. Many rheophytes, creeks. Arisaema triphyllum (L.) Torr. however, may spend a portion of their is also reported as sometimes occurring lives underwater with no apparent harm, in swampy areas (Small, 1933; Correll & but flowering occurs when the plants are Correll, 1972). mostly emerged and have only their Some emergent aquatics, e.g., Mon­ short stems below water. Species of trichardia arborescens (L.) Schott, Pel­ Acorus, Anubias, Lagenandra, Spa­ tandra virginica (L.) Kunth, Cryptoco­ thiphyllum and especially Cryptocoryne ryne ciliata (Roxb.) Fischer ex. Schott are used as aquarium plants and may be (D. Nicolson, pers. comm.) and Typhon­ submerged completely for indefinite pe­ odorum lindleyanum Schott O. Bogner, riods of time without apparent injury. pers. comm.), occur in tidal zones. Even Dieffenbachia has been used in While most emergent aquatiC genera aquaria (D. Nicolson, pers. comm.) in the neotropics are well-rooted, terres­ The Asian tropics, in contrast to the trial plants, some are epilithic, such as a American tropics, have large numbers of rheophytic group of Anthurium (A. submerged aquatics, the most important andicola Liebm., A. sytsmae Croat, A. being the genus Cryptocoryne. Members rupicola Croat and A. antioquiense of this genus spend most of their lives in Engl.) and SpathiphyUum (S. quin­ shallow water, but typically flower at diuense Engl.), although the percentage periods of low water (when their leaves of rheophytic species for each genus is have emerged above water level) or low. when the water level is low Oacobson, The Asian tropics, on the other hand, 1980, 1982;). Bogner, pers. comm.). are much richer in rheophytic plants. Aridarum, Bucephalandra, Cryptoco­ 1.2 Free-floating Aquatics ryne, Furtadoa, Heteroaridarum, Hotta­ Free-floating aquatics are represented rum, Lagenandra, Phymatarum, Pipto- 6 AROIDEANA, Vol. 11, No.3

spatha, some Homalomena and some considered aquatiC in the true sense. Schismatoglottis, have the majority, or Many are, in fact, principally epiphytic all, of their species occurring along or in genera which find steep, well-drained streams, frequently clinging to rocks on stream banks good substitutes for the stream banks (van Steenis, 1981). normal epiphytic habit (see below). The majority of emergent aquatic plants are not rheophytic, but rather 2. Terrestrial Plants occur in flowing or standing water. The terrestrial habit is predominant Among the New World genera, which for aroids on a world-wide basis. Terres­ are nearly always found growing in trial genera are the most diverse ecologi­ water, are Dracontioides, Montrichar­ cally, occurring in humid to very dry dia and Urospatha. Other genera, such as habitats, in secluded forest understory Diejjenbachia, Philodendron and Spa­ and in open, exposed areas. While most thiphyllum have some species growing genera comprise mainly understory in aquatic or marshy situations. An­ plants in primary forest, some range into aphyllopsis (A. Hay, 1989) grows along savannas, exposed steppes, alpine mead­ streams or in swampy areas in the ows and even into semidesert areas. understory and survives partly underwa­ Terrestrial aroids range in habit from ter part of the year. Homalomena some­ caulescent plants (Diejjenbachia and times occurs in varzea forest in the Aglaonema) to tuberous plants (Amor­ Amazon basin, and survives underwater phophallus, Arum and Dracontium), to conditions for long periods, then toler­ rhizomatous (rarely also reported as ates swampy situations until the water cormose - see Colocasia, Therio­ fully recedes. phonum or 1jIphonium in Appendix II.) In addition to the rheophytic genera and to subscandent plants ( Cercestis and mentioned above, there are a number of Culcasia). other, chiefly emergent aquatics in Asia A large percentage of terrestrial aroids usually growing along streams or in have rhizomes, or short stems with short swamps. They differ in that they are not internodes, which usually creep over the usually clinging to rocks or to steep surface of the soil or just beneath the soil banks, but are rooted along the edges of surface. Rhizomes may be deeply rooted, water courses and usually have subterra­ as in Cyrtosperma and Spathiphyllum, nean root systems. These include most but most are weakly or loosely rooted. A species of Cryptocoryne, Cyrtosperma, few species of Anthurium (e.g., A. as well as Anubias, Aglaodorum (in ochranthum K Koch, A. pluricostatum brackish water), Lagenandra, Lasia and Croat & Baker) and Philodendron (e.g., Podolasia. P. grandipes K Krause) are deeply Africa, a generally much drier conti­ rooted terrestrial plants, although these nent than Asia or America, has relatively genera are typically epiphytic. fewer exclusively aquatiC genera, al­ Most of the rhizomatous creeping though Anubias has species which are genera, as well as caulescent plants like principally aquatic. Lasimorpha sene­ Dieffenbachia and Aglaonema, have the galensis Schott from tropical West Africa apical portion of their stems erect with is also an emergent aquatic. In Madagas­ the older part reclining. Typically, when car (also introduced in surrounding a plant reaches a certain height, the islands), 1jIphonodorum is almost al­ weight of the added growth causes the ways found in standing water. lower part of the stem to recline. As a Many other genera, in both the Old result, older plants of Diejjenbachia, and New Worlds, frequently grow on Xanthosoma and terrestrial Rhodospa­ stream banks but rarely come in direct tha may have stems extending for more contact with the water and cannot be than a meter over the forest floor. T. Croat, 1988 7

