Louis P. Ronse De Craene

• Doctor in Science
• Postgraduate Program Coordinator at Royal Botanic Garden Edinburgh

The floral development of Dodonaea viscosa (Sapindaceae) has been investigated under scanning electron microscope and light microscope to understand its floral characteristics and morphological differences from other Sapindaceae caused by a shift to wind pollination. Inflorescences of Dodonaea viscosa are terminal or axillary thyrsoids, occasionall...

Floral adaptation to pollinators often involves key modifications of floral development. We investigated floral development and its function for pollination in Bauhinia galpinii, a legume species native to eastern and southern Africa with a unique arrangement of stamens and staminodes. Flowers and floral buds at different stages were prepared for o...

Floral diversity of Croton, the second largest genus in Euphorbiaceae, is currently under-explored. Several clades demonstrate an unusual floral morphology, e.g., lower or higher stamen number, bilateral symmetry and reduced ovary, but have never been investigated in a comparative study with typical Croton. This study examined morphology and ontoge...

Heterochrony acts as a fundamental process affecting the early development of organisms in creating a subtle shift in the timing of initiation or the duration of a developmental process. In flowers this process is linked with mechanical forces that cause changes in the interaction of neighbouring floral organs by altering the timing and rate of ini...

Stipules are generally regarded as the outgrowths of the leaf base in angiosperms. Other interpretations see stipules as independent organs comparable to leaves. Stipules have been recognized as an important trait for plant taxonomy and identification, and there has been great progress in the understanding of their morphology, development, origin,...

The Primuloid clade or Primulaceae sensus lato is well supported and contains several pollination syndromes, including wind pollination and insect pollination with pollen, nectar, or oil as a reward. Previous studies have recognized two types of nectaries (floral and extrafloral) with different distributions (e.g. ovary, stigma, style, pedicel). Th...

Cyperaceae is a widespread family composed of two subfamilies, Mapanioideae and Cyperoideae. As opposed to the dimerous Mapanioideae spicoid inflorescences, Cyperoideae flowers are known for their typical trimerous Bauplan, however, morphological variation is reported in each floral whorl. This wide range of variation is challenging, mainly regardi...

Epimedium and Plagiorhegma are the representatives of two early-diverging clades in Podophylloideae of Berberidaceae. Flowers are dimerous and trimerous respectively, but their floral development is little known. Here, we used scanning electron microscopy to clarify the structure and development of flower and inflorescence in Epimedium pubescens an...

Although the vast majority of Prunus L. (Rosaceae) species have clearly differentiated sepals and petals, two former genera Maddenia and Pygeum have been described as having an undifferentiated perianth. However, floral morphological and morphogenetic data are scarce, and a renewed investigation is essential to understand the evolution of the peria...

Floral morphology is key for understanding floral evolution and plant identification. Floral diagrams are two-dimensional representations of flowers that replace extensive descriptions or elaborate drawings to convey information in a clear and unbiased way. Following the same outline as the first edition, this comprehensive guide includes updated a...

Floral morphology is key for understanding floral evolution and plant identification. Floral diagrams are two-dimensional representations of flowers that replace extensive descriptions or elaborate drawings to convey information in a clear and unbiased way. Following the same outline as the first edition, this comprehensive guide includes updated a...

The inflorescence, floral structure and ontogeny, and breeding system of the relict woody species Dipteronia sinensis was investigated to understand the developmental basis for its floral Bauplan, more particularly the octandrous androecium, dimerous gynoecium and the occurring flower symmetry in comparison with Sapindaceae. The functionally unisex...

Mechanical forces acting within the plant body that can mold flower shape throughout development received little attention. The palette of action of these forces ranges from mechanical pressures on organ primordia at the microscopic level up to the twisting of a peduncle that promotes resupination of a flower at the macroscopic level. Here, we argu...

Sapindales is a monophyletic order within the malvid clade of rosids. It represents an interesting group to address questions on floral structure and evolution due to a wide variation in reproductive traits. This review covers a detailed overview of gynoecium features, as well as a new structural study based on Trichilia pallens (Meliaceae), to pro...

