The distribution and systematic relevance of the androecial character oligomery

Localization of the stamens can be approached by a preliminary distinction between two characters, oligomery and polymery, occurring in two different groups of taxa, respectively the oligomerous complex and the polymerous complex. Oligomery is described by four character states standing in a close semophyletic relationship: diplostemony, obdiplostemony, haplostemony and obhaplostemony. Each character state is analysed for its distribution and systematic value. Diplostemony is the synapomorphic character state for the oligomerous line and has arisen once from a polymerous ancestor or in parallel in different lines. Obdiplostemony arises ontogenetically in three different ways. Loss of one whorl leads either to obhaplostemony, or haplostemony; both character states are believed to represent evolutionary steps of no-return. Secondary increases and reductions of the stamens within a whorl are seen as expressions of the intrinsic variability of the character states and should not be homologized with them. Stamen numbers can be increased by the building-up of complex primordia or by secondary receptacular growth. Reductions of stamens affect one or two whorls of stamens and are caused by lack of space, interactions with the gynoecium and zygomorphy. The distribution of the different character states of oligomery is presented on Dahlgrenograms and the androecia of a number of families and their relationships are discussed. The interactions between oligomery and polymery are analysed as guidelines for a global phylogeny of the Magnoliatae.     

The distribution and systematic relevance of the androecial character polymery

RONSE DECRAENE L. P. AND SMETS E. F., 1993. The distribution and systematic relevance of the androecial character polymery . Two characters, viz. oligomery and polymery, have been previously proposed to circumscribe the localization of the androecium. Their distribution is more or less correlated with two groups of taxa: polymery is found in Magnoliidae, Caryophyllidae, Liliatae and part of Hamamelidae; oligomery is found in Dilleniidae, Rosidae, part of Hamamelidae and Asteridae. Polymery can be described by a number of character states, which are presented in a semophyletical scheme. Spiral polyandry, i.e. a multistaminate and spiral androecium, represents the plesiomorphic condition for all Magnoliophytina and is restricted to the polymerous group. Cyclization, induced by an arrangement of the perianth in trimerous whorls and a fractioning of the continuous plastochron, leads to polycycly, i.e. an arrangement of the stamens in numerous cycles; the outer stamens are usually inserted as pairs or in alternation with the inner perianth parts. From this configuration reduction series in different groups result in androecia with a lower number of stamen whorls (such as tetracycly, tricycly, dicycly and (ob)monocycly). The transition from trimery to pentamery induces a derived stamen configuration by the merging of two tepaline whorls and the loss of some stamens. für ther reductions accompanied evolution in trimerous flowers and led to conditions resembling diplostemony as observed in Caryophyllaceae, some Hamamelidaceae and Ranunculaceae. Secondary increases, as well as reductions of stamens within a whorl must be regarded as gradual variations of each character state. Different trends affecting the number and position of the stamens can globally be traced along different lines. Polymery is consistent with other floral characters, such as the nature of perianth, vasculature (axial and cortical systems) and merosity. The androecium of a number of families and their relationships are discussed.     

Flower development in Abrus precatorius (Leguminosae: Papilionoideae: Abreae) and a review of androecial characters in Papilionoideae