Paleotropical terrestrial aroids are identical to the conditions an epiphyte often direct ecological and growth form encounters while growing on tree counterparts of neotropical genera with­ trunks. The distinction between an epi­ out necessarily being phylogenetically phyte and an epilithic plant is often related. For example, Amorphophallus blurred as well (see below). (Aroideae) and Anchomanes (Philoden­ In the neotropics, there is a total of 22 droideae) of the paleotropics look super­ strictly terrestrial genera with 267 ter­ ficially like Dracontium (Lasioideae) of restrial species (including emergent the neotropics and behave in the same aquatics), with perhaps an additional manner, Le., an inflorescence being pro­ 250 species in the genera Anthurium, duced before the single large leaf is Philodendron and Rhodospatha (genera produced. which are largely epiphytic). The major­ Among the temperate North Ameri­ ity are inhabitants of the humid, warm, can genera, all except Arisaema, are tropical areas, which contribute 14 gen­ associated with the aquatic habitat, era and almost 500 species. Ten addi­ though most, including Acorus, Calla, tional genera with 25 species occur Lysichiton, Peltandra and Symplocar­ principally in cooler or drier habitats in pus may sometimes be found on dry land mostly subtropical or temperate South but rarely far from water. Orontium is America, while temperate North Amer­ always aquatic. Even some species of ica contributes an additional six genera Arisaema (A. dracontium (L.) Schott) and 13 species (see Appendix I for the are most frequent in swamp forest and estimated number of terrestrial species riparian habitats (M. Grayum, pers. in each group). comm.). Many of the genera, especially in the Most neotropical terrestrial species southern part of the neotropics, are are understory plants occurring in better adapted to growing in harsher humid to wet primary forest, at the edges conditions. Because of the latitudes or of primary forests or in open areas in elevations at which they occur, they are forests, or along stream banks. The adapted to relatively extreme conditions genera involved are Anaphyllopsis, Ca­ of drought or cold. These genera include ladium, Chlorospatha, DiejJenbachia, Asterostigma, Gorgonidium, Mango­ Dracontium, Pilarum, Spathiphyllum, nia, Scaphispatha, Spathantheum, Spa­ Ulearum, Xanthosoma and Zomicarpa thicarpa, Synandrospadix and Tac­ as well as some species of Anthurium, carum, as well as some species of Philodendron, Rhodospatha and Steno­ Xanthosoma. All are tuberous, and most spermation. The habit of Zomicarpella have an interrupted growth period due is also that of an understory herb. A few to conditions of cold (as is the case of other genera, including Stenosperma­ those in Argentina or at high elevations tion, may occur on steep banks, where in the Andes) or to drought, when leaves drainage is good and the ecological are deciduous. While some genera usu­ situation closely matches the epiphytic ally occur as understory plants, (Asteros­ habit, but this is commonly true only in tigma, Spathantheum, Spathicarpa and areas of disturbance, such as along some species of Taccarum), other gen­ eroding river banks and roadcuts. era frequently occur in more open At higher elevations on steep slopes, habitat (Mangonia, Gorgonidium, and especially in cloud forests, the Scaphispatha, Synandrospadix and distinction between the epiphytic and some species of Taccarum and Xantho­ terrestrial habit may break down alto­ soma). gether. The general accumulation of A higher percentage of paleotropical, debris on the forest floor and good as opposed to neotropical, genera are drainage makes such situations virtually terrestrial and are more ecologically 8 AROIDEANA, Vol. 11, No.3 diverse. Most of the endemic African Australia has seven indigenous terres­ genera are terrestrial in habit. On main­ trial genera, each with only one or two land Africa these include Ancbomanes, species. These are Alocasia, Amor­ Anubias, Callopsis, Gonatopus, Nepb­ PboPballus, Colocasia, Gymnostacbys, tbytis, Pseudobydrosme, Stylocbaeton, Remusatia (also epiphytic), Sauroma­ Zamioculcas and Zantedescbia, as well tum and Typbonium. Only Gym­ as some species of Cercestis and Culca­ nostacbys is endemic at the generic level sia. In the Malagasy area, terrestrial (Amorpbopballus, Alocasia and 1Y­ genera include Aropbyton, Carlepbyton, Pbonium have endemic species). Aside Colletogyne and Protarum (Seychelles). from the terrestrial species, there is one As in the neotropics, most of the species aquatic (Pistia), one epiphytic (Re­ in these genera occur in the understory musatia vivipara (Roxb.) Schott) and of primary, mostly humid forests. In­ six hemiepiphytic species, so that sixty deed, with the exception of a few species percent of the araceous flora is terres­ of two genera, Potbos and Rbapbido­ trial. pbora, most of which occur in Asia, all of Ecologically, the Asian terrestrial spe­ the African genera are basically terres­ cies are more complex than those in trial. The genus Anubias has some spe­ Africa. As is the case in the American cies which are aquatic at least part of the tropics, the majority of the terrestrial time, and both Cercestis and Culcasia species are understory plants occurring have species which are hemiepiphytic. in humid primary forests, but a higher A high percentage of the endemic percentage of Asian genera occur in African genera are adapted to a dry marshy areas. The greatest concentra­ season and have developed tuberous tion of genera is in the Malesian region, stems or rhizomes. These include An­ mostly in evergreen forests, but large cbomanes, Aropbyton, Carlepbyton, numbers of species also occur in mon­ Colletogyne, Gonatopus, Protarum and soon forests further to the north, with a Remusatia. In addition, all of the north respectable number of species ranging as African genera of Mediterranean climate far north as China and Japan. Asian areas (see below) are tuberous, as are understory genera include Aglaonema, the three genera which also occur in Alocasia, Amorpbopballus, An­ Asia, namely Amorpbopballus, Sauro­ apbyllum, Arisaema, Colocasia, Crypto­ matum and 1Ypbonium (the last natural­ coryne (usually in dried out pools and ized in Africa). Stylocbaeton, though not also included under "rooted aquatics"), tuberous, accomplishes the same ability Cyrtosperma, Hapaline (usually terres­ to survive long periods of drought by trial, rarely epiphytic), Holocblamys, having a short rootstock with thick Homalomena, Remusatia (also in­ succulent underground roots. cluded among "hemiepiphytes"), Not surprisingly, all species occurring Sauromatum, Scbismatoglottis, Spatb­ in Europe and in the Mediterranean ipbyllum, Steudnera and 1Ypbonium. region are terrestrial and most (except Pycnospatba is also an understory herb. Arisarum, Calla and the introduced The majority of the terrestrial Asian Acorus, which are rhizomatous) are genera have rhizomatous stems, though always tuberous. Most species of Arum some (Amorpbopballus and Pycnospa­ are adapted to dormancy during the tba) have tuberous stems and are northern winters or during the hot, dry adapted to short to relatively long peri­ Mediterranean summers. The tuberous ods of dormancy. Most Asian species of genera include Ambrosina, Arum, Bia­ AmorPboPballus occur in closed pri­ rum, Dracunculus, Eminium and Heli­ mary or secondary forest undergrowth codiceros. See Appendix II for ecological (van Alderwerelt van Rosenburgh, 1920, requirements of these genera. Hu, 1968, Johns & Hay, 1981), but T. Croat, 1988 9 sometimes also in open areas (see Ap­ Hook. f., Typhonium albispathum pendix II). Bogner and Amorphophallus putii Gag­ While some terrestrial aroids have nepain), but more commonly, species relatively long, erect stems, the majority occur both on the limestone and on the have short internodes and are tuberous trees growing over and in between or rhizomatous. A few genera are re­ limestone rocks. In the neotropics, as ported as cormose and there are differ­ well as in Asia, craggy limestone areas ences of opinion as to whether they are are invariably good aroid sites, and tuberous or cormose (see Colocasia, depending on the amount of rainfall in Theriophonum and 1j;phonium in Ap­ the region and the exposure, they may pendix II). Although standard definitions be species-rich sites as well. For exam­ of corm and rhizome give distinct differ­ ple, in the region northeast of Tuxtla ences (see glossary, Appendix III) it is Guttierrez in the state of Chiapas, Mex­ not entirely clear how these are re­ ico, shady limestone cliffs may be the flected in the Araceae. Engler (1905- only areas which are rich in species. The 1920) defines the stem types of Araceae area is relatively dry, and shady lime­ in some detail (see especially the "Pars stone cliffs are substantially less arid than Generalis," Engler, 1920), but he does tree trunks. Limestone rocks and granite not include cormose as a stem type for boulders in forests are also important Araceae. By the strictest definition of since they represent obstacles to normal terms presented in a variety of glossaries tropical agriculture and are usually not and textbooks there is no question that cleared to grow crops. Aroids in dis­ genera like Amorphophallus produce turbed areas are thus more likely to be tubers. It is less apparent from the found growing on rocks. Steep road definitions of corms that this stem type banks also often have an established exists among the Araceae. Two fairly aroid flora, presumably established soon recent works have reported cormose after the roadcut was made and before plants for the Araceae. These include the remaining forest in the region was reports for Theriophonum (Sivadasan & cleared. The same situation exists for Nicolson, 1982) and for Colocasia and epiphytic species which persist in deep Typhonium (Pate & Dixon, 1982). ravines passed over by farmers (see Burnett (1984) also mentions corm below). production from the rhizomes of Aloca­ The epilithic habitat is as particularly sia. The stem types mentioned in Appen­ important for rheophytes (see above dix III have been taken from Engler under "rooted aquatics") as it is for ( 1905-1920) and also from the sources many genera which generally occur on quoted in the text. For a few poorly the forest floor (see Appendix I). Many known genera the stem type was de­ loosely-rooted species occur on the duced from closely related genera. forest floor or along the edges of forest just as commonly as on rocks. In Appen­ 3. Epilithic Plants dix I, there are 18 genera (16% of the Epilithic plants do not show a great total) classified as both terrestrial and preference for the surface on which they epilithic and the percentage is possibly grow. Many species grow as appressed much higher. The percentage of epi­ plants on tree trunks or on boulders. phytic genera which occur both on tree Porous limestone is particularly suitable trunks and on rocks is higher still (see for epilithic plants because of its ability below under "epiphytic plants"). to catch debris and to provide many interfaces for adequate rooting sites. 4. Epiphytic Plants Rarely is a species found only on lime­ Plants which are true epiphytes are stone (e.g., Anthurium reflexinervium naturally restricted to growth on trees or Croat sp. nov. ined., Colocasia gigantea shrubs and thus generally occur in 10 AROIDEANA, Vol. II, No.3 forests. They are almost invariably re­ juvenile plants of species which will stricted to primary forest or regrowth in become large are found on shrubs, primary forest, typically in humid to wet without the strong support needed for areas, and commonly persist in large further development, but they rarely trees, even after virtually all remaining persist there. Appressed hemiepiphytic forest is removed, but in such cases they climbers such as Monstera, Pbiloden­ often do not reproduce sexually. How­ dron, Rbodospatba and Syngonium re­ ever, vegetative reproduction is so suc­ main in a juvenile or preadult condition cessful in many epiphytic species that in shrubs since the right conditions of they may become more abundant in adequate support and availability of light such situations than they were in the are not met. The stems of such plants primary forest. Even in primary forest commonly fall free after a time, return to areas, sexually reproducing plants may the ground and seek a larger support. be rare, while vegetative reproduction is Alternatively, some species of Antbu­ very successful. For example, on Barro rium (e.g., A. kuntbii Poeppig, A. brevis­ Colorado Island in Panama (Croat, padix Croat,A.pentaphyllum (Aubl.) G. 1978), some species, such as Monstera Don and A. flexile Schott) normally dilacerata (K Koch & Sellow) K Koch occur on smaller trees, including small and Syngonium erythrophyllum Birdsey palms, and on shrubs. Again the reasons ex Bunting, are both rare as adults (only are not obvious, but they are species one collection of an adult plant known which do not need to attain much height for each on the island) while juvenile to flower and are generally small in plants are abundant, in general found overall size. Pbilodendron section Ptero­ throughout much of the trail system and miscbum also has species which appear covering the ground virtually every­ to be restricted to shrubs, e.g., P. auran­ where. tiifolium Schott andP. viaticum Croat & Epiphytic plants, at least in their early Grayum sp. nov., ined. stages of growth, show little preference Most epiphytes (including hemiepi­ for either rocks or trees ( commonly they phytes) prefer to grow on the lower part are referred to as epilithic, lithophytic or of tree trunks, commonly from one to rupicolous when occurring on the for­ four meters above the forest floor, proba­ mer). Most genera have been reported as bly because conditions of light are gen­ occurring on rocks, and those not previ­ erally adequate and humidity is high. ously reported as epilithic will probably Perhaps even more important, the prove to occur on rocks, at least in their amount of available nutrients and water initial developmental stages. Since all increase toward the base of the tree, as hemiepiphytic genera begin their devel­ all nutrients for true epiphytes are de­ opment in the soil (except a few species rived from runoff from above. Not sur­ of Pbilodendron which germinate on prisingly, the only epiphytes which trees and later produce roots which occur very high in the canopy are reach the ground), rocks or boulders are unusual, either in their ability to with­ often the first flat upright surface they stand the effects of drought (e.g., with encounter. Among climbing aroids there thicker, generally more succulent leaves are no known cases where rocks are and/or roots ), or in their ability to preferred to trees as the principal habi­ acquire nutrients. Some members of tat. Pbilodendron subgenus Meconostigma, Generally speaking, epiphytic plants for example, may grow very high in trees prefer to grow on larger trees. The and eventually produce adventitious reasons for this are unknown; perhaps roots which extend to the ground. the perching behavior of birds dispers­ Antburium gracile (Rudge) Lindley ing the fruits is the cause. Occasionally, often occurs high in the canopy, but T. Croat, 1988 11 when found there it is generally associ­ little distinction made by most ap­ ated with ant nests, which provide an pressed-climbing plants between rocks alternate source of nutrients from detri­ and trees. However, appressed climbers tus accumulated by the ants. It is also a are rarely seen on rocks, except at forest species with roots having a velamen, edges or in open areas in the forest, thus enabling it to better utilize atmos­ unless the rock is a very large one; this pheric humidity as a water source. Some no doubt due to the unavailability of members of Anthurium sect. Pachy­ light where smaller rocks occur. Alterna­ neurium are capable of growing rela­ tively, along stream banks, rocks provide tively high in the canopy or even on a more suitable habitat (permanency, rocks in areas where there is little better drainage) than steep banks. The overhead canopy to provide an adequate occurrence of appressed-climbing plants nutrient supply. This group is ideally located there is much more frequent. suited to conditions of low rainfall (and Hemiepiphytic Araceae are of two consequently low nutrient availability) types. Primary hemiepiphytes, the first and has short stems with a large, dense type, are those which start