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Papers by Louis P Ronse De Craene

Research paper thumbnail of Floral Development of Three Maesa Species, with Special Emphasis on the Position of the Genus within Primulales

Research paper thumbnail of Floral Development and Anatomy ofMoringa oleifera(Moringaceae): What is the Evidence for a Capparalean or Sapindalean Affinity?

Research paper thumbnail of Floral Development of Cochlospermum tinctorium and Bixa orellana with Special Emphasis on the Androecium

American Journal of Botany, 1989

Research paper thumbnail of The floral development of Pleuropetalum darwinii, an anomalous member of the Amaranthaceae

Research paper thumbnail of D�doublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

Research paper thumbnail of Floral Development of Galopina tomentosa with a Discussion of Sympetaly and Placentation in the Rubiaceae

Systematics and Geography of Plants, 2000

Page 1. Syst. Geogr. Pl. 70: 155-170 (2000) Floral development of Galopina tomentosa with a discu... more Page 1. Syst. Geogr. Pl. 70: 155-170 (2000) Floral development of Galopina tomentosa with a discussion of sympetaly and placentation in the Rubiaceae Louis P. Ronse Decraene* & Erik F. Smets ... 15. Lateral view of older bud with differentiation of the anthers. ...

Research paper thumbnail of On the Wood and Stem Anatomy of Monococcus echinophorus (Phytolaccaceae s.l.)

Systematics and Geography of Plants, 2000

ABSTRACT Wood of the Australian monotypic genus Monococcus is characterised by short, narrow vess... more ABSTRACT Wood of the Australian monotypic genus Monococcus is characterised by short, narrow vessel elements, simple and non-bordered perforation plates, alternate vessel pitting, short fibres with vestigial pit borders, scanty axial parenchyma, and multiseriate rays mainly composed of upright/square ray cells. Styloids are most abundantly present in the secondary phloem. Moreover, secondary growth produced by successive cambia occurs in woody stem parts. These data are compared to other Phytolaccaceae s.l. and a close relationship between Monococcus, Rivina and Petiveria (Rivinoideae or Rivinaceae) is confirmed. However, data on a wider range of taxa are required to support a separation of Rivinaceae from Phytolaccaceae s.s. on the basis of stem anatomy. The presence or absence of successive cambia represents useful taxonomic information for evaluating phylogenetic relationships in Phytolaccaceae s.l. and Caryophyllales.

Research paper thumbnail of Staminodes: Their morphological and evolutionary significance

The Botanical Review, 2001

Research paper thumbnail of Theligonum cynocrambe: Developmental morphology of a peculiar rubiaceous herb

Plant Systematics and Evolution, 1998

Research paper thumbnail of Floral ontogeny and anatomy inKoelreuteria with special emphasis on monosymmetry and septal cavities

Plant Systematics and Evolution, 2000

... sepal 4 (cf. Radlkofer 1897: "schiefe Symmetrie"; Eichler 1878: "schr~ge Zygom... more ... sepal 4 (cf. Radlkofer 1897: "schiefe Symmetrie"; Eichler 1878: "schr~ge Zygomorphie") and differs from the current pattern with the symmetry line more or less crossing the median plane (median zygomorphy). Oblique zygo ...

Research paper thumbnail of Ontogeny and evolution of the flowers of South African Restionaceae with special emphasis on the gynoecium

Plant Systematics and Evolution, 2002

ABSTRACT . The South African Restionaceae make up a highly diverse group of genera displaying sev... more ABSTRACT . The South African Restionaceae make up a highly diverse group of genera displaying several reductive trends in the configuration of the flower, especially in the gynoecium. In this paper the floral ontogeny of fourteen species representing nine of the 11 genera of the Restio clade is studied with the SEM. Although flowers are basically simple, the variability in both mature and developmental stages is striking. Differences between species are the result of changes in growth rate, coupled with differential pressures of organs. Trends in the elaboration of bracts, perianth, androecium and gynoecium are compared. Together with data that have been presented elsewhere about the other clade of African Restionaceae, viz. the Willdenowia-clade, a scheme with potential developmental pathways is proposed and the most evident routes are selected based on ontogenetic evidence. Nine possible reductions are presented arising through three main routes.