The jequirity bean (Abrus precatorius) is well known because of its shiny black and red coloured seeds and because of the poison (abrin) it contains. The genus Abrus is placed in a monogeneric tribe Abreae which is placed in a relatively isolated systematic position at the base of Millettieae. To contribute to a better understanding of this taxon, a detailed ontogenetic and morphologic analysis of its flowers is presented. Floral primordia are subtended by an abaxial bract and preceded by two lateral bracteoles which are formed in short succession. Sepal formation is unidirectional starting abaxially. All petals are formed simultaneously. The carpel is formed concomitantly with the outer (antesepalous) stamen whorl, which arises unidirectionally, starting in an abaxial position. In the inner, antepetalous stamen whorl two abaxial stamens are formed first, followed by two lateral stamen primordia. The adaxial, antepetalous position remains organ free (i.e. this stamen is lost). Later in development the nine stamen filaments fuse to form an adaxially open sheath. The filament bases of the two adaxial outer-whorl stamens grow inwards, possibly to provide stability and to compensate for the lost stamen. In the mature flower a basal outgrowth can be found in the position of the lost stamen. However this is more likely to be an outgrowth of the filament sheath rather than a remnant of the lost stamen. These ontogenetic patterns match in parts those found in other Millettieae (unidirectional formation of sepals and stamens, simultaneous petal formation). In contrast, the complete loss of a stamen is rather unusual and supports the isolated position of Abreae and probably justifies (among other characters) its tribal status. A review of androecial characters shows that androecial merosity is on the one hand extremely variable among Leguminosae, varying from a single stamen per flower to more than 500. On the other hand it is noteworthy that the number of stamens becomes stabilised in more derived Papilionoideae such as the large non-protein-amino-acid-accumulating clade (NPAAA clade). This indicates that the androecium has played an important role in the success of a major part of Leguminosae.     

The distribution and systematic position of the Thermosbaenacea

Summary The oasis of El Hamma, southern Tunisia, was visited in September 1950 and 714 specimens of Thermosbaena mirabilis Monod were collected from two baths fed by hot-springs, Ain el Bordj, the type-source, and Ain Sidi Abd el Kadar where the animal had not previously been recorded. The specimens consisted of 164 males, 123 females (73 non-breeding; 50 with brood-pouches), and 94 juveniles; 333 specimens were unfortunately lost on the return journey. Thermosbaena lives in warm brackish water and can survive temperatures fluctuating between 37° and 47° C. but becomes moribund around 35° and dies around 30° C.Apart from examining the springs and baths at El Hamma, a search was made for Thermosbaena in 14 wells and 11 springs scattered over a wide area around El Hamma and Gabès; the River El Hamma was also sampled. The search proved negative in all but the two El Hamma baths already specified. It is suggested that the animal occupies an interstitial habitat in the thermal ground-water at El Hamma, and that it has been collected in the baths not because it has been brought there by the springs flowing into them (as previously believed), but because in the baths the collector has by chance had access to the interstitial habitat. There are grounds for believing that the three species of Monodella discovered on the Italian and Yugoslavian coasts (M. stygicola, M. argentarii, and M. halophila) are also interstitial forms, and that an ancestral habitat in the sea-bed of that part of the Mesogean (Tethys) Sea now represented by the Mediterranean was common to all members of the Thermosbaenacea. The palaeogeographic history of the Mesogean in the North African, Italian, and Yugoslavian areas is discussed and two hypotheses are formulated to account for the present-day habitat of Thermosbaena. The first would regard the organism as a legacy from the final retreat of the Mesogean from southern Tunisia in the lower Eocene. The second envisages the establishment of ancestral stock in a lake lying nearby El Hamma at a time during the Quaternary when a rise in the level of the Mediterranean had converted the lake into a brackish lagoon. This lake subsequently dried out to form the present-day Chott Djerid and it is suggested that Thermosbaena colonized the thermal brackish ground-water at El Hamma as a measure of survival in face of the increasingly saline ground-water of the developing chott. The second hypothesis is regarded as the most plausible. It is considered that the coastal locations of the Monodella species so far discovered indicate a comparatively recent colonization from the sea-bed of the Mediterranean via littoral ground-water. It is pointed out, however, that the palaeogeographic history of Italy and Yugoslavia renders the occurrence of as yet undiscovered species in the Italian and Balkan interior a distinct possibility, the organisms persisting as freshwater or brackish survivors of the Mesogean regression which followed the Pliocene.The systematic position of the Thermosbaenacea is reviewed in the light of recent work and it is concluded that little significance should be attached to the intermediate position of the order between the Peracarida and Syncarida suggested by Taramelli (1954), or to the stomatopodan affinities of the group suggested by Glaessner (1957). It would appear that these relict malacostracans should either be included in the Peracarida, or placed in a pre-peracaridan position as advocated by Siewing (1956, 1958), but the inclusion of the Thermosbaenacea in a new division Pancarida (Siewing, 1958), equivalent in rank to the Peracarida, is clearly premature.