their lives as root mass, better able to catch rainfall true epiphytes and later make connec­ when it occurs and generally has rosu­ tion with the ground by means of long late leaves to catch and hold fallen roots which grow down from the plant debris. The debris accumulates in the and make contact with the ground. "basket" formed by the leaves and the Examples of this type are species such as upper, younger roots grow into this Philodendron solimoesense A. C. Smith debris, providing nutrients and water­ and P. megalophyllum Schott. holding capacity not available to most other epiphytic aroids. The second type start their lives on the ground and climb trees where they The epiphytic habit is perhaps even become adults and may lose their con­ more diverse in form than the terrestrial nection with the ground. These are habit, with both true epiphytes (those referred to as secondary hemiepiphytes which never have contact with the (Putz & Holbrook, 1986). Most Anthu­ ground), and hemiepiphytes (those rium and Philodendron species, as well which rely on a support on which to as Anadendrum, He terops is, Poth­ grow, but are also rooted in the ground). oidium, Pothos, Syngonium, many spe­ True epiphytes may on occasion become cies of Cercestis, Culcasia and the tribe hemiepiphytes by producing roots Monsteroideae are secondary hemiepi­ which reach the ground, and hemiepi­ phytes. phytes may become true epiphytes by Most hemiepiphytes must attain a losing their connection with the ground. certain stem girth before assuming adult The different classes of epiphytism will growth and flowering. About half of all be discussed in turn. hemiepiphytes, including Allosche­ 4.1 Hemiepipbytes. This discussion of mone, Amydrium, Epipremnum, Mon­ hemiepiphytes makes no distinction be­ stera, Rhaphidophora, Scindapsus and tween plants occurring on trees and Syngonium, have heteroblastic leaf de­ those occurring on rocks or on stones, velopment (leaf blades of radically differ­ even though the term "epiphytes" re­ ent shapes at different stages of develop­ fers specifically to the former. Perhaps a ment). One of the most radical examples new term needs to be coined, such as of heteroblasty occurs in Monstera "hemiepilythiphytes", to describe where some juvenile leaves (sect. plants using rocks as their support but Marcgraviopsis) are tightly appressed which are rooted in the ground. From ("shingle leaves") and others are free the standpoint of the plant (as already and spreading. In time, this growth form mentioned above) there seems to be gives way to intermediate, pre-adult 12 AROIDEANA, Vol. 11, No.3 leaves which are more nearly shaped like especially vines, often occurring in the the adult blades, but which usually are canopy of the forest (e.g., P. davidsonii entire, not perforate or lobed (see pho­ Croat and P. scandens K Koch & Sel­ tographs). Higher up on the stem adult low). Cercestis and Culcasia often leaves are later formed. This generally flower very near the ground, as do means genera with heteroblastic leaf Anadendrum, Pothoidium and Pothos. development must attain a suitable Spathiphyllum commutatum Schott, height on the tree trunk (generally 2.5 to and S. solomonense Nicolson, both of 5 m) to pass through the juvenile and which may be hemiepiphytic, flower preadult phases. Light availability ap­ near the ground. pears to be the most important criterion Internode length plays an important for a plant converting from juvenile to role in defining growth behavior of preadult leaves (Ray, 1987). Adult plants epiphytes, especially hemiepiphytes. may flower even on short tree stumps in Among hemiepiphytes, there are rela­ forest regrowth, or on rocks in open tively few vines or plants that are areas. Substrate is equally important markedly scandent. Species generally since some plants, under greenhouse have relatively long internodes when conditions with adequate light but with­ they are young and in an establishment out adequate support, have never been phase. As the plant approaches maturity, observed to change to their adult forms. internodes become shorter and thicker. Even if a concrete wall of adequate The transition may be fairly abrupt, but height (5 meters or more) is provided, generally occurs over a long succession some species grow upon the wall end­ of internodes. Once sexual maturity is lessly without becoming adult plants. reached, and assuming no such major Species of hemiepiphytes that do not disruptions as a treefall (which will undergo heteroblastic development greatly affect the available light or the have leaves which become increasingly plant's disposition), most plants indefi­ larger in size as the plant matures, but do nitely produce short internodes which not undergo marked changes in leaf grow slowly up the side of their support. morphology. Commonly, however, there There are a number of exceptions to this are minor differences in shape and often rule. Some species ofPhilodendron, e.g., coloration and texture as well. The P. linnaei Kunth, produce a series of non-heteroblastic genera of hemiepi­ short internodes with a tight rosette of phytic aroids include Anadendrum, leaves alternating with a series of long Cercestis, Culcasia (both of the latter internodes, which carries the plant apex sometimes merely terrestrial), Heterop­ higher up the tree where another rosette sis, some Monstera, Philodendron, Poth­ ofleaves is produced (Blanc, 1980). This oidium, Pothos,Rhodospatha and Spath­ process can be repeated indefinitely. iphyllum (the last almost always ter­ Philodendron /ragrantissimum (Hook.) restrial ). The height at which these Kunth has the same manner of growth genera reach flowering size varies but its rosettes are more widely spaced greatly, but is generally much lower than and are even sometimes found on differ­ those genera with heteroblastic develop­ ent trees. ment. Rhodospatha usually flowers at Other important exceptions to the heights similar to those of heteroblastic rule that hemiepiphytes remain in the genera (above 2.5 m), while Philoden­ "short internode stage" once they have dron is variable, with some species reached this developmental stage are flowering near the ground or even on those exhibiting heteroblasty (Syngo­ terrestrial plants about one meter above nium and genera in the tribe Monsteroi­ the forest floor (e.g., P. luteynii Croat & deae). These genera have the ability for Grayum, sp. nov. ined.) and others, repeated conversions from adult growth T. Croat, 1988 13 with short, thick internodes to juvenile preadapted for such conditions; they are growth with long, slender internodes often much more abundant in weedy (Ray, 1983a, 1983b, 1986, 1987). habitats. Scandent hemiepiphytes begin their The same situation often applies to growth in usually the same manner as areas where part of the forest has been short stemmed appressed-climbers, but cut away, such as a new road. Most differ in that the production of longer hemiepiphytes thrive particularly well in internodes continues perpetually. As the these partially-shaded forest edges. plant matures, the stems usually also Open areas along rivers and smaller increase in diameter with only moderate streams offer similar growing conditions. decrease in length of internodes. The neotropics have a much higher On appressed-climbers, usually only percentage of hemiepiphytic genera that the uppermost nodes (commonly fewer are than do the paleotropics. Of all the than ten) are leaf-bearing, but much of genera which are predominantly epi­ the non-leafy stem is intact and acts as phytic, only Stenospermation is never continued physical support and proba­ hemiepiphytic. Anthurium, though it bly will also have still active roots for has numerous terrestrial species and a absorbing water and nutrients. The most few hemiepiphytic members, largely active roots are always borne on the consists of true epiphytes. Philodendron leafy portion of the plant. However, is largely hemiepiphytic, with only a few hemiepiphytic vines are leafy through­ true epiphytes which start their lives as out all or much of their length and their epiphytes and remain epiphytic (e.g., P. roots are likewise more scattered and wendlandii Schott and P. davidsonii occur only at the nodes. They are not Croat). aggregated in a manner allowing debris In contrast to the American tropics, to be easily trapped among them, and are Africa and the Malagasy region have no therefore less successful in providing true epiphytic genera (Remusatia is themselves with a nutrient supply. Per­ sometimes epiphytic in Asia and Ma­ haps for this reason the number of dagascar) and only four hemiepiphytic hemiepiphytic vines is relatively low genera: Cercestis and Culcasia (en­ compared to the number of appressed demic), Pothos and Rhaphidophora, epiphytes. Still, it cannot be denied that which are indigenous but better repre­ many hemiepiphytic vines (e.g., Philo­ sented in Asia. dendron scandens K. Koch & Sellow, Four epiphytic genera occur in Aus­ Epipremnum pinnatum (L.) Engl. and tralia: Epipremnum, Pothos, Pothoid­ Pothos scandens L.) are among the most ium and Rhaphidophora. All are hemi­ widespread and successful species. epiphytes. The percentage of hemiepi­ In the New World all of the hemiepi­ phytes in the Australian flora is rather phytic genera occur principally in pri­ high (five out of 17). All Australian mary, mostly humid to wet forests. genera (and most of the species as well) These genera include Alloschemone, except Gymnostachys, are widespread Anthurium (few species), Heteropsis, in Asia. Asia has eight indigenous genera Monstera, Philodendron, Rhodospatha of epiphytes, and all are hemiepiphytic. and Syngonium. Some species, espe­ These include Amydrium, Anaden­ cially of Monstera and Syngonium and drum, Epipremnum, Rhaphidophora, also of Philodendron, may be abundant and Scindapsus. Spathiphyllum com­ in weedy situations, commonly along mutatum Schott (based on Croat 33032) fence rows and on trees in coffee has been observed as an incidental plantations. In natural habitats they gen­ hemiepiphyte in the Philippines. Most erally begin their growth in areas of are members of the understory or they natural disturbance and so are occur along primary forest edges or in 14 AROIDEANA, Vol. 11, No.3 regrowth in humid to wet areas. Several Anthurium (e.g., A. scandens (Aubl.) genera, including Amydrium, Epiprem­ Engl. and A. interruptum Sodiro) have num, Rhaphidophora and Scindapsus, elongate internodes, but with the lower­ are members of the subfamily Monsteroi­ most internodes short and densely deae and have heteroblastic leaf devel­ rooted for support and for debris collec­ opment and alternating adult-juvenile tion. growth phases. The only remaining The overwhelming majority of true hemiepiphytic genus, Anadendrum, has epiphytes are neotropical; the paleotrop­ short to moderately long internodes and ics having comparatively few epiphytic is (often somewhat) scandent. Of the species (see above). estimated 700 indigenous Asian species As in the case of hemiepiphytes, many only about 22% are generalized epi­ true epiphytes are also found on rocks or phytes (about 160 species, nearly all of boulders, when growing in or at the edge which are hemiepiphytic) while of the of a primary forest. Epiphytic species of estimated 2,206 indigenous neotropical Anthurium, Philodendron and Steno­ species, an estimated 86% (1,000 hemi­ spermation may sometimes occur epil­ epiphytes and 910 true epiphytes) are ithicly. generalized epiphytes. This astounding At higher elevations, many epiphytic difference between the araceous flora of species are frequently found in situations the neotropics and the paleotropics is where they are neither on trees nor on mostly due to Anthurium and Philoden­ rocks. These habitats could theoretically dron, the two largest genera in the be classified as terrestrial, and indeed in family. Both are restricted to the these situations the plants are often neotropics and both are chiefly epi­ actually rooted into the soil. Neverthe­ phytic. less, these rarely constitute terrestrial 4.2 True epiphytes. This life form habitats as found in the hot, lowland group constitutes the largest single tropics, where little debris is present on group of aroids in the neotropics (about the ground except at the end of the dry 620 species). The true epiphytes in the season. Instead, these plants are usually neotropics consist largely of Anthurium rooted in a deep mat of debris due to species, but also include all species of slow humus breakdown at higher eleva­ Stenospermation and some species of tions. Bryophytes may be abundant as Philodendron. Hemiepiphytic genera well, contributing further to substrate are sometimes disconnected from the formation for the root systems of aroids soil and thus become true epiphytes, and other plants. In most cases, such since they are capable of persisting in "terrestrial plants", which are normally that state indefinitely. An unusual situa­ epiphytic, are also found on steep slopes tion with a few true epiphytes is their where drainage is good and where the ability to eventually send roots to the habitat duplicates the normal epiphytic ground and become hemiepiphytes (e.g., habitat. As mentioned earlier, normally P. radiatum Schott and P. solimoesense epiphytic species may also inhabit steep A. C. Smith). These plants often grow banks of streams or occur on roadcuts, very slowly for years before being large where drainage is good and light is not enough to send roots to the ground. too intense throughout the day. Particularly surprising in this respect is Comparison of Different Phytogeo­ P. solimoesense, as it often grows in very graphic Regions: exposed situations high in the canopy While representation of most life where falling debris is more limited. forms of Araceae are found in each major Most true epiphytes have short inter­ continental area of America, Africa and nodes and grow more slowly than the Asia, there are certain significant similar­ average hemiepiphyte. Some species of ities and differences. The Mediterranean T. Croat, 1988 15 region and Europe have only terrestrial, medium-sized genera (60 or more spe­ mostly tuberous life forms. North Amer­ cies) than America (Alocasia: 70, Amor­ ica has only terrestrial, principally phophallus: 100, Arisaema: 150, aquatic life forms. Temperate and sub­ Homalomena: 140 and Rhaphidophora: tropical South America has principally 60), but has no truly large genera like tuberous life forms. Tropical Africa has Anthurium (1,000) or Philodendron predominantly tuberous life forms. Trop­ (700) in the American tropicS. Aside ical America, as well as tropical parts of from these two large genera, the Africa and Asia, has species primarily neotropics have few genera with as inhabiting primary forest, while America many as 60 species, though a few genera overall has a preponderance of hemiepi­ have a moderate number, includingDieJ­ phytic and epiphytic life forms. Among Jenbachia (50), Monstera (60), Rho­ hemiepiphytic plants, appressed-climb­ dospatha (67), Syngonium (36) and ers predominate, while true vines are a Xanthosoma (45). minor component. Appressed epiphytes are dominated by genera which have heteroblastic leaf development. In SUMMARY strong contrast to the neotropics, Asia The Araceae comprises a complex has only a few true epiphytes (probably group in terms of life forms and ecolo­ fewer than six). Tropical America has gies. Life forms range from submerged to relatively few rheophytic genera, while free-floating, from emergent aquatics to Asia has many. Africa has principally terrestrial plants, and from epilithic to terrestrial life forms, no true epiphytes, epiphytic forms. Life zones range from and few appressed hemiepiphytes or tropical dry through tropical swamps, hemiepiphytic vines. Asia has more cloud forests, cold, windswept montane rooted aquatic genera, and especially plains, and semi-arid to arid coastal species, than does America. Africa has plains. few rooted aquatic plants but a moder­ The family is widespread with almost ately rich assortment of tuberous genera. equal numbers of genera occurring in African genera are rich in plants adapted the Old and New Worlds, although the to dry conditions, with no pronounced majority of species are found in the New diversity in any genus. Although rich in World tropics. Distinct differences are genera, Asia has only moderate specia­ shown phytogeographically as well as at tion in many genera. Asia has more the suprageneric taxonomic level. 0 16 AROIDEANA, Vol. 11, No.3