This review based on a morphological and developmental perspective reveals a striking diversity in shapes and evolutionary trends in the gynoecium of core Caryophyllales that have affected the number of carpels, the formation of septa and the number of ovules. Two major developmental shifts are responsible for the diversity in gynoecial forms and a...

Croton is a mega-diverse genus of more than 1,200 species with great morphological diversity and highly dimorphic flowers. Staminate flowers generally possess petals and a variable number of stamens and lack of an ovary. Pistillate flowers generally lack petals or have filamentous structures instead; stamens are lacking, and the ovary is generally...

The flower of Malesherbia Ruiz & Pav. (Passifloraceae) is a suitable model to study how far growth constraints throughout ontogeny are causal for the variation in the proportions of reproductive structures. The Malesherbia flower is characterized by a marked hypanthium subtending five alternating sepal and petal lobes plus a coronal rim. In Maleshe...

We observed the floral development of Hemiorchis burmanica and two species of Gagnepainia, which make up the sister group of Globba in Globbeae, as well as a selected number of species of Globba. Our observations revealed that in Gagnepainia, a “fifth staminode,” develops as part of the labellum, while it is generally lost in other Zingiberaceae. T...

Most Rosaceae flowers are pentamerous and have petals, but subtribe Sanguisorbinae have small tetramerous (or trimerous) flowers without petals, and their floral morphology and morphogenesis remain poorly known. We investigated the floral development of three Sanguisorba spp. using scanning electron microscopy to clarify the relationship between fl...

Between 2001 and 2017, the Royal Botanic Garden Edinburgh conducted training and research in Belize built around an annual two-week field course, part of the Edinburgh M.Sc. programme in Biodiversity and Taxonomy of Plants , focused on tropical plant identification, botanical-collecting and tropical fieldwork skills. This long-term collaboration in...

Most Rosaceae flowers are pentamerous and have petals, but subtribe Sanguisorbinae have small tetramerous (or trimerous) flowers without petals, and their floral morphology and morphogenesis remain poorly known. We investigated the floral development of three Sanguisorba spp. using scanning electron microscopy to clarify the relationship between fl...

Background and aims: Floral development is a powerful tool to infer homologies of floral organs and to understand floral evolution. Caryophyllaceae is a major family of core Caryophyllales that possesses petal-like structures (petaloids) with a great diversity in shape. The main purpose of this study is to determine the nature of the second whorl...

We investigated the floral anatomy and development of Macarthuria australis Hügel ex Endl., an unusual genus endemic to Australia, in the context of floral evolution of core Caryophyllales. Flower initiation is spiral, with sepals developing quincuncially. The first two petals continue the sequence of sepal initiation, but the remaining petals aris...

Globba is one of the largest genera in the primarily tropical Zingiberaceae. The number of anther appendages is highly diagnostic and has been used along with molecular characters to define subgenera and sections. Four main types of anther morphology are recognized: without appendages and with two, four and six appendages. The six-appendaged anther...

Entre el 5 y 12 de octubre del 2018 se llevó a cabo la primera versión del Curso Intensivo de Morfología Floral de la red FLO-RE-S (Bull-Hereñu et al., 2016) en las dependencias de la Reserva Nacional Río Clarillo (CONAF). La ONG Laboratorio Flores (www.laboratorioflores.cl) tuvo a cargo la planificación y ejecución de este evento cuyos preparativo...

The first FLO-RE-S floral morphology course in Chile.

The floral organogenesis and anatomy of Koelreuteria bipinnata and its variety K. bipinnata var. integrifolia (Sapindaceae) has been investigated to clarify the identity of the two taxa in relation to other species of Koelreuteria, and to understand the shift to monosymmetry in the genus. Although the floral development is highly similar, we found...