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Sommaire En septembre 1950, au cours d'une visite à El Hamma, oasis au sud de la Tunisie, 714 spécimens appartenant au genre Thermosbaena mirabilis Monod furent récoltés dans deux bassins alimentés par des sources thermales, Ain el Bordj, source typique, et Ain Sidi Abd el Kadar, où jamais encore de tels échantillons n'avaient été trouvés. Cette collection comprenait: 164 mâles, 123 femelles (73 stériles et 50 avec poches reproductrices) et 94 non-adultes. Malheureusement 333 de ces animaux furent perdus durant le voyage de retour. Thermosbaena vit dans une eau chaude et saumâtre, elle peut survivre à des temperatures variant de 37° à 47° C., mais elle commence à s'éteindre aux environs de 35° et meurt aux approches de 30° C.Une recherche pour trouver Thermosbaena fut entreprise, non seulement dans les deux bassins à El Hamma, mais aussi dans 14 puits et sources disséminés sur une large étendue autour d'El Hamma et de Gabès, ainsi que dans la rivière El Hamma dont des échantillons furent analysés. Rien ne fut trouvé en dehors des deux sources mentionnées en premier lieu. On suppose que ces animaux habitent certains interstices dans les fonds des sources thermales d'El Hamma, et qu'ils y ont été trouvés, non pas parce que amenés la par l'écoulement des eaux, mais parce que le collectionneur eut la chance d'acceder à leur terrain d'habitat. Il est raisonnable de croire que les 3 espèces de Monodella trouvées sur les côtes d'Italie et de Yougoslavie (M. stygicola, M. argentarii, et M. halophila) sont aussi du genre habitant des interstices et qu' un ancien habitat, dans les fonds de cette partie de la Mer mésogéenne (Tethys) maintenant réprénté par la Méditerranée était commun à tous les membres des thermosbenacés. L'histoire paléogéographique du Mésogée dans les régions nord-africaines, italiennes, et yougoslaves est en discussion et on formule deux hypothèses pour expliquer le présent habitat de Thermosbaena. La première considérait l'organisme comme un legs de la retraite finale du Mésogée depuis la Tunisie méridionale dans l'Eocène inférieure. La seconde envisage l'établissement d'une réserve ancestrale dans un lac se trouvant près d'El Hamma à une époque où un relèvement du niveau de la Méditerranée avait converti le lac en un lagon saumâtre. Ensuite ce lac s'est asséché pour former l'actuel Chott Djerid et on formule la suggestion que les Thermosbaena ont colonisé l'eau thermale saumâtre à El Hamma comme mesure de survie devant l'eau de plus en plus salée du chott en voie de dévéloppement. La deuxième hypothèse est estimée comme la plus plausible. On considère que la position sur la côte de l'espèce Monodella, dans la mesure où elle a été découverte, indique une colonisation comparativement récente partant du lit de la Méditerranée par l'intermédiaire des eaux littoraux. On souligne, cependant, que l'histoire paléogéographique de l'Italie et de la Yougoslave fait de la trouvaille d'espèces non encore découvertes dans l'Italie et l'intérieur des Balkans une possibilité distincte, les organismes persistant comme survivants d'eau douce ou saumâtre de la regression mésogéene qui suivit le Pliocène.La position systématique des thermosbenacés a été mise au point au cours de trauvaux récents, et l'on arrive à conclure que la position intermédiaire de l'ordre entre la Peracarida et la Syncarida, comme suggeré par Taramelli (1954), ou les affinités stomatopodéennes au groupe suggeré par Glaessner (1957) signifient peu de choses. Il semblerait que ces résidus malacostracéens devraient être inclus à la Peracarida ou placés dans une position pré-peracaridéenne, comme le recommande Siewing (1956, 1958), mais établir que les thermosbenacés sont une branche nouvelle Pancarida (Siewing, 1958) à un rang semblable à la Peracarida, serait certainement une conclusion prematurée.