Pistia stratiotes L.; a free-floating aquatic, Las Alaotra, Madagascar. Photo: J. Bogner.

Aridarum nicolsonii Bogner; a typical rheophyte growing on sandstone rocks in the Sungai Tambak, Mt. Santubong, Sarawak. Photo: J. Bogner. T Croat, 1988 17

Philodendron scandens K. Kock and Sellow; hemiepiphyte appressed-climbing. 18 AROIDEANA, Vol. 11 , No.3

Anthruium clidemioides StandI. ssp. pacificum Croat and Grayum; hemiepiphyte appressed-climbing. T. Croat, 1988 19

Rhodospatha moritziana (Schott) Carlephyton diegoense Bogner; terres­ Croat; caulescent terrestrial. trial tuberous, growing in humus collec­ tions of limestone in the Montagne des Franc,:ais, Madagascar. Photo: J. Bogner.

Bognera recondita (Madison) Mayo and Spathicarpa gardneri Schott; tuberous Nicolson; acaulescent terrestrial, grow­ terrestrial, growing on the forest floor in ing in sandy soil in the rainforest in terra northern GOias, Brazil. Photo: J. Bogner. firme at the Rio Javari near Lago Cauxi, Amazonas, Brazil. Photo: J. Bogner. 20 AROIDEANA, Vol. 11 , No.3

Dracontiunz pittieri Engl.; tuberous terrestrial.

Zonzicarpella anzazonica Bogner; tuberous terrestrial, growing in loamy soil in the rainforest in terra firme at the Rio Javari, Amazonas, Brazil. Photo:). Bogner. T Croat, 1988 21

Syngonium hoffmanii Schott; hemiepiphyte appressed-climber.

APPENDIX I

ARACEAE Homalomena 17 Estimated number of species per Jasarum 1 genus of Araceae. Mangonia 2 Monstera 60 Neotropical Philodendron 700 Alloschemone 1 Pistia 1 Aphyllarum = Caladium Rhodospatha 67 Anthurium 1000 Spathantheum 1 Asterostigma 5 Spathicarpa 7 Bognera 1 Spathiphyllum 60 Caladium 17 Stenospermation 60 Chlorospatha 15 Synandrospadix 1 Dieffenbachia 50 Syngonium 36 Dracontioides 1 Taccarum 5 Dracontium 18 Ulearum 2 Echidnium = Dracontium Urospatha 20 Filarum 1 Urospathella = Urospatha Gearum 1 Xanthosoma 45 Gorgonidium 3 Zomicarpa 3 Heteropsis 13 Zomicarpella 1 22 AROIDEANA, Vol. 11, No.3

Extraneotropical Genera Heteroaridarum 1 Holochlamys 3 Acorus 2 Homalomena 130 Aglaodorum 1 Hottarum 4 Aglaonema 21 Lagenandra 14 Alocasia 70 Lasia 2 Ambrosina 1 Lysichiton 2 Amorphophallus 100 Nephthytis 5 Amydrium 4 Orontium 1 Anadendrum 9 Pedicellarum 1 Anaphyllum 2 Peltandra 3 Anaphyllopsis 3 Phymatarum 2 Anchomanes 10 Pinellia 7 Anubias 8 Piptospatha 10 Aridarum 7 Pistia 1 Ariopsis 1 1 Arisaema 150 Podolasia Pothos 50 Arisarum 3 Arophyton 7 Plesmonium = Amorphophallus 1 Arum 26 Pothoidium Biarum 21 Protarum 1 Bucephalandra 2 Pseudodracontium 7 Calla 1 Pseudohydrosme 2 Callopsis 1 Pycnospatha 2 Carlephyton 3 Remusatia 3 Cercestis 10 Rhaphidophora 60 Colletogyne 1 Rhektophyllum = Cercestis Colocasia 8 Sauromatum 2 Cryptocoryne 50 Schismatoglottis 100 Culcasia 20 Spathiphyllum 3 Cyrtosperma 11 Steudnera 8 Diandriella = Homalomena Stylochaeton 21 Dracunculus 2 Symplocarpus 2 Eminium 6 Scindapsus 25 Epipremnum 15 Theriophonum 5 Gonatanthus 1 Thomsonia = Amorphophallus Gonatopus 5 Typhonodorum 1 Gymnostachys 1 Xenophya = Alocasia Hapaline 5 Zamioculcas 1 Helicodiceros 1 Zantedeschia 6 T. Croat, 1988 23

APPENDIX II

ECOLOGY OF ARACEAE [Suprageneric classification based on Grayum ( 1984)1

NEW WORLD cloud forests compared with other aroid genera at middle elevations (Croat & Subfamily Pothoideae Grayum, loco cit.). Tribe Spathiphylleae Spathiphyllum Tribe Monstereae Sub tribe Heteropsidinae Principal Life Form: Heteropsis terrestrial Alternate Life Form: Principal Life Form: hemiepiphytic hemiepiphytic epilithic Alternate Life Form: Ecology: Understory terrestrial, epilithic rhizomatous herbs in primary forest or Ecology: Scandent plants on trees or regrowth, usually in wet to swampy less frequently on rocks, usually in the areas or along streams in full sun or lower canopy or on tree trunks in partial shade, on rocks in streams, rarely primary forest (Croat & Grayum, loco on well-drained slopes; open, swampy cit.). Sometimes producing slender roots areas; rarely somewhat hemiepiphytic which hang down toward the ground; (Croat & Grayum, in press). Spath­ the subterete seeds germinate in the soil iphyllum spp. are facultative rheophytic (M. Grayum, pers. comm.). (van Steenis, 1981). Subtribe Monsterinae Tribe Anthurieae Monstera Anthurium Principal Life Form: Principal Life Form: epiphytic epiphytic hemiepiphytic Alternate Life Form: terrestrial Alternate Life Form: epilithic terrestrial hemiepiphytic epilithic Ecology: Mostly appressed-climbers Ecology: Appressed-climbers with on trees in understory of primary forest, usually short internodes as adults, revert­ less frequently on higher branches; ing to juvenile or preadult growth upon rarely terrestrial in the understory, fre­ disturbance; usually on trees in under­ quently on rocks, especially abundant in story of primary forest, less frequently open areas, along roadcuts, streams and canopy vines with pendent flowering at the edges of treefalls; less frequently branches; occasionally in regrowth, on terrestrial under shrubs in dry forest or fence rows; more abundant in open areas in open sandy areas; rarely along stream along forest edges (Croat & Grayum, loco banks; common at lower and middle cit.); seeds germinate in soil, juvenile elevations and especially common in plants terrestrial and skototropic. 24 AROIDEANA, Vol. 11, No.3

Alloscbemone bogs, pond margins or swampy grass­ lands from sea level to 1,300 m (Hegi, Principal Life Fonn: 1909; Fernald, 1950; Hotta, 1970). The hemiepiphytic boggy areas may be open to full sunlight Ecology: Appressed-climbers on trees or beneath a tree layer (Croat & Grayum, in understory of primary forest (Croat & loco cit.). Grayum, loco cit.). Tribe Montrichardieae Stenospermation Montricbardia Principal Life Fonn: Principal Life Fonn: epiphytic rooted aquatic Alternate Life Fonn: Ecology: Shrub-like herb with stems terrestrial erect and spongy, occurring in warm epilithic standing or slowly moving fresh water at low elevations, often forming dense to Ecology: Appressed growth with usu­ solid stands along the margin of water ally short internodes, rarely somewhat courses; sometimes stranded above scandent or terrestrial on steep banks; water levels during the dry season; fruits usually in primary cloud forest at mid to water-dispersed (Croat & Grayum, loco high elevations, usually on tree trunks cit. ). and lower branches, sometimes on rocks; less frequently in lowland rain­ forest; sometimes on steep road banks in Tribe Zomicarpeae cloud forest areas; germination of seeds Pilarum in trees (Croat & Grayum, loco cit.). Principal Life Fonn: terrestrial Rbodospatba Ecology: Tuberous understory herb of Principal Life Fonn: primary forest. hemiepiphytic Alternate Life Fonn: Ulearum terrestrial Principal Life Fonn: epilithic terrestrial Ecology: Appressed-climbers, usually Ecology: Understory rhizomatous in primary lowland to mid-elevation herb growing on leaf litter on "terra forests, usually on tree trunks; less fre­ frrme" of primary forest. quently terrestrial on steep banks, espe­ cially on stream banks; germination of Zomicarpella seeds in soil with juvenile plants often blanketing much of the forest floor Principal Life Fonn: (Croat & Grayum, loco cit.). rhizomatous Ecology: Tuberous creeping rhizoma­ Subfamily Philodendroideae tous understory herb in leaf litter on Tribe Calleae "terra frrme" (unflooded areas) of pri­ Calla mary forest? Principal Life Fonn: terrestrial Zomicarpa Ecology: Herb with long creeping rhi­ Principal Life Fonn: zomes growing usually in cold water terrestrial T. Croat, 1988 25

Ecology: A tuberous herb occurring in other vegetation (E. Zardini, pers. the understory of seasonal forest in comm.), occurring up to 2,000 m; flow­ Ceara, otherwise in Bahia; where it ering and leafing out in September and grows in the rainy season and is dormant early October at the beginning of the in the dry season O. Bogner, pers. rainy season. comm.).

