Recircumscription of the monocotyledonous family Petrosaviaceae to include Japonolirion

Most systematists have favored placing Petrosaviaceae close to the Triuridaceae (formerly positioned within Alismatidae) by focusing on the mycoheterotrophic habit and nearly free carpels of Petrosaviaceae. Others have favored a position near the melanthioid lilies, perhaps serving as a linking-family to the Triuridaceae. We discuss the results of recently published, independent, and combined DNA sequence analyses that indicate a strongly supported sister relationship betweenPetrosavia (Petrosaviaceae) andJaponolirion (Japonoliriaceae). Molecular data show no connection of these genera to the Alismatales (including Tofieldiaceae), the Melanthiaceae s. str., the Liliales, or the Triuridaceae (now in Pandanales), although there are morphological similarities to each of these groups. A relationship to the Pandanales has been indicated in some molecular analyses, but this is not supported by bootstrap/jackknife analyses or by most morphological characters. BothPetrosavia andJaponolirion are native to high-evelation habitats and have bracteate racemes, pedicellate flowers, six persistent tepals, septal nectaries, three nearly distinct carpels, simultaneous microsporogenesis, monosulcate pollen, and follicular fruits. Outside of the Alismatales, no other monocotyledons share this combination of features. We therefore suggest that the Petrosaviaceae be re-circumscribed to includeJaponolirion. If the family's isolated position among the monocot orders continues to be found in phylogenetic studies, then recognition of the already published order Petrosaviales would be appropriate.     

Gymnogrammitis dareiformis is a polygrammoid fern (Polypodiaceae) – Resolving an apparent conflict between morphological and molecular data

 Maximum parsimony and maximum likelihood analyses of the combined data sets of two chloroplast genes, rbcL and rps4, demonstrate that nk;the monotypic genus Gymnogrammitis is part of the polygrammoid clade (Polypodiaceae + Grammitidaceae), and not the Davalliaceae as proposed in most studies. The genus forms a clade together with two Asiatic genera of the Polypodiaceae, Arthromeris and Selliguea. These last two genera have either simple or once-pinnate leaves, whereas Gymnogrammitis has highly divided (3- to 4-pinnate) blades. Two characters of this genus, the basic chromosome number of x=36 and the absence of indusia, support a relationship with the Polypodiaceae. Neither feature is found within Davalliaceae. Three morphological characters support the placement of Gymnogrammitis within the selligueoid lineage of Polypodiaceae: spores with a thick perine extending in microspines, sclerenchymatous strands in the rhizome, and non-clathrate rhizome scales. These results demonstrate that molecular and morphological data are phylogenetically congruent with the exception of blade dissection. Our study clearly shows the pitfalls of classifications based on single characters, and illustrates the importance of phylogenetic assessment of all taxonomic conclusions. Received November 22, 2001; accepted May 21, 2002 Published online: November 14, 2002 Addresses of the authors: Harald Schneider (e-mail: hschneid@duke.edu), Department of Biology, Duke University, Durham, North Carolina, 27708, USA; Current address: Albrecht-von-Haller Institut für Pflanzenwissenschaften der Universit?t G?ttingen, Abteilung Systematische Botanik, Untere Karspüle 2, D-37073 G?ttingen, Germany. Alan R. Smith, Ray Cranfill, University Herbarium, University of California, Berkeley, California 94720-2465, USA. Christopher H. Haufler, Terri Hildebrand, Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA. Tom A. Ranker, University Museum and Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, Colorado 80309, USA.     