Research paper thumbnail of Complex polyandry in the Magnoliatae: definition, distribution and systematic value

Nordic Journal of Botany, 1992

ABSTRACT A revised definition of complex polyandry is presented for the Magnoliatae. The differen... more ABSTRACT A revised definition of complex polyandry is presented for the Magnoliatae. The differences between primary polyandry and secondary (complex) polyandry are clarified. Fascicled stamens are probably not primitive in Magnoliatae. Complex polyandry finds its origin by an increase of stamens in an oligandrous framework. Multiplications of stamens occur either on primary complex primordia, which follow the regular phyllotactic sequence in the flower, either on a girdling primordium (ringwall). The primary primordia may be fully developed before a secondary proliferation of stamens takes place or provide room for more stamens by a continuing growth process. This happens by the development of a staminal tube (e.g. Malvales) or by the growth of a hypanthium (e.g. Myrtales). A typical floral vasculature is developed concomitantly with complex polyandry. Stamen trunk bundles (stamen fascicle traces) are correlated with preformed complex primordia and the absence of a hypanthium. The inception of a ringwall is responsible for a higher complexity in vasculature and for obscuring the identity of the trunk bundles. The presence of a hypanthium does not permit trunk bundle formation because stamens develop on a limited section of the hypanthial slope. In that case the vasculature is characteristically represented by few large bundles linked with the perianth and the androecium. The distribution of complex polyandry is plotted on a Dahlgrenogram and presented in a table. The systematic relevance of complex polyandry is limited to the lower taxonomic (e.g. familial) levels.

Research paper thumbnail of A floral ontogenetic investigation of the Hydrangeaceae

Nordic Journal of Botany, 1997

As a first step towards a broader floral ontogenetic study on Cornales, the flowers of four speci... more As a first step towards a broader floral ontogenetic study on Cornales, the flowers of four species of Hydrangeaceae (Deutzia corymbosa, Kirengeshoma palmata, Philadelphus purpurascens and Hydrangea petiolaris) were studied. In Deutzia and Kirengeshoma five sepal primordia are generally initiated, in Philadelphus only four. Sepal initiation in Kirengeshoma shows a tendency to tetramony. Deutzia has a variable sepal initiation. Petal growth was never retarded in the studied species. Initiation of the androecium in Kirengeshoma, Philadelphus and Hydrangea starts with antesepalous primary primordia, on which secondary primordia are soon formed, leading ultimately to the formation of polystaminate androecia. In Deutzia a diplostemonous androecium is formed, starting with the initiation of the antesepalous stamen primordia. Gynoecium development is similar in all species studied: on a concave floral apex, a ring meristem is initiated; it develops into a variable number of continuous carpel primordia, while the centripetally growing common margins form the septa. Initiation of the ovule primordia starts halfway up each placenta and extends in an apical, basal and lateral direction. A number of morphological problems are discussed, such as the derivation of tetramery, and evolutionary and developmental trends in the androecium and gynoecium. Kirengeshoma is well settled in Hydrangeaceae, although its exact position within the family remains uncertain. A sistergroup relationship of Hydrangeaceae with Loasaceae is supported. However, Hydrangeaceae also share features with Saxifragaceae (e.g. similar gynoecium development).

Research paper thumbnail of The floral development of Popowia whitei (Annonaceae)

Nordic Journal of Botany, 1990

ABSTRACT A study of the floral ontogeny of Popowia was carried out to investigate the phyllotacti... more ABSTRACT 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 androecium is initiated centripetally in successive whorls. A first whorl of three pairs of outer staminodes emerges opposite the outer petals and is followed by nine staminodes. Next a whorl of nine fertile stamens arises in alternation with the second whorl of staminodes. The carpels arise in three alternating whorls of nine. The nature of the perianth parts is morphologically identical. The process of cyclisation of the androecium from a spiral is discussed for Annonaceae and Magnoliidae in general. The inception of the three outer stamen pairs is a widespread reductive step for multistaminate androecia in the process of oligomerization. It is proposed to define the cyclic inception of numerous stamens as whorled polyandry, being an intermediate step between true polyandry and a reduced stamen number in whorls. The absence of a cup-like shape in the carpel development is related to the flattened receptacle.