Taccarum Tribe Homalomeneae Homalomena Principal Life Form: terrestrial Principal Life Form: terrestrial Ecology: Tuberous; growing in damp soil in understory or on roadsides, in Ecology: Usually understory with humid but often seasonally dry areas; short, erect (sometimes creeping) stems sometimes in open areas of "campo occurring in primary forest, frequently cerrado" (a type of shrub forest) in wet areas such as along small forest (Chodat & Vischer, 1920). streams. Often on roadbanks in partial shade; less frequently on well-drained slopes in tropical moist forest (H. wend­ Gorgonidium landii Schott) (Croat & Grayum, loco cit.). Principal Life Form: terrestrial Tribe Spathicarpeae Ecology: Tuberous; occurring in sea­ Mangonia sonally dry areas at 2,500-3,000 m; G. vargasii Bogner & Nicolson has been Principal Life Form: collected in stony cultivated fields near terrestrial fences O. Bogner, pers. com.). Ecology: Tuberous herb occurring in seasonally dry areas (Croat & Grayum, Gearum loco cit.). Principal Life Form: Asterostigma terrestrial Principal Life Form: Ecology: Plants with rhizomatous tu­ terrestrial bers growing in inundated areas (proba­ bly after heavy rains) and with hysteran­ Ecology: Tuberous herb occurring thous flowering (]. Bogner, pers. usually as an understory plant in primary comm.). forest occurring in cool mountain val­ leys (Madison, 1978), often on steep slopes, ranging from near sea level to Spathantheum 2,300m. Principal Life Form: terrestrial Synandrospadix Ecology: Tuberous; usually loosely Principal Life Form: rooted in the understory, growing on terrestrial deposits of humus on rocks, or under the Alternate Life Form: edges of cliffs and in rock crevices along road banks in shady areas in Bolivia epiphytic (Croat & Grayum, loco cit.) or in moun­ Ecology: Tuberous herb in dry shrub tain prairies up to 2,400 m in northern forest, sometimes in sandy soil with little Argentina O. Crisci, pers. comm.). 26 AROIDEANA, Vol. 11, No.3

Spathicarpa epiphytes ). At least one species has adopted to dry conditions by rooting Principal Life Fonn: into tank bromeliads (Mayo & Barroso, terrestrial 1979). Ecology: Tuberous plants with tubers, rhizomes or rhizomatous tubers occur­ Tribe Dieffenbachieae ring in the understory of humid or marshy forests; S. hastijolia Hook. has a Dieffenbachia wide range of ecological preferences Principal Life Fonn: including dry forest (caatinga) where terrestrial the vegetative parts may die back during periods of drought O. Crisci, pers. Alternate Life Fonn: comm.). rooted aquatic Ecology: Caulescent herb usually in Tribe Philodendreae the understory and along clearing edges Philodendron or stream banks in humid to wet forest; often colonial, forming dense local Principal Life Fonn: stands, frequently on well-drained slopes hemiepiphytic or in rocky areas along streams; rarely in Alternate Life Fonn: standing water in almost permanently epiphytic swampy areas in ditches or areas that are terrestrial annually flooded for a large part of the epilithic year (Croat & Grayum, loco cit.). Ecology: Rhizomatous to scandent herbs with a broad range of ecological Tribe Bognereae requirements; mostly appressed-climb­ Bognera ers on trees (less frequently on rocks) in Principal Life Fonn: the understory, especially in humid for­ terrestrial ests at low to middle elevations; some­ times vines growing over low vegeta­ Ecology: Rhizomatous understory tion, especially along edges; rarely as herb growing on leaf litter or sandy soil terrestrial herbs in deep shade or as high O. Bogner, pers. comm.) in dark, humid canopy vines; infrequently in aquatic forests (Madison, 1980). situations (e.g., P. brevispathum Schott, P. muricatum Willd. ex Schott, P. undu­ latum Engl.); some groups (e.g., many Subfamily Colocasioideae sect. Meconostigma) as erect Tribe Caladieae pachycaulous tree-like plants in open, Subtribe Jasarinae usually dry areas, especially on pure sand Jasarum deposits; more frequently as decumbent Principal Life Fonn: plants on rocky exposed areas (e.g., P. submerged aquatic callosum K Krause) or on rocky cliffs (e.g., P. henripittieri Bunting) (Croat & Ecology: Totally submerged in moder­ Grayum, loco cit.). Also some species (P. ately slow moving black-water streams wendlandii Schott) are true epiphytes with a pH of 5.0-5.4 in shade or in full with a rosulate growth pattern. Still sun; flowering scapes emerging from the others, e.g., P. solimoesense A.C. Smith, water for pollination (Bogner, 1977; begin their life as true epiphytes and 1985); mostly Jasarum grows in the eventually produce long roots which mud on the stream floor, occasionally reach the ground (thus becoming hemi- between rocks O. Bogner, pers. comm.). T. Croat, 1988 27

Subtribe Scaphispathinae full sun or partial shade ( Croat & Scaphispatha Grayum, loco cit.); rarely epilithic in X. caladioides Grayum (Grayum, 1986). Principal Life Form: terrestrial Chlorospatha Ecology: Tuberous herb occurring in dry, open, grassy areas or in temporary Principal Life Form: wet spots; appearing after heavy rains terrestrial and flowering and fruiting promptly O. Ecology: Rhizomatous understory Bogner, 1980a). plants in wet ravines, well-shaded creek beds or in boggy areas in the forest, Subtribe Caladiinae generally at middle to low elevations. Caladium Principal Life Form: Subtribe Syngoniinae terrestrial Syngonium Alternate Life Form: Principal Life Form: epilithic hemiepiphytic Ecology: Usually an understory tuber­ Alternate Life Form: ous herb in open areas in the forest, on epilithic creek banks, being especially common in epiphytic areas of semideciduous forest, where Ecology: Usually appressed-climbers they lose their leaves during the dry on tree trunks in the understory of season and go dormant; occasionally usually moist to wet (rarely dry) primary epilithic with tubers wedged into rocks forest; frequent in disturbed areas such along creeks or on steep slopes. Cala­ as regrowth or even weedy areas such as dium is well adapted to disturbance, in fence rows and on road banks; juve­ often proliferating in areas along roads in nile plants terrestrial, growing skoto­ partial shade; ranging from near sea level tropically to the nearest large tree; adult to at least 1,000 m. (Croat & Grayum, plants converting to juvenile form on loco cit.). disturbance (Ray, 1983b, 1986, 1987).

Xanthosoma Subfamily Lasioideae Principal Life Form: Tribe Oronteae terrestrial Subtribe Symplocarpiinae Symplocarpus Alternate Life Form: epilithic Principal Life Form: terrestrial Ecology: Rhizomatous or tuberous; ecologically variable, with some species Ecology: Subterranean rhizomatous being understory herbs in moist to wet herbs occurring principally in wet areas forests, especially along and in ravines in meadows, woods, swamps, peat bogs, (e.g., X. robustum Schott, X. peltatum usually on level ground or sometimes on Bunting, X. tarapo tense Eng!.) and oth­ steep slopes or in ravines, often on rich ers occupying areas of tropical moist to soil in forest or in regrowth (Li, 1979; tropical dry forest and losing their leaves Croat & Grayum loco cit.); sometimes in during all or part of the dry season; some sunny open areas (Nasir, 1978), open species occur in open marshy areas in steppe or subdesert (Li, 1979). 28 AROIDEANA, Vol. 11, No.3

Lysicbiton swamps along the Caribbean coast of Central America and in lowland Ama­ Principal Life Form: zonia; rarely in areas which are occasion­ terrestrial ally not wet (Engler, 1911). Ecology: Rhizomatous; occurring in swampy hardwood forests or occasion­ Dracontioides ally in disturbed forests (Hulten & St. John, 1931); often in broad marshy Principal Life Form: creekbeds or swampy meadows (Croat aquatic & Grayum, loco cit.). Ecology: Swampy herb with spongy rhizome occurring in standing water Subtribe Orontiinae (Mayo, 1978; Croat & Grayum, loco cit.). Orontium Dracontium Principal Life Form: aquatic Principal Life Form: terrestrial Ecology: Herbs on sandy, muddy and peaty shores or rooted in the bottom of Ecology: Tuberous herb in seasonally shallow fresh water in swamps and lakes dry areas; leaves deciduous annually; (Fernald, 1950); having a broad ecologi­ principally occurring in tropical moist cal amplitude from the standpoint of and tropical dry forest life zones, less temperature as it ranges from Florida to frequently in wetter areas; locally abun­ Massachusetts; the plant is submerged, dant but infrequently seen; plants usually with most of the leaves exerted; inflo­ flowering hysteranthously, then produc­ rescences protrude above the water at ing usually a single leaf (Croat & flowering, usually in the spring. Grayum, loco cit.).

Tribe Lasieae Subfamily Aroideae Subtribe Dracontiinae Tribe Pistieae Anapbyllopsis Pistia Principal Life Form: Principal Life Form: terrestrial free-floating aquatic Alternate Life Form: Ecology: Floating aquatic, reproduc­ aquatic ing principally vegetatively; growing along water courses (drainage ditches Ecology: Rhizomatous understory and ricefields, etc.) in mostly fresh water herb in primary forest, especially in systems at low elevation, occasionally swampy, sandy areas along streams; the completely covering the surface of the short erect stems are at least partly area inhabited (Croat & Grayum, loco underwater for part of the year (Bogner, cit. ). pers. com.). Hay (1988) reported A americana (Eng!.) A. Hay to grow in the Tribe Arisaemateae shade of swamp forests and in a partially Arisaema flooded area along a road. Principal Life Form: Urospatba terrestrial Principal Life Form: Ecology: Tuberous or rarely rhizoma­ aquatic tous tuber; New World species usually occurring in primary forest areas as an Ecology: Rhizomatous herb in coastal understory plant in open woodlands, T. Croat, 1988 29 edges of forest, wet woods or boggy Alternate Life Form: areas or on slopes, usually in deep terrestrial alluvium or rocky areas (Fernald, 1950; epilithic Steyermark, 1963; Correll & Correll, Ecology: Rhizomatous to somewhat 1972; Croat & Grayum, loco cit.). scandent herbs, mostly with elongate internodes; occurring mostly in lowland primary vegetation in the understory; OLD WORLD sometimes in secondary forest, gallery forest, clearings, shallow streams (on AFRICA (Endemic genera only) rocks) or in wet areas along streams (Hepper, 1968; Knecht, 1983; Croat & Grayum, loco cit.). Growth forms vary Subfamily Pothoideae from erect to semierect terrestrial plants Tribe Potheae to hemiepiphytic climbers (Knecht, 1983). Pothos (discussed under Asia) Tribe Nephtytideae Tribe Zamioculcadeae Nephthytis Zamioculcas Principal Life Form: Principal Life Fonn: terrestrial terrestrial Ecology: Understory herbs with Ecology: Seasonally dormant herbs creeping rhizomes, growing in dense with a more or less rhizomatous tuber shade, in lowland primary forest, secon­ (Mayo, 1985); occurring in spreading dary forest or gallery forest, sometimes clumps in the understory of coastal occurring on granitic rocks (Knecht, forest, in sandy soil rich in humus or in 1983); N. hallaei (Bogner) Bogner humus deposits between rocks (Ober­ grows on a layer of humus in sandy soil; meyer & Strey, 1969); adapting locally N. swainei Bogner occurs on acidic, to either open sunny areas or to dark nutrient poor soil (Bogner, 1980b). understory (M. Bleck, pers. comm.). Cercestis Gonatopus Principal Life Form: hemiepiphytic Principal Life Form: terrestrial Alternate Life Form: terrestrial Ecology: Tuberous understory -herbs in dune forest in northern Natal; G. Ecology: Rhizomatous or climbing un­ angustus N.E. Br. occurs in shady rocky derstory herbs, mostly appressed hemi­ pockets in low-lying "bushveld" area of epiphytic, (sometimes terrestrial) or eastern Transvaal (Obermeyer, 1977); scandent; C. ivorensis A. Chev. occurs in G. boivinii (Oecne.) Hook.f occurs at dense shade, while C. ajzelii Schott the edges of virgin forest and within the requires more light and occurs in secon­ forest along ravines (Peter, 1930). dary forest (Knecht, 1983).