Triuridaceae fossil flowers from the Upper Cretaceous of New Jersey

We report here on a series of fossil flowers exhibiting a mosaic of characters present in the extant monocot family Triuridaceae. Phylogenetic analyses of morphological data from a broad sample of extant monocots confirm the affinities of the fossils with modern Triuridaceae. The fossil flowers were collected from outcrops of the Raritan Formation (Upper Cretaceous, ～90 million years before present), New Jersey, USA. These are the oldest known unequivocal monocot flowers. Because other reports of "earliest" monocots are all based on equivocal character suites and/or ambiguously preserved fossil material, the Triuridaceae fossils reported here should also be considered as the oldest unequivocal fossil monocots. Flowers are minute and unisexual (only male flowers are known); the perianth is composed of six tepals, lacking stomata. The unicyclic androecium is of three stamens with dithecal, monosporangiate, extrorse anthers that open by longitudinal slits. The endothecium has U-shaped type thickenings. Pollen grains are monosulcate. The triurid fossil flowers can be separated into three distinctive species. On the basis of phylogenetic analyses of morphological characters, the fossil taxa nest within the completely saprophytic achlorophyllous Triuridaceae supporting the interpretation that the extinct plants were also achlorophyllous and saprophytic. If so, this represents the earliest known fossil occurrence of the saprophytic/mycotrophic habit in angiosperms.     

A bi-organellar phylogenomic study of Pandanales: inference of higher-order relationships and unusual rate-variation patterns

We used a bi-organellar phylogenomic approach to address higher-order relationships in Pandanales, including the first molecular phylogenetic study of the panama-hat family, Cyclanthaceae. Our genus-level study of plastid and mitochondrial gene sets includes a comprehensive sampling of photosynthetic lineages across the order, and provides a framework for investigating clade ages, biogeographic hypotheses and organellar molecular evolution. Using multiple inference methods and both organellar genomes, we recovered mostly congruent and strongly supported relationships within and between families, including the placement of fully mycoheterotrophic Triuridaceae. Cyclanthaceae and Pandanaceae plastomes have slow substitution rates, contributing to weakly supported plastid-based relationships in Cyclanthaceae. While generally slowly evolving, mitochondrial genomes exhibit sporadic rate elevation across the order. However, we infer well-supported relationships even for slower evolving mitochondrial lineages in Cyclanthaceae. Clade age estimates across photosynthetic lineages are largely consistent with previous studies, are well correlated between the two organellar genomes (with slightly younger inferences from mitochondrial data), and support several biogeographic hypotheses. We show that rapidly evolving non-photosynthetic lineages may bias age estimates upwards at neighbouring photosynthetic nodes, even using a relaxed clock model. Finally, we uncovered new genome structural variants in photosynthetic taxa at plastid inverted repeat boundaries that show promise as interfamilial phylogenetic markers.     

Hybridization between the peat mosses, Sphagnum capillifolium and S. quinquefarium (Sphagnaceae, Bryophyta) as inferred by morphological characters and isozyme markers

 Isozyme markers and morphological characters were studied in four populations of Sphagnum capillifolium and S. quinquefarium. Recombinant plants were found in three populations, where the two species occur sympatrically. All recombinants possessed different haplotypes and combinations of morphological characters, which show that they are results of independent hybridization events. Strongly male-biased sex ratios were found for Sphagnum capillifolium in all populations where it grew sympatrically with S. quinquefarium. Most of the recombinants were also male fertile. These observations suggest that S. quinquefarium is the female parent in the primary crosses and in subsequent backcrosses. Received September 3, 2001; accepted March 16, 2002 Published online: November 7, 2002 Addresses of the authors: Nils Cronberg (e-mail: Nils.Cronberg@sysbot.lu.se), Department of Systematic Botany, Lund University, S?lvegatan 37, SE-223 62 Lund, Sweden. Rayna Natcheva (e-mail: renimoss@iph.bio.bas.bg), Institute of Botany, Bulgarian Academy of Sciences, 23 Acad. G. Bonchev Str., 1113 Sofia, Bulgaria.     

