Gardens’ Bulletin Singapore 62 (2): 277–289. 2011 277 Studies on Homalomeneae (Araceae) of Peninsular Malaysia II: An historical and taxonomic review of the genus Homalomena (excluding Chamaecladon) Kiaw Kiaw Ng, P.C. Boyce1 and S. Othman Pusat Pengajian Sains Kajihayat (School of Biological Sciences), Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia 1 phymatarum@googlemail.com (corresponding author) ABSTRACT. An historical and taxonomic review of Homalomena (excluding species assigned to the Chamaecladon Supergroup sensu Boyce & Wong) for Peninsular Malaysia is presented. Five species are recognised of which one, H. truncata (Schott) Hook.f. represents a new species record for the Peninsula. Keys to the Peninsular Malaysian Supergroups and species, and a taxonomic conspectus, are provided. Three species are illustrated from living plants, and H. wallichii from the type specimen. Keywords. Araceae, Homalomena, Supergroup, Peninsular Malaysia Introduction Recent publications on Asian Homalomena have focussed on Papuasia (Hay 1999, Herscovitch & Hay 2003) and East Sunda (Hay & Herscovitch 2002; Boyce & Wong 2008, 2009; Boyce, Wong & Fasihuddin 2010). Until recently, apart from ad hoc descriptions of new taxa (Baharuddin & Boyce 2005, 2009), little attention has been paid to the genus in Peninsular Malaysia. Apart from Ridley’s adequate but now outdated account (1925), the only complete review is that of Furtado (1939), an account marred not least by poor and often confused species’ delimitation. Hay (1999) provided a concise taxonomic and nomenclatural historical review of Homalomena in Papuasia. More recently, Boyce & Wong (2008) and Ng et al. (in press) proposed and elaborated informal supergoups and species complexes as a tool to aid taxonomic study of this speciose and taxonomically ill-understood genus. This is a precursory account intended to provide a taxonomically and nomenclaturally stable framework for the Peninsular Malaysian Homalomena species belonging to the Homalomena and Cyrtocladon Supergroups (sensu Boyce & Wong 2008). From this platform it is intended to tackle the taxonomy of the numerous undescribed Peninsular Malaysian species. Species assigned to the Chamaecladon Supergroup (sensu Boyce & Wong 2008), which account for the majority of the described species in the Peninsula, present considerable taxonomic and nomenclatural problems and will be the focus of a future study. 278 Gard. Bull. Singapore 62 (2) 2011 History of the genus in Peninsular Malaysia The irst Homalomena species pertinent to Peninsular Malaysia appeared in No.1 of Jack’s Descriptions of Malayan Plants (Jack 1820) as Calla angustifolia Jack and C. humilis Jack. Both are now treated as synonyms of Homalomena humilis (Jack) Hook.f. (Chamaecladon Supergroup – see Boyce & Wong 2008) and fall outside the scope of this paper. Grifith (1851a) posthumously established new four species, three in Homalomena, and one in a new genus, Cyrtocladon Griff. (see also Grifith 1851b). Two of Grifith’s Homalomena species (H. minor Griff. and H. major Griff.), were based upon incomplete material from the same locality (Pulau Besar, Melaka), and since publication have been treated as, and here remain, doubtful. Grifith’s third species, H. rostrata Griff., with which Cyrtocladon sanguinolentum Griff. is conspeciic, is a highly variable colonial helophyte widespread in Sunda and with an extensive synonymy. It has been treated in an account of helophytic Homalomena (Wong, Boyce & Fasihuddin 2011). Schott (1856) recognised nine species for Homalomena, with only those described by Grifith listed for the Peninsula. Schott retained Grifith’s Cyrtocladon, but made no mention of the species assigned by Jack to Calla . Schott (1860) recognized 12 species for Homalomena, and a further nine in Chamaecladon, which he treated as a genus, and no longer accepted Cyrtocladon. He listed