Tribe Callopsidae Subfamily Philodendroideae Callopsis Tribe Culcasieae Culcasia Principal Life Form: terrestrial Principal Life Form: hemiepiphytic Ecology: Small rhizomatous herbs in 30 AROIDEANA, Vol. 11, No.3 the understory of lowland evergreen Tribe Zantedesheae forest, bearing thick spreading roots; Zantedeschia occurring at 45-800 m (Mayo, 1985). Principal Life Form: terrestrial Tribe Anchomaneae Ecology: Well-rooted rhizomatous or Anchomanes tuberous herbs (Mayo, 1985) perennials with variable ecological requirements; Principal Life Form: Z. rehmannii Engl. occurs on dry, rocky terrestrial hills (Traub, 1949), or in swampy Ecology: Rhizomatous sparsely leaved ground, along forest edges or roadsides herbs usually in open areas in humid usually in sunny areas Oeppe, 1975); Z. forests, along edges of forest or in aethiopica (L.) Spreng. prefers swampy areas Oeppe, loco cit.). clearings; sometimes in savanna forest (Hepper, 1968), the bases of isolated hills (Knecht, 1983), abandoned fields Tribe Peltandreae and on roadbanks. Plants seasonally die 1}phonodorum back and go dormant (Mayo, 1985). Principal Life Form: Engler (1911) described Anchomanes aquatic as having tubers rather than. rhizomes. Ecology: Robust rhizomatous aquatic in standing fresh water swamps occur­ Pseudohydrosme ring from near sea level to 900 m; fruits develop and germinate prematurely Principal Life Form: within the spathe, giving the capability terrestrial of prompt establishment after dispersal. Engler ( 1915) reports the genus to have Ecology: Tuberous; in understory in oblong horizontal tubers. deep shade in the humus layer over sandy loam soils; occurrence extremely rare. (Bogner, 1981a). Tribe Arophyteae Arophyton

Tribe Anubiadeae Principal Life Form: terrestrial Anubias Alternate Life Form: Principal Life Form: epilithic terrestrial epiphytic Alternate Life Form: Ecology: Tuberous; growing in humus aquatic deposits in the understory of forests, sometimes in humus deposits over lime­ Ecology: Rhizomatous herb in wet, stone (A. crassifolium (S. Buchet) shady areas of the understory in forest, Bogner) or over granite or gneiss, less especially on stream banks, in river beds frequently as an epiphyte (A. buchetii in either rocky areas or mud (Croat & Bogner and sometimes A. tripartitum Grayum, loco cit.); plants may be com­ ]um.)(Bogner, 1975). pletely submerged (Hutchison & Dalziel, 1936; Crusio, 1979) or on rotting logs ( Crusio, loco cit. ). Three species are Carlephyton possibly truly rheophytic (van Steenis, Principal Life Form: 1981). terrestrial T. Croat, 1988 31

Ecology: Tuberous; occurring in meters long and may quickly invade shady places in moderately acidic humus areas by this manner. deposits (pH 5.4-5.8) over limestone or basalt in deciduous forests (Bogner, loco Tribe Stylochaetoneae cit. ). Stylocbaeton Principal Life Form: Colletogyne terrestrial Principal Life Form: Ecology: Seasonally dormant rhizoma­ terrestrial tous herbs, sometimes with stems Ecology: Tuberous; occurring in stoloniferous (Mayo, 1985). Engler shady places in moderately acidic humus (1920) reports it to have rhizomatous deposits overlaying calcareous rocks tubers. (Bogner, loco cit.). Subfamily Aroideae Tribe Thomsonieae (Amorphophalleae) Subfamily Colocasioideae Amorpbopballus (see Asia) Tribe Colocasieae Subtribe Protarinae Protarum Tribe Arisareae Arisarum (see Mediterranean Re­ Principal Life Form: gion) terrestrial Alternate Life Form: Tribe Ambrosineae epilithic Ambrosina (see Mediterranean Re­ gion) Ecology: Tuberous; growing in the forest understory on hills where it pro­ Tribe Arisaemateae trudes from the humus layer on or Arisaema between granitic rocks (Bogner, 1973b) in a region with an evenly distributed Principal Life Form: rainfall of 250 cm per year and relatively terrestrial constant temperature of 18 degrees Alternate Life Form: Centigrade. epiphytic

Subtribe Remusatiinae (see Asia) Ecology: Growing as a terrestrial tu­ berous herb principally in damp shady sites in forested areas in bamboo thickets Subfamily Lasioideae along field borders, margins of thickets Tribe Lasieae or hedges, sometimes over limestone for Subtribe Dracontiinae A. flavum (Forssk.) Schott, frequent on Cyrtosperma (see Asia) rocky slopes CA. enneapbyllum Hochst. ex A. Rich.) infrequently epiphytic for A. Lasimorpba scbimperianum Schott and A. ruwen­ zoricum N.E. Br. (Mayo & Gilbert, Principal Life Form: 1986). terrestrial Ecology: Rhizomatous; inhabiting for­ Tribe Areae est edges and in swamps and ravines in Dracunculus (see Mediterranean savanna country (Hepper 1968); Bogner Region) (1987) reports that this species pro­ duces long underground stolons several Sauromatum (see Asia) 32 AROIDEANA, Vol. 11, No.3

Eminium (see Mediterranean Re­ Tribe Potheae gion) Potbos Principal Life Form: Biarum (see Mediterranean Region) hemiepiphytic Ecology: Generally scandent herbs usually occurring in primary forest or ASIA & AUSTRALIA regrowth Oohns & Hay, 1981), usually in humid areas; less frequently on steep Subfamily Gymnostachydoideae banks (Ridley, 1925); usually occurring at low to moderately low elevations but Gymnostachys ranging up to 2,400 m in southwestern Principal Life Form: China (Li, 1979). terrestrial Ecology: An evergreen herb occur­ Potboidium ring in open shrublands, usually at the Principal Life Form: border of shrubs (Bailey, 1902) or in hemiepiphytic sheltered gullies, rain forests (Beadle, Evans & Carolin, 1982) and in wetter Ecology: Scandent herb occurring in types of Eucalypt forests (Cribb & Cribb, the understory of humid primary forest. 1981). It is also reported from wet sclerophyll forest, preferring shales and Tribe Anadendreae basalt soils but soils are fairly deep Anadendrum (Shelton, 1980). Williams (1979) re­ Principal Life Form: ports Gymnostachys to be common on hemiepiphytic cool southerly slopes and in cool moist gullies "in areas of sandstone ridges Alternate Life Form: where soils are derived from the weath­ epilithic ering of the sandstone." Ecology: Scandent; rooting on trees, shrubs or on rocks in moist to wet Subfamily Pothoideae forests, often along streams (Ridley, Tribe Spathiphylleae 1925). SpatbiPbylium (see New World) Tribe Monstereae Subtribe Monsterinae Holocblamys Amydrium Principal Life Form: Principal Life Form: terrestrial hemiepiphytic Alternate Life Form: Alternate Life Form: epilithic terrestrial Ecology: Small herbs with short Ecology: Appressed low climbers on creeping fusiform tubers occurring in trees or terrestrial plants on steep banks primary forest understory, particularly (Ridley, 1925), occurring primarily in along small streams, on rocks in streams primary forest (Li, 1979; Croat & or on river banks Oohns & Hay, 1981; Grayum, loco cit.) or in late secondary Croat & Grayum, loco cit.). forest regrowth Oohns & Hay, 1981). T. Croat, 1988 33

Rbapbidopbora Principal Life Form: terrestrial Principal Life Form: hemiepiphytic Ecology: Herbs with erect stems or creeping rhizomes, occurring princi­ Alternate Life Form: pally in the understory in humid to terrestrial mOist, evergreen or occasionally decidu­ epilithic ous forest or in regrowth Oohns & Hay, Ecology: Appressed-c1imbing hemi­ 1981)j occasionally occurring on lime­ epiphytes occurring from sea level to stone, on humus deposits on limestone, 2,200 m. in humid to wet, evergreen to in peat deposits, fresh water peat­ deciduous primary forests or in re­ swamps or on volcanic soils. Though growth (Croat & Grayum, loco cit.). Van species chiefly have erect stems, some Steenis (1987) lists R. angustata Schott are epigeal, creeping over the surface of and R. beccarii Engl. as new specific the soil and becoming covered with records for the rheophytic habit. humus (Nicolson, 1969).