Molecular differentiation of two vicariant neotropical tree species, Plathymenia foliolosa and P. reticulata (Mimosoideae), inferred using RAPD markers

 Plathymenia foliolosa and P. reticulata are two tropical tree species economically important for their high quality wood. P. foliolosa occurs mainly in areas of Atlantic Forest (a tropical forest) whereas P. reticulata occurs mainly in the Cerrado region (a savanna vegetation), both Brazilian biomes classified as hotspots for conservation priorities. In the present study RAPD markers were used to differentiate P. foliolosa from the vicariant species P. reticulata. Using 10 random primers it was possible to obtain 84 markers, of which 22 (26.2%) were present in just one of the two species. Nine of the ten primers were successful in discriminating between the species through the detection of diagnostic markers or band frequency differences. One of the populations of P. foliolosa, located in a region where the two species co-occur, presented several markers that were characteristic of P. reticulata, suggesting the occurrence of gene flow between the two species. Received September 3, 2001; accepted August 19, 2002 Published online: November 22, 2002 Addresses of the authors: Daniela Rodrigues Lacerda (dlacerda@dedalus.lcc.ufmg.br), Maria Bernadete Lovato (lovatomb@icb.ufmg.br), Maria Dolores Porto Acedo (acedomd@icb.ufmg.br), Dept. Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, CP: 486, Belo Horizonte, MG, 31270-901, Brasil. José Pires de Lemos Filho (lemos@icb.ufmg.br), Dept. Botanica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, CP: 486, Belo Horizonte, MG, 31270-901, Brasil.     

Tortula and some related genera (Pottiaceae, Musci): phylogenetic relationships based on chloroplast rps4 sequences

 According to chloroplast rps4 sequence data the genus Syntrichia forms a monophyletic clade clearly separated from Tortula, while Pottia is shown to be polyphyletic and the Rhynchostegiae species (with rostrate lid) are very similar to Tortula. Crossidium is probably polyphyletic. The close affinity of Desmatodon, Stegonia, Pterygoneurum and some of the species of Phascum with Tortula is confirmed by the molecular data. Received May 23, 2002; accepted August 23, 2002 Published online: November 22, 2002 Address of the authors: O. Werner, R. M. Ros, M. J. Cano, J. Guerra (E-mail: werner@um.es) Departamento de Biología Vegetal (Botánica), Facultad de Biología, Universidad de Murcia, Campus de Espinardo, E-30100-Murcia, Spain.     

Tribes of Boraginoideae (Boraginaceae) and placement of Antiphytum, Echiochilon, Ogastemma and Sericostoma: A phylogenetic analysis based on atpB plastid DNA sequence data

 The genera Antiphytum, Echiochilon, Ogastemma and Sericostoma, which have been difficult to place within the tribes of the subfamily Boraginoideae (Boraginaceae), are analysed using plastid atpB sequence data. A selection of Boraginaceae genera was used to obtain a framework for the phylogenetic position of Antiphytum, Echiochilon, Ogastemma and Sericostoma. Sericostoma is found to belong within Echiochilon. The new tribe Echiochileae, Boragineae and Lithospermeae are monophyletic but the tribes Eritrichieae and Cynoglosseae are paraphyletic. The biogeography of Echiochileae (Echiochilon and Ogastemma from Africa and western Asia, and Antiphytum from America) is discussed. Received November 27, 2001; accepted March 20, 2002 Published online: November 14, 2002 ? Springer-Verlag 2002 Addresses of the authors: Elisabeth L?ngstr?m (e-mail: elisabeth.langstrom@ebc.uu.se), Department of Systematic Botany, Evolutionary Biology Centre, Uppsala University, Norbyv?gen 18D, SE-752 36 Uppsala, Sweden. Mark W. Chase, Jodrell Laboratory, Royal Botanic Gardens, Kew, TW9 3DS, UK.     