Research paper thumbnail of Pseudodiplostemony, and its implications for the evolution of the androecium in the Caryophyllaceae

Journal of Plant Research, 1998

Research paper thumbnail of Floral Ontogenetic Evidence in Support of the Willdenowia Clade of South African Restionaceae

Journal of Plant Research, 2001

Research paper thumbnail of Similarities in Floral Ontogeny and Anatomy between the Genera Francoa (Francoaceae) and Greyia (Greyiaceae)

International Journal of Plant Sciences, 1999

A comparative study of the floral ontogeny and anatomy of Francoa, with one species, and Greyia, ... more A comparative study of the floral ontogeny and anatomy of Francoa, with one species, and Greyia, with three species, is made. Flowers arise nearly synchronously on terminal raceme‐like inflorescences with abortive growing tip. In Greyia, development of flowers shows a tendency toward monosymmetry, expressed in the initiation sequence of floral organs. Both genera are weakly obdiplostemonous by a later displacement of antepetalous stamens (“secondary obdiplostemony”), and they develop a comparable semi‐inferior, strongly grooved ovary with axile placentation. The staminodial nature of nectaries is rejected for both genera. The floral ontogenetic, anatomical, and morphological similarities of the two genera are obvious and are consistent with the proposal for a close relationship between Greyia and Francoa supported by molecular data.

Research paper thumbnail of The floral development and floral anatomy of Coris monspeliensis

Canadian Journal of Botany, 1995

The floral development of Coris was investigated to clarify its controversial relationship with e... more 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 with unilateral development encloses an actinomorphic flower. The stamen–petal tube has two sections that arise through three growth processes: a lower common part for stamens and petals and an upper section representing a fused corolla. The central ovule-bearing part of the ovary arises separated from the carpel wall. The formation of ridges with teethlike appendages between the ovules suggests a derivation of the free-central placentation from an axile arrangement. Several characters support the monotypic family Coridaceae near the Primulaceae. Key words: Coridaceae, Primulaceae, Lythraceae, floral development, floral vasculature, epica...

Research paper thumbnail of Systematic significance of fruit morphology and anatomy in tribes Persicarieae and Polygoneae (Polygonaceae)

Botanical Journal of the Linnean Society, 2000

Research paper thumbnail of Dédoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

Botanical Journal of the Linnean Society, 1993

Research paper thumbnail of Floral Development of Three Maesa Species, with Special Emphasis on the Position of the Genus within Primulales

Research paper thumbnail of Floral Development and Anatomy ofMoringa oleifera(Moringaceae): What is the Evidence for a Capparalean or Sapindalean Affinity?

Research paper thumbnail of Floral Development of Cochlospermum tinctorium and Bixa orellana with Special Emphasis on the Androecium

American Journal of Botany, 1989

Research paper thumbnail of The floral development of Pleuropetalum darwinii, an anomalous member of the Amaranthaceae

Research paper thumbnail of D�doublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

Research paper thumbnail of Floral Development of Galopina tomentosa with a Discussion of Sympetaly and Placentation in the Rubiaceae

Systematics and Geography of Plants, 2000

Page 1. Syst. Geogr. Pl. 70: 155-170 (2000) Floral development of Galopina tomentosa with a discu... more Page 1. Syst. Geogr. Pl. 70: 155-170 (2000) Floral development of Galopina tomentosa with a discussion of sympetaly and placentation in the Rubiaceae Louis P. Ronse Decraene* & Erik F. Smets ... 15. Lateral view of older bud with differentiation of the anthers. ...

Research paper thumbnail of On the Wood and Stem Anatomy of Monococcus echinophorus (Phytolaccaceae s.l.)

Systematics and Geography of Plants, 2000

ABSTRACT Wood of the Australian monotypic genus Monococcus is characterised by short, narrow vess... more ABSTRACT Wood of the Australian monotypic genus Monococcus is characterised by short, narrow vessel elements, simple and non-bordered perforation plates, alternate vessel pitting, short fibres with vestigial pit borders, scanty axial parenchyma, and multiseriate rays mainly composed of upright/square ray cells. Styloids are most abundantly present in the secondary phloem. Moreover, secondary growth produced by successive cambia occurs in woody stem parts. These data are compared to other Phytolaccaceae s.l. and a close relationship between Monococcus, Rivina and Petiveria (Rivinoideae or Rivinaceae) is confirmed. However, data on a wider range of taxa are required to support a separation of Rivinaceae from Phytolaccaceae s.s. on the basis of stem anatomy. The presence or absence of successive cambia represents useful taxonomic information for evaluating phylogenetic relationships in Phytolaccaceae s.l. and Caryophyllales.

