A revision of the Indian species of Oberonia (Orchidaceae) R. Ansari & N.P. Balakrishnan Botanical Survey of India, Southern Circle, Coimbatore 641 003, India Summary taxonomic of the orchid for India with 41 is Two A revision genus OberoniaLindley species presented. Oberonia bisaccata and O. new species, O. balakrishnanii and O. nayarii are established. rangannaianaare considered conspecific with O. platycaulon and O. chandrasekharanii respectively. Oberonia acaulis and O. which treated each other earlier be dis- myriantha, were as synonymous to by workers, are now proved to tinct species based on detailed study of the column. sections after the classification Seidenfaden The species are grouped under six modifying proposed by (1968) to suit the Indian plants. Dichotomous keys are provided for all taxa. The geographical distribution within the is discussed. All illustrated. of each section country species are Introduction Oberonia first described in 1830 who dedicated it The genus was by Lindley to Oberon, the mythological king of fairies. While establishing the genus, Lindley recognised 13 spe- cies of which three were from India. Subsequently, many new species were added to the genus by different workers. Wight (1851) contributed six species, all from India. In 1859 Lindley revised his first list of Oberonia species incorporating all the newly described in plants, thus increasing it to 50 numbers. Later 1888, while treating the genus for Flora of British India, Hooker f. included 41 species. Of these, 21 species were considered to within the boundaries of India. Since then of occur present a large number regional floras appeared wherein further details on the distribution of these species were made avail- able. As far the Indian of Oberonia from the local floras as species are considered, apart and works orchids of restricted such those of the few taxonomic on regions as King & Pantling (1895 and 1898), Duthie (1906), Santapau & Kapadia (1966), Abraham & Vatsala (1981), Ansari et al. (1982), Joseph (1982), Kataki (1986), etc., there is no consolidated work giv- detailed of all the Seidenfaden while the ing descriptions species. (1968) revising genus Oberoniaof MainlandAsia includedall the Indianplants known at that time; but it covers the 20 of intensive wider geographic regions. Since then, during past years explorations, many new species were added and some alien species were recorded from India. Pradhan (1979) gave a comprehensive account of the Indian species of Oberonia, but the descrip- tions were mostly adopted fromother published works and gives little importance to their Based all earlier works and Jain & Mehrotra enumerated 44 taxonomy. on records, (1984) species of Oberonia from India. Orchid Monographs 4 (1990) 1-82, figures 1-41 + plates 1-3 1 PRESENTATION, MATERIALS AND METHODS The work started with the intention make consolidated present was to an up-to-date ac- count of the Indian species of Oberonia. The herbarium specimens availablein all the major Indian herbariahave extensively been used for this work. Efforts have been madeto exam- ine pickled as well as live materials as much as possible to obtain details which will not be evident in the dried specimens. Specimens in the Kew Herbarium where the majority of the of Indian could be studied. the microfiche types plants are located, not However, and the duplicates of many of these types are available in the Indian herbaria. Although the possi- bility of error in duplicates of types are not excluded, it is only reasonable to accept them as identical with the and hence referred types they are invariably as types in the succeeding pages. Detailed descriptions of 41 species of Oberonia recognised after analytical study of spec- imens and review of literature in the of five are provided present paper. Specimens species could not be examined due to the lack of specimens in the Indian herbaria. They are listed at the end of the systematic treatment. All the intraspecific variations notedare included in the of in the of minute flower description. Range variations measurements parts are excluded of all the taken unless when this difference is by providing an average measurements re- The in the markably great. species are arranged sequence as they are numbered in the keys. The citation of minimised the synonyms are by restricting to names as they appear in the Indian works dealing with plants under the genus Oberonia, excepting for basionyms. of all the illustrations. of similar Descriptions species are supplemented by Figures parts are uniformly enlarged in all the species so that the size differencescan readily be recog- nised. By attempting to do this two extremeties in the size of the figures have appeared, but the same magnification of all parts is considered advantageous for a comparative analysis of the plants. Data for phenology and altitude are taken from collector's notes on the herbarium sheets. But in certain this is cases adjusted based on earlier published