four Homalomena species for the Peninsula, viz. Grifith’s three species (H. major, H. minor, H. rostrata), and added H. wallichii Schott, which he had described from Pinang the previous year (Schott 1859). Engler (1879) recognized 17 species for Homalomena, but made no increase to the number, nor altered the status, of species in the Peninsula from that of Schott (1860). Engler treated Chamaecladon as a genus, with 13 species. Hooker (1893) increased to 23 the number of species in Homalomena, with 17 recorded for the Peninsula and Singapore, of which 12 are in Chamaecladon, treated as a section. Of the other ive species, Hooker erroneously considered Javan H. coerulescens Jungh. ex Schott to be present in the Peninsula and within it included H. major, H, minor, and H. wallichii as synonyms. Notwithstanding that H. minor and H. major (Grifith 1851) have priority over H. coerulescens (Schott 1856), virtually all material determined as H. coerulescens by Hooker represents novel taxa. The remaining species comprise H. paludosa Hook.f., H. rostrata, and H. sagittifolia, now treated as conspeciic (= H. rostrata), and Peninsular Malaysian and southern Thai H. pontederiifolia Griff. ex Hook.f. Ridley’s precursory accounts for the Peninsula (Ridley 1902, 1907) listed 21 species with 17, including H. mixta Ridl. (= Furtadoa mixta (Ridl.) M.Hotta – see Hotta 1985), treated as belonging to sect. Chamaecladon. The taxonomy of Ridley’s 1907 treatment follows that of Hooker (1893) with the exceptions that H. propinqua Schott was added to the synonymy of H. sagittifolia, and H. pontederiifolia is treated as a synonym of H. coerulescens. Ridley (1907) made no mention of H. ridleyana Engl. (Engler 1907), having presumably not yet seen the publication. Engler (1912) remains the only complete revision of Homalomena to date. He recognised 80 species, of which 37 are in sect. Chamaecladon. Excluding those assigned to Chamaecladon, only six species are recorded for Peninsular Malaysia. One new species, H. curvata Engl., is added but otherwise the account generally follows Historical and taxonomic review of Homalomena 279 those of Hooker (1893) and Ridley (1907) in listing H. coerulescens (including H. major, H, minor, and H. wallichii as synonyms), and maintaining H. paludosa, H. rostrata, and H. sagittifolia as distinct species. Engler resurrected H. pontederiifolia, and treated H. ridleyana as a synonym of H. paludosa. Ridley (1925) treated 24 species, with 20 species in sect. Chamaecladon. The taxonomy is otherwise as that of Engler (1912) with the exception that Ridley reduced H. curvata to H. coerulescens, and combined H. pontederiifolia as a variety of H. coerulescens. Homalomena deltoidea Hook.f. (= H. grifithii (Schott) Hook.f.) is misplaced in sect. Homalomena (‘Eu-Homalomena’). Furtado (1939) recognized 58 species, of which 35 were placed in sect. Chamaecladon, four in Homalomena (‘Eu-Homalomena’), and 18 in Cyrtocladon, newly treated as a section. Excluding those assigned to Chamaecladon, Furtado listed four species for the Peninsula, of which three (H. propinqua, H. rostrata, and H. sagittifolia) are now treated as a single species: H. rostrata. Furtado attempted to update Ridley (1925) and Engler (1912), in particular to deal with confusion surrounding early names published for what is now Indonesia, but in fact his account created more confusion than it resolved. The biggest problem is Furtado’s hopelessly muddled treatment of Javan H. rubra Hassk., a species absent from the Peninsula, but into which Furtado subsumed ive Peninsular taxa: H. curvata, H. major, H. minor, H. pontederiifolia, and H. wallichii. Conspectus of Homalomena (excluding the Chamaecladon Supergroup) in Peninsular Malaysia Homalomena curvata Engl., Planzenr., 55(IV.23Da): 53 (1912). TYPE: Malaysia, Melaka, (“Malakka”), Wells Hill, bei Kuala Lumpur (but see below), 50 m, Feb 