     

Leaf flavonoids as systematic characters in the genera Lavandula and Sabaudia

A comprehensive survey of the leaf flavonoids of the genus Lavandula and the related Sabaudia group was carried out using two-dimensional paper chromatography and high-performance liquid chromatography. The flavonoid patterns obtained were found to be systematically informative at the infrageneric level. Three main groupings were identified: the first containing sections Lavandula, Dentata and Stoechas characterised by the accumulation of flavone 7-glycosides; the second containing sections Pterostoechas, Subnuda and Chaetostachys characterised by the accumulation of 8-hydroxylated flavone 7-and 8-glycosides; the third encompassing the Sabaudia group and accumulating both flavone and 8-hydroxylated flavone 7- glycosides. Such a grouping of taxa is congruent with data from other disciplines, although it is not recognised in any present classifications. The taxonomic and evolutionary implications of the flavonoid data are discussed.     

Systematic relevance of pollen and orbicule characters in the tribe Hillieae (Rubiaceae)

Pollen and orbicule morphology of 26 species in the tribe Hillieae is described based on observations by light, scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the tribe. Pollen is 3-zonocolporate with a perforate, microreticulate, reticulate or eutectate sexine. In the two species of Blepharidium , however, the pollen has one, four or five apertures. These pollen morphological data were incorporated into an existing macromorphological matrix of the group and cladistically analysed. The resulting phylogenies indicate that it may be appropriate to reduce Cosmibuena to a subgenus of the genus Hillia , while Blepharidium should be removed from Hillieae because of the deviating pollen type that is unique to the Rubiaceae. All species investigated produce orbicules, which are mostly spherical and possess an electron-lucent core that is sometimes characteristically flattened.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 303−321.     

Notes on the Evolution of Androecial Organisation in the Magnoliophytina (Angiosperms)

This paper aims to summarize briefly and to update our ideas about androecial architecture formulated in earlier publications. Ontogenetic evidence of stamen development, viz. the initiation, arrangement and relationship of stamens to other floral morphomes, can be translated into a semophyletic scheme reflecting the phylogeny of the androecium. The ancestral androecium is discussed in the light of recent theoriesabout angiosperm phylogeny. Two divergent androecial processes are proposed for the angiosperms starting from a spiral androecium with a moderate number of stamens. However, transitions exist between spiral polyandry, numerous stamens in whorls, and chaotic polyandry. From an androecium with several alternating whorls of paired and single stamens, outer stamen pairs are retained following the successive loss of inner stamen whorls. Single stamens instead of pairs occur at the very end of this line and represent a more advanced condition. This line is mostly present in tri- and dimerous flowers. From the same starting point diplostemony (with two alternating whorls of single stamens) originated, again giving rise to various states usually present in pentamerous or tetramerous flowers.     

The systematic relevance of fruit and seed structure in Bersama and Melianthus (Melianthaceae)