Aglaodorum Epipremnum Principal Life Form: Principal Life Form: aquatic hemiepiphytic Alternate Life Form: Alternate Life Form: terrestrial terrestrial epilithic Ecology: Stout rhizomatous herbs growing in tidal swamps among Nypa Ecology: Appressed-c1imbing hemi­ palms (Ridley, 1925) (Sumatra & Bor­ epiphytes, occurring principally in neo). humid primary forests or in regrowth on trees or rocks (Ridley, 1925). Tribe Homalomeneae Furtadoa Scindapsus Principal Life Form: Principal Life Form: epilithic hemiepiphytic Ecology: Rheophytes with rhizoma­ Alternate Life Form: tous stems growing on wet rocks along terrestrial streams (Hotta, 1981). epilithic Ecology: Appressed-climbers occur­ Homalomena ring principally in primary forest under­ Principal Life Form: story in humid to wet areas but also in terrestrial mixed deciduous to dry deciduous for­ ests (Hu, 1968)j less frequently in secon­ Ecology: Rhizomatous to erect short­ dary forests (van Alderwerelt van stemmed herbs occurring principally in Rosenburgh, 1922a)j often terrestrial in the undergrowth of lowland primary sandy soil when juvenile (Croat & forest (van Alderverelt van Rosenburgh, Grayum, loco cit.). 1922a, 1922bj Rataj, 1975jJohns & Hay, 1981) especially along streams (Ridley, 1925j Hu, 1968) or along edges, espe­ Subfamily Philodendroideae cially on roadbanks in semi-shade (Croat Tribe Aglaonemateae & Grayum, loco cit.). Four species are Aglaonema listed as possible rheophytes and H. 34 AROIDEANA, Vol. 11, No.3 paucinervia Ridley as a typical rheo­ Alternate Life Fonn: phyte by van Steenis ( 1981 ). terrestrial Ecology: Moderately small, thick­ Tribe Cryptocoryneae leaved helophytes (swamp plants) or a Subtribe Cryptocoryninae facultative rheophyte with stoloniferous Cryptocoryne rhizomes occurring mostly in wet places in low country and in shallow water Principal Life Fonn: along streams or on stream banks (Tri­ aquatic men, 1898; Fischer, 1931; sometimes Alternate Life Fonn: being overflooded by high water (Ma­ terrestrial nilal and Sivarajan, 1982). Van Steenis epilithic ( 1981) says l. undulata Sastry. "forms dense, submerged patches on partly Ecology: Usually small, rhizomatous submerged rock in streambed (Assam). thin-leaved herbs growing in swampy, The nine Ceylon species occur appar­ mostly open areas or along the edges of ently mostly in rivers, but do not seem streams, ditches or ponds, sometimes on confined to swift-running water." rocks at edges of streams, in gravely stream beds, in cracks of rocks along Subtribe Schismatoglottidinae streams or in densely forested areas (Ridley, 1925; Henderson, 1954; Bennet, Schis~toglotUs 1979;jacobsen, 1982); some species are Principal Life Fonn: found in the fresh water tidal zone in terrestrial coastal rivers where flowering may be Alternate Life Fonn: correlated with action of the tide Oacob­ epilithic sen, loco cit.), while others are embed­ ded in sand flats along rivers during the Ecology: Herbs with short stems or rainy season and are exposed during the stoloniferous rhizomes occurring in the dry season when they flower (Li, 1979). understory of primary forest along Eleven species are listed as 'confirmed' streams, among rocks, in damp areas or rheophytes (van Steenis, 1981) and an on well-drained slopes (Ridley, 1925), additional six species are listed as 'possi­ often forming dense colonies; sometimes ble candidates' as true rheophytes and occurring as rheophytes (Croat & others "often occur in slow or stagnant Grayum, loco cit.). Three species are water of ditches and forest pools, on listed as possible rheophytes and two as river foreshores, or in small forest rivu­ typical ones by van Steenis ( 1981 ). lets.... also certain species are confined to swift-running water and can form sub­ Piptospatha merged mats on rocky or gravely bot­ toms. Leaves occur tufted on a rhizome Principal Life Fonn: which produces runners. Plants root epilithic between rocks and boulders, in clefts Ecology: Small herbs with short and in sand; they do not occur mat­ creeping rhizomes, occurring as rheo­ rooted on rocks." phytes on rocks or in cracks of rocks along streams in forest understory (Ri­ lagenandra dley, 1925). Five species are listed by van Steenis (1981) as possibly true Principal Life Fonn: rheophytes, andP. elongata (Engl.) N.E. aquatic Br. as a true rheophyte. T. Croat, 1988 35

Hottarum "Five species, all in Sarawak. At least three taxa are rheophytes" (van Steenis, Principal Life Form: 1981). A. hansenii Bogner is listed as a terrestrial new specific record for true rheophytes Alternate Life Form: by van Steenis (1987). epilithic Ecology: Small rheophytes with short, Heteroaridarum creeping rhizome on rocks in and along Principal Life Form: streams and on nearly vertical mossy epilithic banks of streams (Bogner, 1983a; Bogner & Hotta, 1983). H. truncatum (Hotta) Alternate Life Form: Bogner & Nicolson is possibly a rheo­ terrestrial phyte, while H. lucens Bogner is a Ecology: Short-stemmed rhizomatous, confirmed "typical" rheophyte (van monotypic rheophyte occurring as an Steenis, 1981, 1987). understory herb along streams in Borneo (van Steenis, 1981). Bucephalandra

Principal Life Form: Subfamily Colocasioideae epilithic Subtribe Steudnereae Ecology: Small rheophytes growing Steudnera (especially sandstone) and in crevices, Principal Life Form: in and along forest streams (Bogner, terrestrial 1980c). True rheophyte (van Steenis, 1981). Ecology: Herbs with short ascending stems occurring in the understory in wet Phymatarum areas along streams; S. colocasiifolia K Koch occurs in taller forest from 650- Principal Life Form: 1,400 m (Hu, 1968), while S. griffithii terrestrial (Schott) Hook f. occurs in shrub forest at Ecology: Small rheophyte with a 100-500 m (Li, 1979). short, creeping rhizome growing on steep alluvium banks and on alluvium Subtribe Remusatiinae deposits on the forest floor near streams Remusatia in shady areas in the understory of primary riparian forest (Bogner, 1984). Principal Life Form: Listed as a 'typical' rheophyte, without epiphytic comment, by van Steenis (1981). Alternate Life Form: terrestrial Aridarum epilithic Principal Life Form: Ecology: Tuberous herbs occurring epilithic mostly in the understory in seasonally Alternate Life Form: dry areas where plants may lose all their terrestrial leaves during the dry season. Plants grow chiefly as epiphytes (Cooke, 1906; Craib, Ecology: Small rheophytes with short 1912; Li, 1979; Bogner, 1975; Knecht, creeping rhizomes occurring on wet 1983), but may also occur in rock rocks (especially sandstone), along and crevices (G. Thanikaimoni, pers. in shallow streams in shady forested comm.), in rocky places in the forest areas (Bogner, 1979; 1981b; 1983b). (Fischer, 1931; Hu, 1968), in the under- 36 AROIDEANA, Vol. 11, No.3 story of open forest or in shrub forest on Alternate Life Form: rocks (Li, 1979). epilithic Ecology: Rhizomatous or caulescent Gonatantbus herbs, often large, occurring principally in open or semi-open forest, or along Principal Life Form: streams in partially shaded areas or in terrestrial full sun. Two basic growth types occur: Alternate Life Form: the terrestrial species tend to be large, often solitary or in small clumps and may epilithic prefer open boggy areas Oohns & Hay, Ecology: Tuberous; occurring in 1981; Burnett, 1984); lithophytic spe­ mossy, moist evergreen forest on depos­ cies tend to be smaller, generally clus­ its of humus on trees (Li, 1979); most tered and grow in rock crevices, or over common in the rainy season (D. Ni­ humus deposits on rocks, especially colson, pers. comm.). limestone (Burnett, 1984; Croat & Grayum, loco cit.), with their stems mostly repent with only the roots cov­ Subtribe Colocasiinae ered by soil. Burnett (1984) states that Colocasia Alocasia produces corms which grow on stolons off the root system and by Principal Life Form: offshoots which emerge from the side of terrestrial the rhizome. Alternate Life Form: epilithic Subtribe Hapalininae Hapaline Ecology: Often large coarse herbs with caudex short and erect or tuberous Principal Life Form: (Engler & K Krause, 1920) to cormose terrestrial (Pate & Dixon, 1982), the majority Alternate Life Form: occurring in shady places along edges of epilithic forest, frequently along streams, often in dark humid situations below 1,300 m Ecology: H. appendiculata Ridley is a (Hu, 1968; Li, 1979) or sometimes on tuberous understory herb (Ridley, steep, rocky places (Hu, 1968). The 1908) found in humus deposits along weedier species, such as C. esculenta paths with basalt rock (Bogner, 1984); H. bentbamiana Schott occurs in open (L.) Schott, may occur in moist open dipterocarp forests (Hu, 1968). H. kerrii areas in undisturbed forest, but more Gagnepain occurs in crevices in lime­ often occur in areas along water courses, stone rock (Gagnepain, 1941). roadside ditches and in marshes (Ni­ colson in Saldanha and Nicolson, 1976); C. gigantea Hook. f. is frequent on Subfamily Lasioideae limestone outcrops in creek valleys in Tribe Lasieae the understory (Ridley, 1925; Hu, 1968; Subtribe Dracontiinae Li, 1979) but also in areas away from Cyrtosperma limestone deposits (Henderson, 1954). Principal Life Form: aquatic Alocasia Alternate Life Form: terrestrial Principal Life Form: terrestrial Ecology: Coarse, short-stemmed to tu- T. Croat, 1988 37 berous (Engl. & K Krause, 1911), usu­ places along streams (Croat & Grayum, ally solitary herbs with underground loco cit.). Engler (1911) reported it to rhizomes Oohns & Hay, 1981) occurring have a short, erect caudex, but Hay in wet areas in the understory of open ( 1988) reported the stem of Podolasia woods, in regrowth or in marshy open to be rhizomatous. areas (Ridley, 1925;Johns & Hay, 1981). In New Guinea the genus usually occurs in the lowlands and in the "Lower Subtribe Pycnospathinae Montane" zone Oohns & Hay, loco cit.). Pycnospatha Principal Life Form: Lasia terrestrial Principal Life Form: Ecology: Thberous herbs occurring in aquatic sandy loam in shady places under shrubs, trees or bamboos (Bogner, 1973a). The Alternate Life Form: tuber is subterranean, usually 10 to 12 terrestrial cm deep in the soil (Bogner, loco cit.). Ecology: Short-stemmed coarse herbs with underground rhizomes Oohns & Subfamily Aroideae Hay, 1981), usually occurring in open Tribe Thomsonieae marshes or wetlands, usually in perma­ (Amorphophalleae) nently standing water (Bennett, 1979; Amorphophallus Johns & Hay, loco cit.), in marshes, at edges of bogs, or along streams in Principal Life Form: primary or cut over forest (Hu, 1968), terrestrial sometimes in river mud, usually in tidal flats (Ridley, 1925); in ridges in rice Alternate Life Form: fields, in wet bamboo forests· or in epilithic tropical and seasonal rain forest regions Ecology: Tuberous; the majority of (Li, 1979);Johns & Hay (loc. cit.) report the species in the genus are Asian, the genus to prefer areas which are principally terrestrial but occasionally markedly to somewhat seasonal and to on rocks, especially limestone (usually be tolerant of somewhat saline situa­ with a humus covering). They may occur tions. in the understory or along the margins of primary evergreen or deciduous forest Anaphyllum and usually spend at least some time in a dormant state (e.g., A. galbra F.M. Bailey Principal Life Form: in Australia, which flowers hysteran­ terrestrial thously. Most Asian species occur in Ecology: Rhizomatous herbs in humus closed primary or secondary under­ deposits of evergreen and semiever­ growth (van Alderwerelt van green forests (Croat & Grayum, loco cit.); Rosenburgh, 1920; Hu, 1968; Johns & sometimes on wet places 0. Bogner, Hay, 1981). Most are heavily rooted in pers. comm.). soil, often associated with humus or rocks (Hu, 1968). A few species are Podolasia reported from open pastures, grassy fields (Ridley, 1925), waste places or Principal Life Form: savannas Oohns & Hay, 1981) or in areas aquatic of human habitation (Mayo, pers. Ecology: Herbs occurring in swampy comm.). 38 AROIDEANA, Vol. 11, No.3