1906, A. Engler (Reise nach Java und Brit. Indien) n.5292 (holo B!). (Fig. 1) Notes: Engler’s type locality data are confusing. While Wells Hill (modern Bukit Cina) is indeed in Melaka, it lies some 120 km SE of Kuala Lumpur. It is probable that Engler’s labeling led Ridley to not recognise H. curvata as a valid species, since Ridley appears to have not seen the type and instead based his decision on his collection (cited by Ridley 1925) of a different species from Weld’s Hill (now renamed Bukit Nanas, adjacent to Bukit Mahkamah), Kuala Lumpur. It seems that Ridley confounded Weld’s Hill, Kuala Lumpur with Wells Hill, Melaka. Ironically, Ridley’s Weld’s Hill collection almost certainly represents an undescribed species. However, the material is both inadequate and in a poor state of preservation, and thus unsuitable from which to prepare a description. A good portion of Bukit Nanas is in the Bukit Nanas Forest Reserve where some degree of natural vegetation still exists. This is the same hill as St John’s Institution, Bukit Nanas Convent, and the imposing KL Tower. On the other hand, the present Bukit Mahkamah used to be called Court Hill (Mahkamah = Court) because the former High Court Building was situated there (precursor to the Menara Maybank). There remains a possibility Ridley’s unnamed taxon may have persisted. Bukit Nanas and Bukit Mahkamah are on opposite sides of a road that used to be called Weld Road (now Jalan Raja Chulan). 280 Gard. Bull. Singapore 62 (2) 2011 Fig. 1. Homalomena curvata Engl. A. Plants in habitat. B. Detail of emerging inlorescences. C. Developing infructescences. D. Detail of abaxial leaf surface showing the diagnostic striate pellucid secretory canals. E. Holotype (B). A–D from Ng et al. AR-3052. Photo credits: P.C. Boyce. E from A. Engler 5292. Photo credit: Botanic Garden and Botanical Museum BerlinDahlem, Freie Universität Berlin. Used with permission. Historical and taxonomic review of Homalomena 281 An alternative interpretation is that Engler only wrote “Malakka” because there was no real country called Malaysia then, and he was in fact referring to Weld’s Hill near Kuala Lumpur (and then misspelling that as ‘Wells Hill’). If that were the case, the locality formerly called Weld’s Hill (now Bukit Nanas) used to accommodate at least two Homalomena spp., not impossible by lowland humid forest and Homalomena standards. Possible corroboration from Melaka and Bukit Nanas material may become available. That no one after Engler recognised H. curvata as a distinct species is remarkable. Critical examination of the holotype (B), and the irst author’s recent new collections from the Jerantut Krau Wildlife Centre, Pahang (Ng AR-3052 & Ng AR-3053) leave us in no doubt that the conspicuous striate pellucid secretory canals running parallel to the primary lateral veins on the abaxial side of the leaf blade make H. curvata a species wholly distinct from any other yet described in Peninsular Malaysia. Homalomena curvata appears to be an outlying representative of a species complex otherwise centred on N. Borneo, and from where at least a dozen species, in the main associated with limestone, await description. Homalomena pontederiifolia Griff. ex Hook.f., Fl. Brit. Ind. 6: 533 (1893). LECTOTYPE (selected here): Malaysia, Melaka, Air Panas (‘Ayer Punus’) – see below, W.Grifith 5964 (lecto K!). (Fig. 2) Notes: As treated here Homalomena pontederiifolia is the commonest of the larger species in Peninsular Malaysia, but paradoxically poorly represented in herbaria, possibly because its large and bulky nature dissuades collection. It is very likely that more extensive collecting and exhaustive study will reveal that the species comprises several distinct taxa. Hooker cites three syntypes, of which Grifith’s collection, here selected as lectotype, is the only one that completely matches the protologue. Grifith’s locality (‘Ayer Punus’) is almost certainly the same as modern Taman Rekreasi Air Panas Jasin, Melaka; the specimen was likely collected not long before Grifith’s death from a parasitic liver disease in Melaka in February 1845, shortly before his 35th birthday. Of the other syntypes cited by Hooker, D.F.A. Hervey s.n (K!), although sterile, represents an undescribed species of the Hanneae Complex (see Ng et al., in press), based on the marcescent margin of the petiolar sheath, and leaf blades with scattered glandular punctuations (the latter admittedly only faintly discernible). Fr B. Scortechini s.n. (CAL! K!) approaches H. pontederiifolia, but the inlorescences are only half the typical length for the species and the material is otherwise too depauperate to be unequivocally placed taxonomically. Homalomena rostrata Griff., Not. Pl. Asiat. 3: 154 (1851) [‘roshalum’]. TYPE: Malaysia, Melaka, W. Grifith 5989 (holo K!). Cyrtocladon sanguinolentum Griff., Not. Pl. Asiat. 3: 147 (1851); Chamaecladon sanguinolentum (Griff.) Schott, Prodr. Syst. Aroid.: 316 (1860). TYPE: Malaysia, Melaka, W. Grifith 5990 (holo K!). 282 Gard. Bull. Singapore 62 (2) 2011 Fig. 2. Homalomena pontederiifolia Griff. ex Hook.f. A. Plant in cultivation, ex Johor, Malaysia. B. Inlorescence at female anthesis. C. Inlorescence at female anthesis, spathe artiicially removed. Scale bar = 2 cm. D. Detail of staminate lower zone. Note the well-deined lowers each with 4–6 anthers and large synconnectives. E. Detail of pistillate lower zone and lower portion of staminate zone. The lowermost staminate lowers are sterile (staminodes). Note that interpistillar staminodes equal the pistils in length. A–E from Boyce AR-2355. Photo credits: P.C. Boyce. Historical and taxonomic review of Homalomena 283 Homalomena sagittifolia Jungh. ex Schott, Prodr. Syst. Aroid.: 311 (1860). TYPE: Malaysia, Sabah, Labuan, Motley s.n. (holo K!); epitype (see Wong et al., 2011): Indonesia, Java, F.F.W. Junghuhn s.n. W†; Schott Ic., no. 2111 (W!). – Fiche no. 44: a4 in the microiche edition. Homalomena miqueliana Schott, Ann. Mus. Bot. Lugduno-Batavi 1: 126 (1863). TYPE: Indonesia: Borneo, Kalimantan, P.W. Korthals s.n. (holo L!). Homalomena propinqua Schott, Ann. Mus. Bot. Lugduno-Batavi 1: 280 (1864). TYPE: Indonesia, Kalimantan, Kalimantan Selatan, Mt. Gintang, P.W. Korthals s.n. (holo L!). Homalomena beccariana Engl., Bull. Soc. Tosc. Ortic. 4: 296 (1879). TYPE: Malaysia, Sarawak, Kuching, Jul 1865, O. Beccari P.B. 260 (holo FI-B!). Homalomena paludosa Hook.f., Fl. Brit. India 6: 531 (1893). LECTOTYPE: Malaysia, Perak, Larut, H.H. Kunstler (‘Dr King’s Collector’) 3082 (lecto K! isolecto CAL, SING!). Homalomena sagittifolia var. pontederiifolia Ridl., J. Straits Branch Roy. Asiat. Soc. 44: 172 (1905). – Homalomena ridleyana Engl., Bot. Jahrb. Syst. 37: 123 (1907). TYPE: Malaysia, Borneo, Sarawak, Kuching, E. Bartlett & G.D. Haviland 3134 (holo SING!). Homalomena teysmannii Engl., Planzenr., IV, 23Da: 68 (1912). TYPE: Indonesia, Sumatera, Bangka Island, J.E. Teijsmann 3227 (holo B! iso BO!). Homalomena raapii Engl. Planzenr., IV, 23Da: 73 (1912). LECTOTYPE (see Wong et al., 2011): Indonesia, Sumatera, H. Raap 235 (lecto BO!). Homalomena triangularis Alderw., Bull. Jard. Bot. Buitenzorg, III, 4: 181 (1922). TYPE: Indonesia, Sumatera, Deli, 27 Jul 1915, J.A. Lörzing 4071 (holo BO!). Homalomena sagittifolia var. sumatrana Alderw., Bull. Jard. Bot. Buitenzorg, III, 4: 192 (1922). LECTOTYPE (see Wong et al., 2011): Indonesia, Sumatera, Ophir, Taloe, 10 Apr 1917, H.A.B. Bünnemeijer 129 (lecto BO!). Homalomena ensiformis Alderw., Bull. Jard. Bot. Buitenzorg, III, 4: 335 (1922). TYPE: Indonesia, Kalimantan, J.G. Hallier 1465 (holo BO! iso L!). Homalomena miqueliana var. truella Alderw., Bull. Jard. Bot. Buitenzorg, III, 4: 336 (1922). TYPE: Indonesia, Sumatera, Riau Archipelago, Ampoelai, Pulau Bintang, 14 Jun 1919, H.A.B. Bünnemeijer 6200 (holo BO! iso L!). Homalomena sagittifolia var. angustifolia Furtado, Gard. Bull. Straits Settlem. 