 The fruit and seed anatomy and morphology of the two genera Bersama and Melianthus (Melianthaceae, Sapindales) have been studied in an effort to clarify their systematic position. On the basis of the differences in pericarp and seed anatomy as well as in other exomorphic characters the segregation of Bersama into a distinct family Bersamaceae is supported. Evidence mainly from seed anatomy and morphology emphasizes the anomaly of the traditional inclusion of Bersama and Melianthus in the Sapindales, since they have a distinct seed-coat structure and seed vascularization. The fruit and seed anatomy does not confirm any relationships with alternatively suggested exo-mesotestal Lardizabalaceae. The exotestal seed coats of Bersama and Melianthus with a differentiated palisade of Malpighian cells in the exotesta, dimerous raphal vascular skeleton, abundant endosperm, and a small differentiated straight embryo show a resemblance with the exotestal albuminous seeds of Rhamnaceae and Elaeagnaceae. Using also additional data on fruit, floral and vegetative morphology it is suggested that Bersamaceae with Melianthaceae and Rhamnaceae/Elaeagnaceae constitute a distinct relict side-branch of exo-mesotestal rosidaceous ancestry, the new order Melianthales in the superorder Rhamnanae (Rosidae). The formerly suggested relationship of this side-branch to exotegmic Malvales is not supported by seed anatomy. The affinity with exotegmic Celastrales, which are considered as a possible connecting link between archaic exo-mesotestal Rosales and exotestal Rhamnales/Elaeagnales, is also found untenable. Received May 12, 2000 Accepted December 7, 2000     

Structural characters of leaf epidermis and their systematic significance in Vitaceae

Leaf epidermis of 37species representing 11 genera of Vitaceae was investigated using light microscopy（LM）and scanning electron microscopy（SEM）.The shapes of leaf epidermal cells are usually irregular or polygonal;the patterns of anticlinal walls are stra     

Morphological characters of leaf epidermis in schisandraceae and their systematic significance

The leaf epidermis of 23 species belonging to 2 genera within Schisandraceae was investigated using light and scanning electron microscopy. Many characters of the leaf epidermis in Schisandraceae, such as shape of epidermal cells, type of stomata, and cuticular ornamentation, are usually constant within species and thus helpful for elucidating the relationship between and within genera. Leaf epidermal cells are usually irregular or polygonal in shape. The patterns of anticlinal walls are straight, sinuolate, sinuous or sinuate. The stomatal apparatus belong to paracytic or laterocytic type and the latter is subdivided into various subtypes based on the number and arrangement of subsidiary cells. Under scanning electron microscopy observation, the cuticular membrane is often striated, sometimes squamulate or granular; the inner margin of the outer stomatal rim is nearly smooth or denticulate. Evidences from shape of epidermal cells, patterns of cuticular intrusions between the ends of each guard cell of a pair and distribution of stomatal apparatuses support the viewpoint thatKadsura is more primitive thanSchisandra. Study on leaf epidermis also shows thatKadsura interior deserves the rank of a distinct species and the treatment of the evergreen groups, includingS. propinqua andS. plena, as distinct from the deciduous species of the genus is quite natural.     

葡萄科植物叶表皮特征及其系统学意义

在光学显微镜和扫描电镜下,对葡萄科Vitaceae11属37种代表植物的叶表皮特征进行了观察,发现该科植物叶表皮细胞形状为无规则形或多边形,垂周壁一般为平直、弓形或浅波状;气孔器通常仅分布在下表皮（火筒树属Leea偶尔可在上表皮观察到）,除无规则型（地锦属Parthenocissus、俞藤属Yua、葡萄属Vitis、蛇葡萄属Ampelopsis和酸蔹藤属Ampelocissus）最为常见外,不等细胞型（火筒树属）、短平列型（白粉藤属Cissus、乌蔹莓属Cayratia和崖爬藤属Tetrastigma）、     

The systematic relevance of fruit and seed anatomy and morphology of Akania (Akaniaceae)