Numerical taxonomic study of some tribes of Brassicaceae from Egypt

 A systematic study of 45 taxa belonging to 23 genera of tribes Arabideae, Euclidieae, Hesperideae, Lunarieae, Matthioleae and Sisymbrieae of Brassicaceae from Egypt was conducted by means of numerical analysis based on sixty two morphological characters, including vegetative parts, pollen grains and seeds. On the basis of UPGMA clustering and PCO analysis, four main groups are recognised: Lunarieae, Euclidieae, Matthioleae and a mixed group. Representatives of these groups are clustered together based on characters with high factor loading in the PCO analysis. The tribe Euclidieae is the most homogeneous group, and the tribe Arabideae is the most heterogeneous one. Received November 9, 2001; accepted February 21, 2002 Published online: October 14, 2002 Addresses of the authors: K. Abdel Khalik, (e-mail: kadry.elsayedabdelkhalik@wur.nl), L. J. G. van der Maesen (e-mail: jos.vandermaesen@ wur.nl), W. J. M. Koopman, R. G. van der Berg, Group of Biosystematics, Gen. Foulkesweg 37, NL-6703 BL Wageningen, The Netherlands.     

Cleistogamy in the rare high Andean perennial herb Cryptantha capituliflora (Boraginaceae)

 Axial and apical flowers of Cryptantha capituliflora were analyzed with regard to morphology and pollen tube growth to assess the occurrence of cleistogamy. Although intermediate floral forms do occur, cleistogamous flowers were significantly smaller than chasmogamous flowers, had fewer anthers, and showed a distinctive stigmatic surface. Chasmogamous flowers can be cross-pollinated. Nevertheless, the growth of self-pollen tubes in few chasmogamous buds jointly with flower characters suggests that these flowers can probably produce fruits through autonomous selfing. The mean seed number per fruit did not differ between fruits from chasmogamous and cleistogamous flowers. Cleistogamous flowers were only observed in axial inflorescences, which are completely covered by the leaf. Other species of section Cryptantha also show the same trend, with cleistogamous flowers located in the lower half of the stems. This pattern is discussed in relation to dissimilarities in the outcrossing opportunities between flower types within the plant. Received May 22, 2002; accepted November 14, 2002 Published online: March 20, 2003     

Embryology of <Emphasis Type="Italic">Petrosavia</Emphasis> (Petrosaviaceae,Petrosaviales): evidence for the distinctness of the family from other monocots

The affinities of Petrosavia, a rare, leafless, mycoheterotrophic genus composed of two species indigenous to East to Southeast Asia, have long been uncertain. However, recent molecular analyses show that the genus is sister to Japonolirion osense. Japonolirion and Petrosavia comprise the Petrosaviaceae, which are now placed in its own order, Petrosaviales, distinct from other monocots based on molecular analyses. We conducted an embryological study of Petrosavia, comparing it to Japonolirion, as well as to basal monocots (Acorus and Araceae) and more derived monocots (Nartheciaceae, Velloziaceae, and Triuridaceae). Our results showed that Petrosavia is very similar in embryology to Japonolirion, with both genera sharing a glandular anther tapetum, simultaneous cytokinesis in microspore mother cells, anatropous and crassinucellate ovules, T-shaped tetrads of megaspores, ab initio Cellular-type endosperm, and a mature seed coat composed of the exotesta, endotesta, and endotegmen. The two genera of Petrosaviaceae are clearly distinct from Acorus, and all Araceae, Nartheciaceae, Velloziaceae, and Triuridaceae genera in various combinations of characters. Thus, both molecular and embryological evidence support the distinctness of the Petrosaviaceae from other monocots and its placement in its own order, Petrosaviales.     

