Comparative floral structure and systematics in Crossosomatales (Crossosomataceae, Stachyuraceae, Staphyleaceae, Aphloiaceae, Geissolomataceae, Ixerbaceae, Strasburgeriaceae)

Floral structure of all putative families of Crossosomatales as suggested by molecular studies was comparatively studied. The seven comprise Crossosomataceae, Stachyuraceae, Staphyleaceae, Aphloiaceae, Geissolomataceae, Ixerbaceae, and Strasburgeriaceae. The entire clade (1) is highly supported by floral structure, also the clades (in sequence of diminishing structural support): Ixerbaceae/Strasburgeriaceae (2), Geissolomataceae/Ixerbaceae/Strasburgeriaceae (3), Aphloiaceae/Geissolomataceae/Ixerbaceae/Strasburgeriaceae (4), and Crossosomataceae/Stachyuraceae/Staphyleaceae (5). Among the prominent floral features of Crossosomatales (1) are solitary flowers, presence of a floral cup, imbricate sepals with outermost smaller than inner, pollen grains with horizontally extended endoapertures, shortly stalked gynoecium, postgenitally united carpel tips forming a compitum, stigmatic papillae two‐ or more‐cellular, ovary locules tapering upwards, long integuments forming zigzag micropyles, cell clusters with bundles of long yellow crystals, mucilage cells, seeds with smooth, sclerified testa and without a differentiated tegmen. Clade (2) is characterized by large flowers, petals forming a tight, pointed cone in bud, stamens with long, stout filaments and sagittate anthers, streamlined, conical gynoecium, antitropous ovules, rudimentary aril, lignified, unicellular, T‐shaped hairs and idioblasts with striate mucilaginous cell walls. Clade (3) is characterized by alternisepalous carpels, punctiform stigma formed by postgenitally united and twisted carpel tips, synascidiate ovary, only one or two pendant ovules per carpel, nectary recesses between androecium and gynoecium. Clade (4) is characterized by pronounced ‘pollen buds’. Clade (5) is characterized by polygamous or functionally unisexual flowers, x‐shaped anthers, free and follicular carpels (not in Stachyuraceae). Crossosomataceae and Aphloiaceae, although not retrieved as a clade in molecular studies, share several special floral features: polystemonous androecium; basifixed anthers without a connective protrusion; stigma with two more or less decurrent crests; camplyotropous ovules and reniform seeds; simple, disc‐shaped nectaries and absence of hairs. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147 , 1–46.     

Comparative floral structure and systematics in Ochnaceae s.l. (Ochnaceae,Quiinaceae and Medusagynaceae; Malpighiales)

Ochnaceae s.l. (Ochnaceae, Quiinaceae and Medusagynaceae), one of the well‐supported subclades of the large order Malpighiales retrieved so far in molecular phylogenetic studies, were comparatively studied with regard to floral structure using microtome section series and scanning electron microscopy (SEM). Floral morphology, anatomy and histology also strongly reflect this close relationship. Potential synapomorphies of the subclade include: flowers nectarless, sepals of different sizes within a flower, petals not retarded in development and forming the protective organs of advanced floral buds, petal aestivation contort, petals with three vascular traces, petals reflexed over the sepals and directed toward the pedicel, polystemony, anthers almost or completely basifixed, gynoecium often with more than five carpels, short gynophore present, styles separate for at least their uppermost part and radiating outwards, suction‐cup‐shaped stigmas, vasculature forming a dorsal band of bundles in the upper stylar region, gynoecium epidermis with large, radially elongate cells, ovules either weakly crassinucellar or incompletely tenuinucellar with an endothelium, abundance of tanniferous tissues and sclerenchyma in floral organs. The most strongly supported subclade of two of the three families in molecular analyses, Quiinaceae and Medusagynaceae, is also particularly well supported by floral structural features, including the presence of functionally and morphologically unisexual flowers, a massive thecal septum that persists after anther dehiscence, styles radiating outward from the ovary, two lateral ovules per carpel, positioned one above the other, conspicuous longitudinal ribs on the ovary wall at anthesis, and a ‘false endothelium’ on the nucellus at anthesis. Additionally, the group fits well in Malpighiales and further emphasizes the relationship of Malpighiales with Celastrales and Oxalidales, and thus the unity of the COM clade. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 299–392.     