10: 228 (1939). LECTOTYPE (see Wong et al., 2011): Malaysia, Johore, Mt Austin, H.N. Ridley 12018 (lecto SING! isolecto K!). 284 Gard. Bull. Singapore 62 (2) 2011 Notes: See Wong et al. (2011) for a detailed discussion and illustrations of this species. Homalomena truncata (Schott) Hook.f., Fl. Brit. India 6: 535 (1893). – Chamaecladon truncatum Schott, Bonplandia (Hannover) 6: (1858). LECTOTYPE selected here: Myanmar, Mergui, W. Grifith s.n. (lecto K!). (Fig. 3) Notes: Schott (1858) cited no material for Chamaecladon truncatum, although the protologue is explicitly prepared from preserved rather than living plants. Schott’s description in the Prodromus (Schott 1860) is largely identical to that in Bonplandia, and further cites two specimens, from Mergui and Tenasserim, both extant in Kew (K). That chosen as lectotype is autographed by Schott, and is also the better preserved of the two. Schott’s placement of H. truncatum in Chamaecladon is at odds with the morphology of the interpistillar staminodes (exceeding the associated pistils), and the staminate lowers comprising four stamens and synconnectives. It seems likely that Schott regarded the rather small, unconstricted spathes as more pertinent to placement than the iner loral details. This represents a new record for the Peninsula. Homalomena truncata is a common species in the north of Peninsular Malaysia occurring in subhumid to humid forest, often, but not exclusively, associated with limestone. Homalomena wallichii Schott, Bonplandia (Hannover) 7(3): 30 (1859). TYPE: Malaysia, Pulau Pinang, Aug 1822, N. Wallich EIC 8951 (holo K-W!). (Fig. 4) Notes: Much as with H. curvata, H. wallichii was reduced to synonymy virtually the moment it was published, and as with H. curvata one can only speculate as to how such a distinctive species could have been so treated. The habit of the sterile plant – with long-petiolate pendent leaf blades (leaf tip directed downwards) recalls that of an Alocasia – while fertile plants are unmistakable by the exceptionally long peduncle, with the inlorescence often equalling the preceding petiole. Homalomena wallichii is very uncommon in the wild, and furthermore appears to be restricted to a very small area of Pinang, fortunately within the Taman Negara Pulau Pinang (“Muka Head N.P.”) Inadequately known species Homalomena major Griff. (‘majus’), Notul. Pl. Asiat. 3: 153 (1851). TYPE: Malaysia, Melaka, Pulau Besar [‘Pulo Bissar in Sylvis collinis’], Sep 1842. W. Grifith 6011 (K). Homalomena minor Griff. (`minus’), Notul. Pl. Asiat. 3: 152 (1851). TYPE: Malaysia, Melaka, Pulau Besar [‘Pulo Bissar in Sylvis collinis’], Sep 1842. W. Grifith 5961 (K). Notes: These collections are almost certainly the same species, but the material is inadequate, seemingly preserved late in anthesis (thus many important loral characters probably already lost) and now too fragile to enable dissection to assign them to any known plant. A further problem is that Pulau Besar is now much degraded, although Historical and taxonomic review of Homalomena 285 Fig. 3. Homalomena truncata (Schott) Hook.f., A. Plant in cultivation, ex Kedah, Malaysia. B. Emerging inlorescences. C. Inlorescence at female anthesis, spathe artiicially removed. Scale bar = 1 cm. D. Detail of staminate lower zone. Note the well-deined lowers each with 4 anthers and small synconnectives. E. Detail of pistillate lower zone and lower portion of staminate zone. The lowermost staminate lowers are sterile (staminodes). Note that interpistillar staminodes subequal the pistils in length. A–E from Boyce AR-2354. Photo credits: P.C. Boyce. 