Evolutionary relationships of the New Caledonian heterotrophic conifer, Parasitaxus usta (Podocarpaceae), inferred from chloroplast trnL-F intron/spacer and nuclear rDNA ITS2 sequences

 The phylogenetic position of Parasitaxus (Podocarpaceae) has been inferred from a cladistic analysis of molecular characters from chloroplast and nuclear genomes including all genera of Podocarpaceae. In all 24 most parsimonious trees, based on combined datasets, Phyllocladus resided outside Podocarpaceae s. str. while Lepidothamnus was basal to the latter. Most other genera were arranged in two major clades. The evidence confirms previous studies, which have suggested a relationship between Lagarostrobos, Manoao and Parasitaxus. Parasitaxus is not directly related to its host Falcatifolium taxoides. Instead it appears to be most closely related to Manoao and Lagarostrobos. No other members of this group now occur on New Caledonia. However, if the evolution of Parasitaxus were autochthonous, a free-living member of this group must once have occurred there. An accelerated evolutionary rate of the chloroplast sequence analysed was suggested, indicating that the plant behaves like a holoparasite. Received January 4, 2002; accepted April 3, 2002 Published online: September 13, 2002     

The enigmatic monotypic crab plover Dromas ardeola is closely related to pratincoles and coursers (Aves, Charadriiformes, Glareolidae)

The phylogenetic placement of the monotypic crab plover Dromasardeola (Aves, Charadriiformes) remains controversial. Phylogenetic analysis of anatomical and behavioral traits using phenetic and cladistic methods of tree inference have resulted in conflicting tree topologies, suggesting a close association of Dromas to members of different suborders and lineages within Charadriiformes. Here, we revisited the issue by applying Bayesian and parsimony methods of tree inference to 2,012 anatomical and 5,183 molecular characters to a set of 22 shorebird genera (including Turnix). Our results suggest that Bayesian analysis of anatomical characters does not resolve the phylogenetic relationship of shorebirds with strong statistical support. In contrast, Bayesian and parsimony tree inference from molecular data provided much stronger support for the phylogenetic relationships within shorebirds, and support a sister relationship of Dromas to Glareolidae (pratincoles and coursers), in agreement with previously published DNA-DNA hybridization studies.     

Vascular construction and development in the stems of certain Pandanaceae

By means of serial sections and cinematographic methods the vascular system in the stems of certain Pandanaceae is analyzed, in both mature axes and developing crowns. This serves to establish the three-dimensional basis for the bi- or tri-polar vascular bundles which are apparent in single sections of stems of all species of Pandanaceae which so far have been examined. The basic "R/iap/s-principle", which characterizes woody monocotyledons, is here expressed in a distinctive way which can be seen as an important developmental variation.     

Partially hydrated pollen: taxonomic distribution, ecological and evolutionary significance

 The problem of the water content of pollen is reconsidered, especially the distinction between “partially hydrated pollen” (PH pollen), pollen with a water content greater than 30%, and “partially dehydrated pollen” (PD pollen), which has a water content of less than 30%. Both types have been found even in systematically contiguous groups or the same genus. Partially hydrated pollen, encountered in at least 40 families of angiosperms, has the advantage of germinating quickly, normally in a few minutes to less than an hour. Dispersal of highly hydrated pollen also occurs in orchids but for a different reason, i.e. to enable packaging of massulae. The disadvantage of pollen dispersed with a high water content is that water is readily lost and the pollen may desiccate and die unless it has biochemical or anatomical devices to retain water or phenological strategies, such as flowering when temperatures are not too high and when relative humidity is high. Most pollen of Gymnosperms and Angiosperms studied has, however, been found partially dehydrated. Received March 8, 2002; accepted April 8, 2002 Published online: November 14, 2002 Addresses of the authors: G.G. Franchi (e-mail: franchi@unisi.it), Department of Pharmacology, Università di Siena, Via delle Scotte 6, I-53100 Siena, Italy; M. Nepi (e-mail: nepim@unisi.it) and E. Pacini (e-mail: pacini@unisi.it), Department of Environmental Sciences, Università di Siena, Via P.A. Mattioli 4, I-53100 Siena, Italy; A. Dafni (e-mail: adafni@research.haifa.ac.il), Laboratory of Pollination Ecology, Institute of Evolution, University of Haifa, 31905 Israel.     