Research paper thumbnail of Staminodes: Their morphological and evolutionary significance

The Botanical Review, 2001

Research paper thumbnail of Theligonum cynocrambe: Developmental morphology of a peculiar rubiaceous herb

Plant Systematics and Evolution, 1998

Research paper thumbnail of Floral ontogeny and anatomy inKoelreuteria with special emphasis on monosymmetry and septal cavities

Plant Systematics and Evolution, 2000

... sepal 4 (cf. Radlkofer 1897: "schiefe Symmetrie"; Eichler 1878: "schr~ge Zygom... more ... sepal 4 (cf. Radlkofer 1897: "schiefe Symmetrie"; Eichler 1878: "schr~ge Zygomorphie") and differs from the current pattern with the symmetry line more or less crossing the median plane (median zygomorphy). Oblique zygo ...

Research paper thumbnail of Ontogeny and evolution of the flowers of South African Restionaceae with special emphasis on the gynoecium

Plant Systematics and Evolution, 2002

ABSTRACT . The South African Restionaceae make up a highly diverse group of genera displaying sev... more ABSTRACT . The South African Restionaceae make up a highly diverse group of genera displaying several reductive trends in the configuration of the flower, especially in the gynoecium. In this paper the floral ontogeny of fourteen species representing nine of the 11 genera of the Restio clade is studied with the SEM. Although flowers are basically simple, the variability in both mature and developmental stages is striking. Differences between species are the result of changes in growth rate, coupled with differential pressures of organs. Trends in the elaboration of bracts, perianth, androecium and gynoecium are compared. Together with data that have been presented elsewhere about the other clade of African Restionaceae, viz. the Willdenowia-clade, a scheme with potential developmental pathways is proposed and the most evident routes are selected based on ontogenetic evidence. Nine possible reductions are presented arising through three main routes.

Research paper thumbnail of Complex polyandry in the Magnoliatae: definition, distribution and systematic value

Nordic Journal of Botany, 1992

ABSTRACT A revised definition of complex polyandry is presented for the Magnoliatae. The differen... more ABSTRACT A revised definition of complex polyandry is presented for the Magnoliatae. The differences between primary polyandry and secondary (complex) polyandry are clarified. Fascicled stamens are probably not primitive in Magnoliatae. Complex polyandry finds its origin by an increase of stamens in an oligandrous framework. Multiplications of stamens occur either on primary complex primordia, which follow the regular phyllotactic sequence in the flower, either on a girdling primordium (ringwall). The primary primordia may be fully developed before a secondary proliferation of stamens takes place or provide room for more stamens by a continuing growth process. This happens by the development of a staminal tube (e.g. Malvales) or by the growth of a hypanthium (e.g. Myrtales). A typical floral vasculature is developed concomitantly with complex polyandry. Stamen trunk bundles (stamen fascicle traces) are correlated with preformed complex primordia and the absence of a hypanthium. The inception of a ringwall is responsible for a higher complexity in vasculature and for obscuring the identity of the trunk bundles. The presence of a hypanthium does not permit trunk bundle formation because stamens develop on a limited section of the hypanthial slope. In that case the vasculature is characteristically represented by few large bundles linked with the perianth and the androecium. The distribution of complex polyandry is plotted on a Dahlgrenogram and presented in a table. The systematic relevance of complex polyandry is limited to the lower taxonomic (e.g. familial) levels.

Research paper thumbnail of A floral ontogenetic investigation of the Hydrangeaceae