A recent study using an extensive data set plus sophisticated analytical tools reconstructed a model of the ancestral angiosperm flower. Although attractive, it presents problems of homology assessment. We discuss its inconsistencies and endorse the use of a comparative model that integrates biological parameters as essential to elucidate floral ev...

The caption of Figure 5 was published incorrectly in the original publication of the article.

Flower morphology results from the interaction of an established genetic program, the influence of external forces induced by pollination systems, and physical forces acting before, during and after initiation. Floral ontogeny, as the process of development from a meristem to a fully developed flower, can be approached either from a historical pers...

We present a comparative flower ontogenetic study in five species of the genus Eucryphia with the aim of testing whether differences in the organ number observed can be explained by changes in the meristematic size of floral meristem and floral organs. Species native to Oceania, viz. E. milliganii, E. lucida and E. moorei, have the smallest gynoeci...

Background and aims: Camptotheca is endemic to China and there are limited data about the breeding system and morphogenesis of the flowers. Camptotheca is thought to be related to Nyssa and Davidia in Nyssaceae, which has sometimes been included in Cornaceae. However, molecular phylogenetic studies confirmed the inclusion of Camptotheca in Nyssace...

Monocots are remarkably homogeneous in sharing a common trimerous pentacyclic floral Bauplan. A major factor affecting monocot evolution is the unique origin of the clade from basal angiosperms. The origin of the floral Bauplan of monocots remains controversial, as no immediate sister groups with similar structure can be identified among basal angi...

Background and aims: Ophiocaryon is a lesser known genus in Sabiaceae. This study examines flowers of six Ophiocaryon species in comparison with Meliosmaalba, to identify taxonomically informative characters for understanding relationships within the family Sabiaceae, to imply previously unknown pollination mechanisms of Ophiocaryon, and to contri...

Premise of research. The floral development of the monotypic genus Medusagyne is investigated to understand the mechanisms of stamen and carpel increases in light of its proposed affinity with Ochnaceae. Methodology. Flowers at different stages of development were investigated with SEM. Pivotal results. Flowering shrubs are andromonoecious. Flowers...

Eurycorymbus is an unusual monotypic genus of Sapindaceae endemic to China. The floral organogenesis of E. cavaleriei has been investigated with the light and scanning electron microscope to clarify its floral characters and its uncertain systematic position. Eurycorymbus cavaleriei possesses several unique characteristics in Sapindaceae. Flowers a...

Background and aims: Berberidopsis beckleri is one of three species of the family Berberidopsidaceae. The flower of Berberidopsis is unusual for core eudicots in being spiral with an undifferentiated perianth. In a previous study of the sister species B. corallina, it was suggested that Berberidopsidaceae represent a prototype for the origin of th...

Small trees, lianas, or shrubs, dioecious; stems erect with libriform fibres; indumentum of eglandular unicellular trichomes, present only in leaf axils. Leaves simple, entire, opposite or alternate, exstipulate, margins entire. Staminate inflorescences axillary, rarely terminal, paniculate; each flower subtended by a bract or with several bracts o...

The first molecular phylogenies of the flowering plant family Ranunculaceae were published more than twenty years ago, and have led to major changes in the infrafamilial classification. However, the current phylogeny is not yet well supported, and relationships among subfamilies and tribes of Ranunculaceae remain an open question. Eight molecular m...

Background and aims: Obdiplostemony has long been a controversial condition as it diverges from diplostemony found among most core eudicot orders by the more external insertion of the alternisepalous stamens. In this paper we review the definition and occurrence of obdiplostemony, and analyse how the condition has impacted on floral diversificatio...

Sapotaceae belongs to the heterogeneous order Ericales and exhibits extensive diversity in floral morphology. Although pentamery is widespread and probably the ancestral condition, some clades are extremely variable in merism, with fluctuations between tetramery to hexamery and octomery, affecting different floral organs to different degrees. We as...

Premise of the study: The phylogenetic position of Ceratophyllum is still controversial in recent molecular analyses of angiosperms, with various suggestions of a sister group relation to all other angiosperms, eudicots, monocots, eudicots + monocots, and magnoliids. Therefore, the morphological characters of Ceratophyllum are important for resolv...