Insect pollination of Musella (Musaceae), a monotypic genus endemic to Yunnan, China

 The pollination biology of Musella lasiocarpa (Franch.) C. Y. Wu ex H. W. Li, a monotypic genus in the banana family (Musaceae) endemic to southwestern China, was investigated. Floral phenology, nectar production, and flower visitors were observed, measured, and recorded. Bagging experiments and comparative breeding system studies were carried out at different study sites and in different seasons. Our results revealed four important aspects of the reproductive biology of Musella. 1) This species blooms year round, but most flowering is concentrated from February to August. The longevity of female flowers is greater than that of male flowers and opening of both types of flowers occurs at anytime during the day, but is concentrated in the morning. 2) Although nectar is produced uniformly while flowers are open, the nectar volume and rate of female flowers are significantly higher than that of male flowers. 3) Insects, such as bumblebees (Bombus eximius and B. montivolans), honeybees (Apis cerana and A. florea), and wasps (Vespa mandarinia) are the primary floral visitors and show a preference for female flowers. 4) Both fruit and seed set are pollinator-limited at both study sites. A comparison of the floral biology and pollination characteristics among the three genera in the banana family suggests that insect pollination has played an important role in the reproductive isolation and breeding system evolution of Musella. Received February 14, 2002; accepted March 26, 2002 Published online: November 22, 2002 Addresses of authors: Aizhong Liu, W. John Kress (correspondence, e-mail: kress.john@nmnh.si.edu), Botany, MRC-166, United States National Herbarium, National Museum of Natural History, Smithsonian Institution, PO Box 37012, Washington DC 20013-7012, USA. Hong Wang, De-Zhu Li (dzl@public.km.yn.cn), Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.     

Molecular evidence for the polyphyly of Olearia (Astereae: Asteraceae)

 Analyses of ITS sequences for 49 species of Olearia, including representatives from all currently recognised intergeneric sections, and 43 species from 23 other genera of Astereae, rooted on eight sequences from Anthemideae, provide no support for the monophyly of this large and morphologically diverse Australasian genus. Eighteen separate lineages of Olearia are recognised, including seven robust groups. Three of these groups and another eight species are placed within a primary clade incorporating representatives of Achnophora, Aster, Brachyscome, Calotis, Camptacra, Erigeron, Felicia, Grangea, Kippistia, Lagenifera, Minuria, Oritrophium, Peripleura, Podocoma, Remya, Solidago, Tetramolopium and Vittadinia. The remaining four groups and three individual species lie within a sister clade that also includes Celmisia, Chiliotrichum, Damnamenia, Pleurophyllum and Pachystegia. Relationships within each primary clade are poorly resolved. There is some congruence between this molecular estimate of the phylogeny and the distribution of types of abaxial leaf-hair, which is the basis of the present sectional classification of Olearia, but all states appear to have arisen more than once within the tribe. It is concluded that those species placed within the second primary clade should be removed from the genus, but the extent to which species placed within the first primary clade constitute a monophyletic group can only be resolved with further sequence data. Received November 12, 2001; accepted April 29, 2002 Published online: November 22, 2002 Addresses of authors: Edward W. Cross, Centre for Plant Biodiversity Research, CSIRO, GPO Box 1600, Canberra, ACT 2601, Australia (E-mail: ed.cross@csiro.au); Christopher J . Quinn, Royal Botanic Gardens, Mrs Macquaries Rd., Sydney, NSW 2000, Australia; Steven J. Wagstaff, Landcare Research, PO Box 69, Lincoln 8152, New Zealand.     