Nordic Journal of Botany, 1997

As a first step towards a broader floral ontogenetic study on Cornales, the flowers of four speci... more As a first step towards a broader floral ontogenetic study on Cornales, the flowers of four species of Hydrangeaceae (Deutzia corymbosa, Kirengeshoma palmata, Philadelphus purpurascens and Hydrangea petiolaris) were studied. In Deutzia and Kirengeshoma five sepal primordia are generally initiated, in Philadelphus only four. Sepal initiation in Kirengeshoma shows a tendency to tetramony. Deutzia has a variable sepal initiation. Petal growth was never retarded in the studied species. Initiation of the androecium in Kirengeshoma, Philadelphus and Hydrangea starts with antesepalous primary primordia, on which secondary primordia are soon formed, leading ultimately to the formation of polystaminate androecia. In Deutzia a diplostemonous androecium is formed, starting with the initiation of the antesepalous stamen primordia. Gynoecium development is similar in all species studied: on a concave floral apex, a ring meristem is initiated; it develops into a variable number of continuous carpel primordia, while the centripetally growing common margins form the septa. Initiation of the ovule primordia starts halfway up each placenta and extends in an apical, basal and lateral direction. A number of morphological problems are discussed, such as the derivation of tetramery, and evolutionary and developmental trends in the androecium and gynoecium. Kirengeshoma is well settled in Hydrangeaceae, although its exact position within the family remains uncertain. A sistergroup relationship of Hydrangeaceae with Loasaceae is supported. However, Hydrangeaceae also share features with Saxifragaceae (e.g. similar gynoecium development).

Research paper thumbnail of The floral development of Popowia whitei (Annonaceae)

Nordic Journal of Botany, 1990

ABSTRACT A study of the floral ontogeny of Popowia was carried out to investigate the phyllotacti... more ABSTRACT 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 androecium is initiated centripetally in successive whorls. A first whorl of three pairs of outer staminodes emerges opposite the outer petals and is followed by nine staminodes. Next a whorl of nine fertile stamens arises in alternation with the second whorl of staminodes. The carpels arise in three alternating whorls of nine. The nature of the perianth parts is morphologically identical. The process of cyclisation of the androecium from a spiral is discussed for Annonaceae and Magnoliidae in general. The inception of the three outer stamen pairs is a widespread reductive step for multistaminate androecia in the process of oligomerization. It is proposed to define the cyclic inception of numerous stamens as whorled polyandry, being an intermediate step between true polyandry and a reduced stamen number in whorls. The absence of a cup-like shape in the carpel development is related to the flattened receptacle.

Research paper thumbnail of Pseudodiplostemony, and its implications for the evolution of the androecium in the Caryophyllaceae

Journal of Plant Research, 1998

Research paper thumbnail of Floral Ontogenetic Evidence in Support of the Willdenowia Clade of South African Restionaceae

Journal of Plant Research, 2001

Research paper thumbnail of Similarities in Floral Ontogeny and Anatomy between the Genera Francoa (Francoaceae) and Greyia (Greyiaceae)

International Journal of Plant Sciences, 1999

A comparative study of the floral ontogeny and anatomy of Francoa, with one species, and Greyia, ... more A comparative study of the floral ontogeny and anatomy of Francoa, with one species, and Greyia, with three species, is made. Flowers arise nearly synchronously on terminal raceme‐like inflorescences with abortive growing tip. In Greyia, development of flowers shows a tendency toward monosymmetry, expressed in the initiation sequence of floral organs. Both genera are weakly obdiplostemonous by a later displacement of antepetalous stamens (“secondary obdiplostemony”), and they develop a comparable semi‐inferior, strongly grooved ovary with axile placentation. The staminodial nature of nectaries is rejected for both genera. The floral ontogenetic, anatomical, and morphological similarities of the two genera are obvious and are consistent with the proposal for a close relationship between Greyia and Francoa supported by molecular data.

Research paper thumbnail of The floral development and floral anatomy of Coris monspeliensis

Canadian Journal of Botany, 1995

The floral development of Coris was investigated to clarify its controversial relationship with e... more 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 with unilateral development encloses an actinomorphic flower. The stamen–petal tube has two sections that arise through three growth processes: a lower common part for stamens and petals and an upper section representing a fused corolla. The central ovule-bearing part of the ovary arises separated from the carpel wall. The formation of ridges with teethlike appendages between the ovules suggests a derivation of the free-central placentation from an axile arrangement. Several characters support the monotypic family Coridaceae near the Primulaceae. Key words: Coridaceae, Primulaceae, Lythraceae, floral development, floral vasculature, epica...

Research paper thumbnail of Systematic significance of fruit morphology and anatomy in tribes Persicarieae and Polygoneae (Polygonaceae)

Botanical Journal of the Linnean Society, 2000

Research paper thumbnail of Dédoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

Botanical Journal of the Linnean Society, 1993