Tribe Atherurinae Tribe Areae Pinellia Theriophonum Principal Life Form: Principal Life Form: terrestrial terrestrial Alternate Life Form: Ecology: Tuberous (Engler, 1920) or epilithic cormose herbs (Sivadasan & Nicolson, 1982) occurring in moist, shady areas on Ecology: Tuberous herbs occurring rocky, lateritic soil (Manilal & Sivarajan, principally in shady wet areas along 1982) or in grassy areas of dry country creeks or rivers, on rocks in forests, in (e.g., T. crenatum Blume in Sri Lanka) rock crevices or rocky slopes by streams (Trimen, 1898). and as forest floor herbs (Hotta, 1970; Li, 1979) but also in waste fields, roadsides and cultivated lands (Hotta, loco cit.). 'lYPhonium Principal Life Form: Tribe Pistieae (see New World) terrestrial Ecology: Tuberous (Engler, 1920) to Tribe Ariopsideae cormose (Pate & Dixon, 1982) perennial Ariopsis herbs occurring from near sea level to 4,000 m (e.g., in alpine and subalpine Principal Life Form: meadows in southwest China (Li, 1979) terrestrial and principally in shady areas in thickets Alternate Life Form: near hedges and in fence rows, open epilithic areas in shade, along streams, ponds and grassy areas (Bennet, 1979; Manilal & Ecology: Tuberous herb occurring in Sivarajan, 1982), in waste ground, along crevices or on forest floor, flowering roads (Ridley, 1925; Henderson, 1954), during the rainy season and becoming sometimes in evergreen forest, fre­ leafless during the dry season (Manilal & quently in deep humus (Hu, 1968), on Sivarajan, 1982). limestone rocks in damp areas (Ridley, loc. cit.) or in bamboo forests (Li, 1979). Tribe Arisaemateae Arisaema Sauromatum Principal Life Form: Principal Life Form: terrestrial terrestrial Ecology: Tuberous (or rarely Ecology: Tuberous; occurring in rhizomatous) herbs usually occurring in shady damp places in riverine forests, understory, in Asia (as in the New upland areas in Africa (Hepper, 1968; World), often at the base of slopes, on Mayo, 1985); in Asia, Nasir (1978) rocky slopes or in ravines (Li, 1979), reported its occurrence in the under­ occasionally in wet areas, swamps or in story as well as in sunny, open places. peat bogs; occasionally in open areas Peter (1930) found Sauromatum in near forest or in regrowth in rich soil (Li, banana fields. pers. comm.), sometimes in sunny open areas (Nasir, 1978), open steppe or Eminium (see Mediterranean Re­ subdesert (Li, loco cit.). gion) T. Croat, 1988 39

EUROPE & MEDITERRANEAN REGION pally Mediterranean or monsoon cli­ (Endemic genera only) mates with a distinct dry and wet season, growing among stones, or in sand, princi­ Subfamily Aroideae pally in open areas or in waste ground Tribe Areae (Mouterde, 1966; L. Boulos, pers. Subtribe Arinae comm.). Arum Principal Life Fonn: terrestrial Biarum Ecology: Tuberous herbs adapted pri­ Principal Life Fonn: marily to a Mediterranean climate with terrestrial hot, dry summers and cool, wet winters, Ecology: Tuberous herbs in Mediter­ but occurring much further north in ranean climates, growing in hilly areas in Europe where seasonality is in tune with fields and pastures, vineyards or Hmey normally hot, moist summers and cold fields in dry, sandy areas and among winters. In both cases, plants spend a rocks (Boissier, 1884; Mouterde, 1966). significant part of their life cycle in a Flowering occurs in the fall usually just dormant, leafless condition. Growing before the leaves emerge and the leaves under a wide variety of situations, in­ die off in late spring when the plant cluding shady, woody areas along rivers becomes dormant (Mayo, 1980). and swamps in both lowlands and up­ lands (Prime, 1960), in beech forests on limestone, as well as open bush vegeta­ Subtribe Arisarinae tion, in moist loamy soil in open country, Arisarum and in hedges (H. Riedl, pers. comm.), as Principal Life Fonn: well as in pastures and abandoned areas, terrestrial especially in deep soil with small rocks (Mouterde, 1966). Ecology: Tuberous or rhizomatous herbs in Mediterranean climates, grow­ Dracunculus ing in lanes and sheltered roadsides Principal Life Fonn: (Prime, 1960). In Israel, A. vulgare terrestrial Targ.-Tozz. occurs on the coastal plains, in the inland valleys and in mountains, Ecology: Tuberous herbs growing in growing on a wide variety of soil types shady places (Boissier, 1884), usually in with the exception of pure sand or in shrubby thickets (Hegi, 1909) in areas of Mediterranean climate. marshlands (GaliI, 1978).

Helicodiceros Subtribe Ambrosiinae Principal Life Fonn: Ambrosina terrestrial Principal Life Fonn: Ecology: Tuberous herb of Mediterra­ terrestrial nean climate; dormant during the hot Ecology: Tuberous herbs in Mediter­ dry summers. ranean climates, growing principally along coasts on north facing slopes in Eminium depressions and in sandy or rocky areas Principal Life Fonn: in "grassy vegetation, degraded forests, terrestrial hedges and especially in machia-Iike Ecology: Tuberous herbs of princi- shrubs" (Riedl, 1980). 40 AROIDEANA, Vol. 11, No. 3

APPENDIX III

GLOSSARY phytes, those which have seeds germi­ nating in the soil on the ground and later grow up the tree and frequently (al­ Life Forms ways?) lose their connection with the APPRESSED-CLIMBING An epiphytic ground. In addition hemiepiphytes show (usually hemiepiphytic) plant, which variation in the degree of attachment grows tightly appressed up the side of with the majority being "appressed­ tree trunks, cliffs or stones, typically climbers" (also sometimes referred to as with the internodes getting shorter and "root-climbers"), plants with short in­ broader in age. ternodes which are growing very slowly up their support. The second growth AQUATIC Growing wholly or partly type, featured by such species as Philo­ submerged in water for most of its life. dendron scandens K. Koch & Sellow, Wholly "submerged aquatics" are those, begin their life as appressed-climbers but like jasarum, which are continuously later become scandent or even pendent. immersed except for the inflorescence which protrudes above the water. A RHEOPHYTIC Growing along the "free-floating aquatic", like Pistia, is not edges of moving streams, either those rooted in soil and plants are largely rooted in deep soil or those occurring on above the water surface owing to the rocks. buoyancy of the leaves. "Emergent aq­ TERRESTRIAL Growing in soil, even uatics" like Urospatha and Montrichar­ rocky soil but not in swampy or inun­ dia have, in general, only the roots and dated soils. lower part of the stems beneath the water but usually will not survive long without being in standing water. Storage Organs EPILITHIC Growing on rocks, some­ CORM A swollen base of a stem en­ times in shallow deposits of soil but not closed by the dry scale-like leaves, a rooted into the ground. solid structure with distinct nodes and internodes (Hartmann & Kester, 1975); EPIPHYTIC Growing on trees and not a bulb-like fleshy stem or base of a stem; rooted into the ground; in a general a "solid" bulb Oackson, 1965); an sense often used for those growing also underground stem that "is vertically on rocks, fence posts, etc.; in the strictest compressed but expanded horizontally" sense those growing on trees only; seeds (Dodd, 1962); the corm "in dormant germinating on support, not in soil on condition carries a well-defined, apical the ground. meristem, and various forms of scar HEMIEPILITHIC Growing on rocks but tissue marking points of attachment of rooted in the soil ( constitutes previously previous leaves, inflorescences and unused term). roots" (Pate & Dixon, 1982); each growing season the apical meristem of HEMIEPIPHYTIC Growing on trees the corm produces a set of aerial leaves; but rooted into the ground; may be "a flowering stem then becomes repro­ either: 1) primary epiphytes (Putz & ductive, storage tissue arises through the Holbrook, 1986) which have seeds ger­ swelling of new nodal and internodal minating on the tree and later send roots tissue" (Pate & Dixon, loco cit.); in a to the ground, or 2) secondary epi- comparison with the tuber, Starr & T. Croat, 1988 41

Taggart (1984) define a corm as devel­ est sense) (Pate & Dixon, loco cit.). "In oping new plants from "an axillary bud one type the tubers consist of swollen, on short, thick, vertical underground underground lateral shoots of vertical or stem" whereas tubers produce new horizontal orientation, whose storage shoots "from buds on tubers (enlarged potential is increased by extension and tips of slender underground rhizomes)." thickening of existing tubers or by RHIZOME The rootstock or dorsiven­ development of new tubers" (Pate & tral stem, of root-like appearance, pros­ Dixon, loc. cit.). A "second, more trate on or underground, sending off closely-prescribed form of stem tuber is rootlets, the apex progressively sending one in which each storage unit arises up stems or leaves Oackson, 1965). separately as a highly modified swollen lateral shoot on an otherwise unswollen TUBER A modified stem which devel­ shoot system" (Pate & Dixon, loc. cit.). ops below the ground as a consequence Tubers may be perennial and added to of the swelling of the subapical portion seasonally or they may be seasonally of a stolon and subsequent accumulation replaced as in the case of Amorphophal­ of reserve materials (Hartmann & Ius. Kester, 1975). A class of storage organs divided into stem tubers and root tubers ROOT TUBER Storage organs de­ (Pate & Dixon, 1982); see respective rived from roots either ariSing on exist­ definitions. ing "true" roots or arising on "adventi­ STEM TUBER "Any globoid, thick­ tious" roots which have arisen from stem cylindrical or jointed swelling of under­ tissue as opposed to already existing ground fleshy stem tissue" (in the broad- tissue (Pate & Dixon, loc. cit.).

"Shingle" leaf of Monstera spruceana. Xanthosoma robustum Schott; caules­ cent terrestrial. 42 AROIDEANA, Vol. 11 , No.3

Stenospermation marantaefolium Hemsl.; epiphyte.

Philodendron wendlandii Schott; epiphyte. T Croat, 1988 43

Montrichardia linifera (Arruda) Schott; emergent aquatic.

Orontium aquaticum L. ; emergent aquatic. 44 AROIDEANA, Vol. 11 , No.3

Lasia spinosa Thwaites; e mergent Urospatha sagittiJolia (Rudge) Schott; aquatic. emergent aquatic.

Anthurium schlechtendalii ssp. Anthurium nizandense Matuda; epi­ schlechtendalii KUl1th; epilithic. lithic. T Croat, 1988 45

Philodendron radiatum Schott; hemiepiphyte, growing on lateral branch.

Syngonium hoffmanii Schott; hemiepiphyte appressed-c1imbing. 46 AROlDEANA, Vol. 11 , No.3

Epipremnum amplissimum Eng!.; Juvenile and adult leaf forms on hemiepiphyte appressed-climbing. Rhaphidophora pinnata.

DieJJenbachia seguine (Jacq.) Schott; Xanthosoma helleborifolium (Jacq.) caulescent terrestrial. Schott; tuberous terrestrial. T Croat, 1988 47

Philodendron rigidifolium K Krause; hemiepiphytic vine.

Anthurium hacumense Eng!.; epiphyte. 48 AROIDEANA, Vol. 11 , No. 3

Jasarum steyermarkii Bunting; submerged aquatic.

Ambrosinia bassii L.; tuberous terrestrial. Photo: J. Bogner. T. Croat, 1988 49

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