The fruit and seed anatomy and morphology of Akania bidwillii , the monotypic genus in the Akaniaceae, have been studied in an effort to clarify its systematic position. The loculicidal (1,2-) 3-locular fruit with Ugnified fibrous 6–7-layered endocarp is clearly of capsular type. Seeds of Akania are relatively large, smelling of bitter almonds, abundantly albuminous, with straight dicotyledonous embryo. The seed coat of Akania is exo-mesotestal with fully obliterated tegmen in early stages; 1-layered exotesta represented by columellar thick-walled cells with numerous invaginations of inner cell walls; mesotesta 25–35-layered, composed of thick-walled, but not lignified mostly rounded sclereids filled with tanninlike substances, the innermost part of mesotesta is aerenchymatous, sometimes collapsed, and traversed by 6(8) postchalazal vascular bundles, 2–3 layers of endotesta composed of enlarged cuboid cells with heavily thickened walls. Evidence mainly from seed morphology and anatomy of seed coats emphasizes the anomaly of the traditional inclusion of Ankaniaceae in the Sapindales, being quite distinct in spermoderm structure and origin from both Sapindaceae and Staphyleaceae in particular as well as from other families of the order, excepting somewhat anomalous exo-mesotestal Bretschneideraceae. Furthermore, seed anatomy does not confirm any relationships with Capparales. It is suggested that Akaniaceae together with Bretschneideraceae constitute a distinct relict side-branch of connaraceous-sapindaceous ancestry tracing back to primitive exo-mesotestal Resales. On the basis of available data of seed coat anatomy it is appropriate to remove archaic Akaniaceae with Bretschneideraceae from more advanced Sapindales. Furthermore, widi the addition of more data on carpology and seed anatomy of basal Rosidae the systematic position of the family should be redefined in terms of its primitiveness and the lack of close relationships with Sapindales.     

三峡水库初次蓄水后干流库区枝角类的空间分布与季节变化

为了阐明三峡水库初次蓄水后干流库区枝角类的时空分布规律, 2004年4月至2005年1月, 在600余公里干流库区设置10个样点, 定性和定量采集枝角类标本。本次调查共采到9种枝角类, 其中春季8种, 夏季5种, 秋季2种, 冬季3种。枝角类种类组成的空间分布差异明显, 河流状态的江段有4种, 水库状态的江段有7种, 水库状态的江段距大坝越近, 枝角类种类越丰富。枝角类的密度和生物量的空间分布和季节变化规律一致, 季节间差异极显著(P<0.01), 春季最高, 夏季次之, 秋季和冬季较低; 空间分布上表现为在干流库区的纵向分布上差异极显著(P<0.01), 河流状态样点远低于水库状态的样点, 水库上游江段又低于下游坝前段。结果显示三峡水库的枝角类具有明显的纵向分布和季节变化特征。     

The coumarins of Philotheca sensu lato: distribution and systematic significance

Five coumarins and two flavonoid glycosides are reported from Philotheca pinoides of which one, 3-(3-hydroxy-3-methylbut-1-enyl)-7,8-dimethoxycoumarin, appears to be novel. HPLC analysis of extracts of a number of other Philotheca species revealed that 5,7-dioxygenated-6,8-prenylated coumarins were present in P. apiculata, P. coccinea, P. deserti, P. pachyphylla, P. rhomboidea, P. thryptomenoides and P. gardneri, but not in P. nodiflora, P. pinoides, P. sericea, P. spicata, P. tomentella or P. woganensis. An analysis of the distribution of coumarins demonstrate that Geleznowia verrucosa is chemically indistinguishable from many species of Philotheca section Philotheca, whereas Philotheca section Erionema is more variable. Typical avicennol type coumarins have been found in the Boronieae only in Philotheca section Philotheca, in Geleznowia and in one species of Asterolasia. Coumarins that characterise Philotheca section Philotheca are not currently known from Eriostemon s.s., and sympatric genera such as Phebalium and Drummondita.     

Phloridzin: Biosynthesis,distribution and physiological relevance in plants

The phenolic compound phloridzin (phloretin 2′-O-glucoside, phlorizin, phlorrhizin, phlorhizin or phlorizoside) is a prominent member of the chemical class of dihydrochalcones, which are phenylpropanoids. The apple tree (Malus sp.) accumulates high amounts of phloridzin, whereas few other species contain this compound only in low amounts. Additionally, Malus sp. show a species- and tissue-specific distribution of phloridzin and its derivatives. Whereas the physiological role of phloridzin in planta is not fully understood, the effect on human health – especially diabetes – and membrane permeability is well documented. The biosynthesis of phloridzin was investigated only recently with recombinant enzymes and plant protein extracts and involved a NADPH-dependent dehydrogenase, chalcone synthase and UDP-glucose:phloretin 2′-O-glycosyltransferase.     