• Flowers of Sabiaceae diverge from basal eudicots in combining pentamery with superposed whorls of sepals, petals, and stamens and are therefore crucial in understanding origins of core eudicot flowers. Different hypotheses are tested using floral developmental evidence, whether the pentamerous flower is derived from a spiral, trimerous, or dimero...

Flowers, the reproductive organs in Angiosperms, are the structures most susceptible to evolutionary pressures in flowering plants. The perianth of eudicot flowers is usually formed by two whorls: a protective whorl formed by sepals (the calyx) and a pollinator-attractive whorl formed by petals (the corolla). In Caryophyllales the perianth is forme...

Flowers of four species of Sabia are investigated using scanning electron and light microscopy to understand the complex floral system of Sabiaceae and to contribute to the understanding of the systematic position of the family among early diverging eudicots. The structure of the mature flower and the floral anatomy are here described and compared...

This paper is a discussion and elaboration of a paper by Prenner & al. (2010), entitled “Floral formulae updated for routine inclusion in formal taxonomic descriptions”. The aim of the Prenner paper was to promote the use of floral formulae in botany and to reach a consensus among botanists for best practice. An important purpose of floral formulae...

The Caryophyllales have the highest diversity in androecial patterns among flowering plants with stamen numbers ranging from 1 up to 4,000. Thanks to the recent progress in reconstructing the phylogeny of core Caryophyllales, questions of floral evolution, such as the origin and diversification of the androecium, can be readdressed. Caryophyllales...

Unlabelled: • Premise of the study: Caryophyllales are highly diverse in the structure of the perianth and androecium and show a mode of floral development unique in eudicots, reflecting the continuous interplay of gynoecium and perianth and their influence on position, number, and identity of the androecial whorls. The floral development of fiv...

Background and aims – The term ‘petal’ is loosely applied to a variety of showy non-homologous structures, generally situated in the second whorl of a differentiated perianth. Petaloid organs are extremely diverse throughout angiosperms with repeated derivations of petals, either by differentiation of a perianth, or derived from staminodes. The fie...

Premise of the study: Zygomorphy has evolved multiple times in angiosperms. Near-actinomorphy is the ancestral state in the early diverging eudicot family Papaveraceae. Zygomorphy evolved once in the subfamily Fumarioideae from a disymmetric state. Unusual within angiosperms, zygomorphy takes place along the transverse plane of the flower. Method...

The flower development of a number of taxa with either unclear or only recently clarified phylogenetic positions in the order Ericales has remained uninvestigated for a long time because of the unavailability of material. Two genera, traditionally placed in the Primulaceae but often described as aberrant, are Ardisiandra, with three African species...

The almost cosmopolitan distribution of Samolus valerandi is unique in the genus Samolus L. (Samolaceae), which also includes 12–15 taxa with distributions restricted to smaller areas of the Southern Hemisphere. Recent molecular phylogenetic studies based on chloroplast and nuclear DNA sequences showed that the widespread S. valerandi and the North...

Stephania is the sole genus in the basal eudicot family Menispermaceae that possesses both actinomorphic and zygomorphic flowers. Variation in perianth merism can have an important impact on flower symmetry and thus eminent biological significance in evolution of Menispermaceae. Using SEM, we studied the floral development of four representative sp...

Eudicots represent the largest clade of flowering plants, comprising approximately 75% of all species and characterised by pollen having three apertures. Eudicots consist of a basal grade and a large (core eudicot) clade, which comprises the majority of species. Evolution of flowers in core eudicots is highly diverse and is driven by repeated diver...

Caryophyllales is an order distinguished for having flowers with only one perianth whorl – the perigone. The perigone is a calyx derived structure that can have either petaloid or sepaloid appearance. Members of the Portulacinae suborder have tendency to have a false bipartite perianth, forming a petaloid perigone and an epicalyx with the subtendin...