works, especially when the collections are insufficient. Distribution of each taxon is summarised after its description. All specimens examined(microfiche excluded) have been listed alphabetically by local- ity and then by collector at the end of each species. The letters given in brackets after each indicate the specimen acronyms of herbaria where it is housed (for abbreviationsof the her- under baria, see Acknowledgements). Whenthe specimen cited is a type (or a duplicate of it) this is specified after the relevant herbarium. of certain Important aspects regarding taxonomy, nomenclature, distribution, etc. spe- cies discussed under the are briefly corresponding taxon, wherever it is foundnecessary. Some literature which consulted the of this important was during course study but is some- times not cited in the text, is listed at the end. MORPHOLOGICAL CONSIDERATIONS - Habit All of Oberonia are herbaceous The erect species epiphytes. plants may be or pendulous, but this character being not constant is not of any specific significance. Stem - Oberonias, in general, are acaulescent plants with a group of distichous leaves from the base. A for caulescent arising tendency nature can be noted in certain species by the of but this often elongation some upper internodes, feature varies even within the same 2 Orchid Monographs 4 (1990) species. However, this elongation is constant and common to all the internodes in O. falcata and O. mannii. It can thus be concluded that the caulescent nature is of little value in the major grouping, but can be used as a minor character for delimiting species. Leaves - The laterally compressed leaves in distichous arrangement forms the most obvious feature of the in of section which readily diagnostic genus excepting plants I are unique in having more or less terete leaves. In plants of section I to IV, an articulation can be seen near the base of each leaf and in such cases the leaves are deciduous. Plants of the other sections have persistent leaves. - forms of Scape Two scapes can be distinguished among the plants of Oberonia. It may be either terete (or indistinctly so), or flattened and winged laterally with the reduced uppermost leafoften carried along with it to a certain distance. Spike - The spike is thick and fleshy with closely adpressed flowers in O. pachyrachis, whereas in the other species it is rather thin bearing somewhat loosely arranged flowers. The aestivation of flowers on the spike may be spiral, verticillate or scattered. In certain species of section III, a definiteportion at the apex ofthe spike will always remain sterile. However, in O. platycaulon the spike is dimorphous, being with or without a sterile por- tion. Flowers - In Oberonia the flowers are minute. The largest flowers noted are in O. ana- malayana measuring up to 5.25 mm long and 2 mm across. Flowers may be sessile or pedi- celled, but this cannot be distinguished with certainty in all cases since the pedicel is con- tinuous with the inferiorovary. Hence this is a fragile character for species delimitation. Bracts — Each flower is supported by a bract. In certain instances, a single bract may bear two or three flowers in its axil, but this is not consistent in any species. In general, bracts are of littletaxonomic value. Sepals - Although the size, shape and margins of sepals are notably variable, their ori- entation in floweroften forms a useful supplementary character for species differentiation. Petals - The petals often exhibit specific consistency in their shape, margins, orienta- useful for initial tion, etc. In many cases they are determination. Lip - Although minor intraspecific variations are not uncommon, the lip is considered to of valuable for be one the most structures delimiting species. A great variation of lip forms is in the with Hence, in correlation with other present genus, specific consistency. sup- offer porting characters, lips valuable clues for drawing up the linesof affinities withinthe genus. Disc - The disc on the lip may be indistinct, cushion-like, concave, saccate or tubular and its in is considered A form of is use determining species great. peculiar disc present in the lip of O. ensiformis where the lateral lobes are separated from the midlobe by an elon- gated mesochil. - Column The column is the specialized reproductive structure, combining androecium and gynoecium, peculiar to Orchidaceae. Even though it has largely been used for classify- ing orchids at the generic level, its use in infrageneric categories was believed to be meagre. In Oberonia the column is minute and hence remained a very structure neglected or insuf- studied in of the In work attention is this ficiently most cases. the present special paid to structure and in many cases it is found to be of great value in delimiting closely allied and doubtfulspecies. The column, in general, is a cylindric or globose structure at the centre of the flower, bearing at the tip the stigma and the pollinia bearing cavity (clinandrium).