Floral morphology of Maloideae (Rosaceae) and its systematic relevance

Flowers of 169 species of Rosaceae subfamily Maloideae, which were chosen to represent the taxonomic and geographic diversity of the group, were studied to ascertain their morphological variation and its systematic relevance. We describe and illustrate variation in size, indumentum, color, and macroscopic structural features. Most maloid species have syncarpous flowers with two to five carpels in which the ovary is at least three-quarters inferior, whereas species of other Rosaceae subfamilies have apocarpous or unicarpellate flowers with superior ovaries. However, maloid flowers show significant variation in the degree of carpel connation and of ovary adnation to the hypanthium. Cotoneaster, Heteromeles, and Pyracantha are completely apocarpous, and Dichotomanthes is perigynous with a completely superior ovary. Thus, no one floral character is sufficient to separate the Maloideae from other subfamilies of Rosaceae. Differences among their flowers support our recognition of Malus, Pyrus, and Sorbus as separate genera. Further, we argue for removal of Docyniopsis and Eriolobus from Malus, division of Sorbus into several genera, and union of Aronia, Photinia, and Stranvaesia. No floral characters support the traditional dichotomy of the subfamily into tribes Crataegeae and Sorbeae.     

Dédoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

RONSE DECRAENE, L. P. & SMETS, E F., 1993. Dedoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina. There has been much controversy about dedoublement in the past. Dedoublement was originally described as a process of doubling of a (stamen) primordium up to two equivalent primordia. Later, it was extended to explain occurrences of higher stamen numbers, even without evidence of a division. Different interpretations from both opponents and protagonists of dedoublement are critically examined and concepts such as negative, positive, serial, lateral and congenital dedoublement are discussed. Some case studies are presented to evaluate the concept of dedoublement. Paired stamens are not necessarily the result of splitting; they can also arise by a spatial shift, connected with the cyclization of a spiral flower. Two smaller stamen primordia replacing a stamen without visible splitting and a primordium dividing ontogenetically into a stamen pair are essentially similar. The morphological difference between both configurations can be explained by the principle of variable proportions. Radial dedoublement and stamen-petal complexes are examples of meristem fusion (absorption) and may be defined by the term 'negative dedoublement' in the sense of Celakovsky (1894). A distinction between 'dedoublement' sensu stricto and 'polygenesis' is proposed.     

The manifold characters of orbicules: structural diversity,systematic significance,and vectors for allergens

In the anthers of flowering plants, gymnosperms, and seed ferns, tiny (±1?μm) granules might occur on the radial and innermost tangential wall of secretory tapetum cells. These sporopollenin granules develop simultaneously with the pollen exine and are called orbicules or Ubisch bodies. The present paper focuses on two quite different topics associated with orbicules.

The morphological and ultrastructural diversity of orbicules in the order Gentianales is summarized, and it is demonstrated that orbicules are a plesiomorphic feature in the order. Furthermore, orbicule characters seemed to be correlated with evolutionary trends in pollen dispersal unit and tapetum type features.

In the second part, we report on our investigation of Corylus avellana L. (Hazel) pollen, using immunogold electron microscopy to gain an insight into the possible role that orbicules may play as a vector of pollen allergens. During the pollen season orbicules are dispersed into the atmosphere along with Hazel pollen grains. The localisation of homologues of the new birch pollen allergen Bet v 7 was studied at the subcellular level in Hazel anthers. The results of this study indicate that orbicules and pollen of Hazel might act as very effective vectors for homologues of Bet v 7 and that debris of Hazel anthers represent vectors of allergens after the pollen season.