The morphology and ultrastructure of fresh pollen from nine species, one including two varieties representing seven genera of Annonaceae are described based on observations with scanning and transmission electron microscopy. The pollen grains are elliptic with a single furrow, or disulculate. Some are globose with no visible aperture or any indicat...

Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from...

For the last 20 years, the development and improvement of molecular methods, based mostly on the comparison of DNA sequences, have been increasingly successful in reconstructing the phylogenetic tree of plants at all hierarchical levels. Consequently, they have contributed greatly to the recent improvement of angiosperm systematics. In addition, th...

The genus Conostegia (Miconieae, Melastomataceae) includes shrubs and trees distributed in the Caribbean, Mexico, Central America, N Andes and Brazil (Schnell, 1996). At present, Conostegia contains about 40 species (Schnell, 1996; Mabberley, 1997), although over 100 names have been applied to the genus in the past. However, the elevated number of...

Napoleonaea is a small genus with about eight to ten species mainly restricted to west and central Africa and extending into southern Africa (Liben, 1971; Frame and Durou, 2001). The genus was initially described by Palisot de Beauvois in 1804 and dedicated to Napoleon Buonaparte (Thompson, 1922; Liben, 1971), but became often misspelled as Napoleo...

Genetic and molecular studies have recently come to dominate botanical research at the expense of more traditional morphological approaches. This broad introduction to modern flower systematics demonstrates the great potential that floral morphology has to complement molecular data in phylogenetic and evolutionary investigations. Contributions from...

Introduction For the last 20 years, the development and improvement of molecular methods, based mostly on the comparison of DNA sequences, have been increasingly successful in reconstructing the phylogenetic tree of plants at all hierarchical levels. Consequently, they have contributed greatly to the recent improvement of angiosperm systematics. In...

Bisexual flowers of Carica papaya range from highly regular flowers to morphs with various fusions of stamens to the ovary. Arabidopsis thaliana sup1 mutants have carpels replaced by chimeric carpel-stamen structures. Comparative analysis of stamen to carpel conversions in the two different plant systems was used to understand the stage and origin...

Imperforate tracheary elements (ITEs) in wood of vessel-bearing angiosperms may or may not transport water. Despite the significance of hydraulic transport for defining ITE types, the combination of cell structure with water transport visualization in planta has received little attention. This study provides a quantitative analysis of structural fe...

Floral development and anatomy of Carica papaya L. have been investigated to shed light on (i) the morphology of the flower, (ii) the structural basis for the pollination mechanism, and (iii) the relationships of the Caricaceae. Carica is mostly dioecious with a strong dimorphism between staminate and pistillate flowers. The development of staminat...

A study of the floral development of Dicentra formosa, Corydalis lutea, and Hypecoum procumbens was carried out to better understand the nature of the androecium in Fumariaceae. Sepals emerge successively in a median position and are followed by two alternating pairs of petals. Four stamen primordia are formed in a diagonal position. They are promp...

The floral development of Coris was investigated to clarify its controversial relationship with either Primulaceae (Primulales) or Lythraceae (Myrtales). We demonstrate that Coris is strongly related to the Primulaceae but differs in a few important features, such as the presence of an epicalyx and partial zygomorphy. The saccate calyx and epicalyx...

The floral ontogeny of the monotypic genus Monococcus (Phytolaccaceae) is investigated with the scanning electron microscope. Flowers arise on pendent racemes and are preceded by a bract and two bracteoles arising successively. In both staminate and pistillate flowers four sepals are incepted in diagonal position. In the staminate flowers four alte...

Annonaceae are one of the largest families of Magnoliales. This study investigates the comparative floral development of 15 species to understand the basis for evolutionary changes in the perianth, androecium and carpels and to provide additional characters for phylogenetic investigation. Floral ontogeny of 15 species from 12 genera is examined and...