Morphological analysis, phylogenies and classification in Velloziaceae

A morphological (non-molecular) cladistic analysis of the Velloziaceae is presented. The terminal taxa are 47 species of Velloziaceae plus four taxa as outgroups: Acanthochlamys bracteata (Acanthochlamydaceae), Encholirium scrutor (Bromeliaceae), Thoracocarpus bissectus (Cyclanthaceae) and Pandanus racemosus (Pandanaceae). The species of Velloziaceae sampled represent a significant proportion of the morphological diversity of the family, including all recognized genera and sections. The analysis revealed two major groups within Velloziaceae, supported mainly by stomata, vascular bundles in the pedicel, aquiferous tissues, filaments, anthers, pollen, stigma, seeds, ploidy and chemical characters. Comparison between this and the previous phylogenetic hypotheses for Velloziaceae, together with the two conflicting current classifications, suggests that there is incompatibility concerning the support of current genera and sections. The only three groups supported in all phylogenies are Barbacenioideae sensu Menezes (= Barbacenia sensu Smith & Ayensu), Xerophyta sect. Barbacenioides and Xerophyta sect. Xerophyta sensu Smith & Ayensu.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 157–173.     

Genome organization and polyploid evolution in the genus Eleusine (Poaceae)

 Eleusine (Poaceae) includes six diploid and three polyploid species and has three basic chromosome numbers, x=8, 9 and 10. The species are annual as well as perennial and all are wild except E. coracana, which is cultivated for grain and fodder in Africa and the Indian subcontinent. Eleusine coracana and E. africana have the same genome and chromosome number (2n=36). Eleusine indica and E. floccifolia are identified as two genome donors to these polyploid species. Eleusine kigeziensis is the third polyploid species of the genus with 2n=38. Its genome may have come from E. jaegeri and from one of the species with x=9, most probably from E. indica. Eleusine indica, E. tristachya, E. floccifolia and E. intermedia with x=9 and two polyploid species, E. coracana and E. africana, are closely related and there is free genetic flow between them. Eleusine multiflora with x=8 is significantly different in morphology and at genomic level from other species. Eleusine jaegeri with x=10 is morphologically similar to E. indica, however, more information is needed to ascertain its position in the genus. Eleusine coracana, which is commonly called finger millet, is a potential and nutritious crop for the increasing population of the world, particularly in arid and semi-arid regions. It can also serve as a gene pool for various important characters and disease resistant genes. Received February 11, 2002; accepted May 27, 2002 Published online: October 14, 2002 Addresses of the authors: Madho Singh Bisht and Yasuhiko Mukai (e-mail: ymukai@cc.osaka-kyoiku.ac.jp), Laboratory of Plant Molecular Genetics, Division of Natural Science, Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582, Japan.     

Oxypetalum banksii subsp. banksii: a taxon of Asclepiadaceae with an extragynoecial compitum

 The floral morphology of seven Oxypetalum species and, in particular, the spatial relationship between the five stigmatic chambers and two separate ovaries of their flowers with respect to transmission of the pollen tube are studied. In all species, except O. banksii subsp. banksii, floral morphology is similar to that in other Asclepiadeae, and the flowers pollinated with one pollinium develop only one follicle, which means compitum absence. In O. banksii subsp. banksii flowers, the secretory interstaminal tissue lines the inner walls of the stigmatic chambers as in the other species studied, but it also reaches the upper part of the inner surface of the filament tube, where it surrounds the styles, an unprecedented feature for Asclepiadaceae. This tissue secretes nectar and mucilage; the latter acts as transmitting medium for the growth of pollen tubes from pollinia inserted and hydrated in stigmatic chambers (“hyperstigmas”). Mucilage also functions as an extragynoecial compitum: in flowers pollinated with one pollinium both carpels develop into a follicle. Received August 28, 2001; accepted April 9, 2002 Published online: October 14, 2002 Addresses of the authors: Milene Faria Vieira (e-mail: mfvieira@mail.ufv.br), Departamento de Biologia Vegetal, Universidade Federal de Vi?osa, 36571-000, Vi?osa, Minas Gerais, Brazil. George John Shepherd, Departamento de Botanica, Instituto de Biologia, Universidade Estadual de Campinas, C.P. 6109, 13083-970, Campinas, S?o Paulo, Brazil.