Comparative floral structure and systematics of Pelagodoxa and Sommieria (Arecaceae)

Floral structure is compared in Pelagodoxa and Sommieria (Arecaceae, Arecoideae). Male flowers have three free, imbricate sepals, three basally congenitally united and apically valvate petals, and six stamens. Anthers are dorsifixed and dehiscence introrse. The sterile gynoecium is tricarpellate. Female flowers have three free, imbricate sepals and three free, imbricate petals, which are slightly fused with the sepals at the base. Four to six staminodes are congenitally united at the base and fused with the ovary for a short distance. The gynoecium is syncarpous. Carpels are almost equal in early development; later the gynoecium becomes pseudomonomerous. The three stigmatic branches are equally developed, apical and sessile. The carpels are (syn-)ascidiate up to the level of the placenta and (sym-)plicate above. Each carpel has one ovule, in the sterile carpels it is aborted at anthesis. The fertile ovule is erect up to anthesis and pendant afterwards because of the bulging out of the ovary. Pollen tube transmitting tracts (PTTT) encompass the secretory epidermis of the ventral slits of each carpel. Floral structure in Pelagodoxa and Sommieria supports the sister group relationship between the two genera suggested in recent molecular phylogenies and reflects their close relationships to a major clade of pseudomonomerous arecoid palms from the Indo-Pacific region.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 27–39.     

Comparative floral structure and systematics in Oxalidales (Oxalidaceae, Connaraceae, Brunelliaceae, Cephalotaceae, Cunoniaceae, Elaeocarpaceae, Tremandraceae)

Floral morphology, anatomy and histology were studied in representatives of all families of current Oxalidales, which were recently constituted as a result of molecular systematic studies by other authors, and are composed of families of different positions in traditional classifications (Oxalidaceae, Connaraceae, Brunelliaceae, Cephalotaceae, Cunoniaceae, Elaeocarpaceae, Tremandraceae). Two of the three pairs of sister (or nested) families that come out in molecular analyses are highly supported by floral structure: Oxalidaceae/Connaraceae and Elaeocarpaceae/Tremandraceae, whereas Cephalotaceae/Cunoniaceae are not especially similar at the level of Oxalidales. Oxalidaceae and Connaraceae share petals that are postgenitally united into a basal tube (although they are imbricate in both) but free at the insertion zone, stamens that are congenitally united at the base, uniseriate glandular hairs on the stamen filaments, and ovules that are hemianatropous to almost orthotropous. The sharing of a special type of sieve-tube plastids and of trimorphic heterostyly, studied by other authors, should also be mentioned. With Brunelliaceae, the two families share an androgynophore and nectaries at the base of the stamens in alternisepalous sectors. Elaeocarpaceae and Tremandraceae share buzz-pollinated flowers and a syndrome of features functionally connected with it. In addition, petals are larger than sepals in advanced bud, they are valvate, involute and enwrap part of the adjacent stamens, they have three vascular traces. Lignified hairs are common on the anthers and are found in the ovary locules and on the ovules (not lignified) of representatives of both families. Ovules have a chalazal appendage, and the inner integument is much thicker than the outer.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 321–381.     

FLORAL ANATOMY OF KRAMERIA LANCEOLATA

The anatomy of each of the series of floral organs of Krameria lanceolata was examined. The sepals are characterized by three main veins each, an undifferentiated mesophyll, and stomata on the upper epidermis. The fleshy petals are distinguished by their numerous veins as well as by palisade-like epidermal cells on the outer surface. The three partially united petals have each a single vein and long, narrow epidermal cells similar to those on other floral organs. The stamens are united at their bases and bear tetra-sporangiate, conical anthers. The gynoecium includes a sterile and a fertile carpel. In the receptacle the veins to the sepals and petals are separated by a wide gap; those to the petals and stamens, by a narrow gap. Anatomical characteristics of the flower dissociate Krameriaceae from the legumes with which they have frequently been thought to be allied.     