The floral ontogeny of two species of Knema and one of Horsfieldia was examined and described using scanning electron microscopy. The perianth is trimerous with three tepals arising in succession. Pistillate flowers have a rounded floral apex with a convex top. The single carpel primordium is initiated along the margin of the bud and develops a pli...

Floral morphology remains the cornerstone for plant identification and studies of plant evolution. This guide gives a global overview of the floral diversity of the angiosperms through the use of detailed floral diagrams. These schematic diagrams replace long descriptions or complicated drawings as a tool for understanding floral structure and evol...

Ranunculaceae presents both ancestral and derived floral traits for eudicots, and as such is of potential interest to understand key steps involved in the evolution of zygomorphy in eudicots. Zygomorphy evolved once in Ranunculaceae, in the speciose and derived tribe Delphinieae. This tribe consists of two genera (Aconitum and Delphinium s.l.) comp...

BACKGROUND AND AIMS; This study is an investigation into the floral development and anatomy of two genera of the small family Salvadoraceae, which belongs to the Brassicales in a clade with Batis and Koeberlinia. Salvadoraceae remains little known, despite its wide distribution in arid areas of the globe. Floral morphological data are scarce, and i...

Blüte und Frucht. Morphologie, Entwicklungsgeschichte, Phylogenie, Funktion, Ökologie. 2nd, fully revised edition. LeinsPeter & ErbarClaudia. Stuttgart: E. Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller). 2008. xii + 412 pp., 258 illustrations, 3 tables. ISBN 978 3 510660 46 9. €49 (hardback). - Volume 66 Issue 2 - L. Ronse De Craene

Flowers of Santalales remain largely unexplored with several questions of homology unanswered despite the large size of the order. Morphological and ontogenetic floral studies have the potential to identify new informative characters. We studied floral development in species of Loranthaceae, Santalaceae, Opiliaceae, and "Olacaceae" with scanning el...

Floral morphology of 16 species of Gunnera representing all six subgenera is examined and described using scanning electron microscopy (SEM). The evolution of 19 flower morphological characters is discussed. Eight of these characters are optimized on a current phylogenetic tree. Character evolution tends to be generally continuous over different cl...

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 t...

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 Magnoli...

RONSE DECRAENE, L.-P. & SMETS, E., 1991. The impact of receptacular growth on polyandry in the Myrtales. The androecium of the Myrtales shows a wide variation in structure and development, linked with an original diplostemony. The difference between a centrifugal stamen inception in Lythraceae against a centripetal inception in other families has b...

In order to investigate the taxonomic value of a number of characters in the elucidation of relationships within the collective genus Polygonum L., and segregate genera Atraphaxis L., Calligonum L., Pteropyrum Jaub. & Spach., Oxygonum Burch., Fagopyrum Mill., Harpagocarpus Hutch. & Dandy and Polygonella Michx., 83 species of the tribe Polygoneae em...

Seventeen morphological characters are described and plotted on a phylogeny of the eudicots. The distribution of perianth characters demonstrates that the currently held view that petals originated from stamens in the core eudicots is not consistent with the predominance of bract-derived petals (bracteopetals). Petals in the core eudicots have the...

A study of the floral ontogeny of Popowia was carried out to investigate the phyllotactic arrangement of the floral organs and occurring trends in the androecium of Annonaceae. The flower buds arise on a common stalk in the axil of a bract. Three sepals emerge in quick succession and are rapidly overrun in size by two whorls of petals. The androeci...

The structure and anatomy of mature flowers of four species of Meliosma is investigated using scanning electron and light microscopy. The vasculature of the flower, including the structure of the gynoecium, is described in detail. The mechanism of stamen maturation and pollen release is illustrated and discussed. The existence of an explosive polli...

Flower developmental studies are a complement to molecular phylogenetics and a tool to understand the evolution of the angiosperm flower. Buds and mature flowers of Meliosma veitchiorum, M. cuneifolia, and M. dilleniifolia (Sabiaceae) were investigated using scanning electron microscopy to clarify flower developmental patterns and morphology, to un...