286 Gard. Bull. Singapore 62 (2) 2011 Fig. 4. Homalomena wallichii Schott. Holotype, K-W. Photo credit: The Trustees, Royal Botanic Gardens, Kew. Used with permission. Historical and taxonomic review of Homalomena 287 certainly an attempt to re-collect at the site must be attempted before these names are relegated to “nomina obscura”. Key 1. Peninsular Malaysian Homalomena Supergroups 1a. Spathe at most 1.5cm long, often much less, without a constriction. Staminate lowers each comprising 2–3 stamens not united by a common connective. Interpistillar staminodes shorter than the pistils. (Mostly small plants and often rheophytic.) ............................................................. Chamaecladon Supergroup 1b. Spathe more than 2.5 cm long, often much longer, with or without a constriction. Staminate lowers each comprising 3–4 (rarely 5–6, very rarely 1) stamens united by a conspicuous common connective. Interpistillar staminodes equaling or slightly exceeding the pistils. (Mostly medium to large plants and in the Peninsula wholly mesophytic.) ............................................................................................ 2 2a. Spathe not divided into a lower and upper portion by a constriction. Inlorescence movement during anthesis comprising simple gaping and closing of the spathe limb, with virtually no spadix movement ............................................................... ................................................................. Homalomena Supergroup (see Key 2) 2b. Spathe divided by a moderate to pronounced constriction into a well-deined upper (limb) and a lower portion. Inlorescences during anthesis with complex spathe and spadix movements and often spadix elongation .................................... .................................................................. Cyrtocladon Supergroup (see Key 3) Key 2. Peninsular Malaysian Homalomena 1a. Flowering plants large, often exceeding 1 m tall. Spathe 8-14 cm long; spadix 7–13 cm long ...................................................................................... H. pontederiifolia 1b. Flowering plants of medium size, seldom exceeding 40 cm tall. Spathe 4–6 cm long; spadix 5–6.5 cm long ................................................................................. 2 2a. Leaf blade abaxially with conspicuous striate pellucid secretory canals running parallel to the primary lateral veins. (S Peninsula as far north as S Pahang.) ....... .............................................................................................................. H. curvata 2b. Leaf blade abaxially without striate pellucid secretory canals. (Kedah, Perlis.) ....... ............................................................................................................ H. truncata Key 3. Peninsular Malaysian Cyrtocladon 1a. Colonial helophytes, almost always in peatswamp or the wet facies of kerangas (kerapah) forest and always in inundated situations ............................H. rostrata 1b. Solitary to clumping forest mesophytes in moist well-drained situations in lowland perhumid mixed dipterocarp forest ...................................... (numerous sp. nov.) 288 Gard. Bull. Singapore 62 (2) 2011 ACKNOWLEDGEMENTS. The irst author’s research and ieldwork in Peninsular Malaysia was supported by a Research University Grant 1001/PBIOLOGI/811132 from the Universiti Sains Malaysia (USM), Penang, Malaysia. The irst author is also grateful for inancial support supplied by a USM Fellowship. The second author wishes to extend thanks to the Keeper and staff of the Herbarium, Royal Botanic Gardens, Kew, for graciously allowing access to their collections and for permission to reproduce in this paper images of pertinent specimens. We wish to express our gratitude to Dr Wong Khoon Meng (SING) for very useful information regarding Weld’s Hill, and the implications for yet further novel taxa, reproduced above almost verbatim. References Baharuddin, S. & Boyce, P.C. 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