A SCANNING ELECTRON MICROSCOPIC STUDY ON THE INITIATION AND DEVELOPMENT OF FLORAL ORGANS OF BRASSICA NAPUS (CV. WESTAR)

The initiation and development of the floral organs of Brassica napus L. (cv. Westar) were examined using the scanning electron microscope. After transition of the vegetative apex into an inflorescence apex, flower primordia were initiated in a helical phyllotactic pattern. The sequence of initiation of the floral organs in a flower bud was that of sepals, stamens, petals and gynoecium. Of the four sepal primordia, the abaxial was initiated first, followed by the two lateral and finally the adaxial primordium. The four long stamens were initiated simultaneously in positions alternating with the sepals. The two short stamens were initiated basipetal to and outside the long stamens, and opposite the lateral sepals. The petals arose on either side of the two short stamens and the gynoecium was produced from the remainder of the apex. During development, the sepal primordia curved sharply at the tips and tightly enclosed the other organs. Stamen primordia developed tetralobed anthers at an early stage while filament elongation occurred just prior to anthesis. A unique pattern of bulbous cells was present on the abaxial surface of the anther. Growth of petal primordia lagged relative to the other floral organs but expansion was rapid prior to anthesis. The gynoecium primordium was characterized by an invagination early in development. At maturity, there was differentiation of a papillate stigma, an elongated style and a long ovary marked externally by sutures and divided internally by a septum. Distinct patterns of cuticular thickenings were observed on the abaxial and adaxial surfaces of the petals and stamens and on the surface of the style. The patterns were less obvious on the sepals and ovary. Stomata were present on both surfaces of the mature sepals, on the style and restricted areas on the abaxial surface of the anthers and nectaries but were absent from the petals, the adaxial surface of the stamens and the ovary. No hairs were present on any of the floral organs.     

Comparative floral structure and systematics in Celastrales (Celastraceae, Parnassiaceae, Lepidobotryaceae)

Floral morphology, anatomy and histology in the newly circumscribed order Celastrales, comprising Celastraceae, Parnassiaceae and Lepidobotryaceae are studied comparatively. Several genera of Celastraceae and Lepidobotrys (Lepidobotryaceae) were studied for the first time in this respect. Celastraceae are well supported as a group by floral structure (including genera that were in separate families in earlier classifications); they have dorsally bulged‐up locules (and thus apical septa) and contain oxalate druses in their floral tissues. The group of Celastraceae and Parnassiaceae is also well supported. They share completely syncarpous gynoecia with commissural stigmatic lobes (and strong concomitant development of the commissural vascular bundles but weak median carpel bundles), only weakly crassinucellar or incompletely tenuinucellar ovules with an endothelium, partly fringed sepals and petals, protandry in bisexual flowers combined with herkogamy by the movement of stamens and anther abscission, and stamens fused with the ovary. In contrast, Lepidobotryaceae are more distant from the other two families, sharing only a handful of features with Celastraceae (not Parnassiaceae), such as pseudohermaphroditic flowers, united stamen bases forming a collar around the gynoecium and seeds with a conspicuous aril. However, all three families together are also somewhat supported as a group and share petals that are not retarded in late floral bud development, 3‐carpellate gynoecia, ventral slits of carpels closed by long interlocking epidermal cells and pollen tube transmitting tissue encompassing several cell layers, both integuments usually more than two cell layers thick, and only weak or lacking floral indumentum. In some molecular analyses Celastrales form an unsupported clade with Malpighiales and Oxalidales. This association is supported by floral structure, especially between Celastrales and Malpighiales. Among Celastrales, Lepidobotryaceae especially share special features with Malpighiales, including a diplostemonous androecium with ten fertile stamens, epitropous ovules with an obturator and strong vascularization around the chalaza. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 149 , 129–194.     

The floral development and floral anatomy ofChrysosplenium alternifolium, an unusal member of the Saxifragaceae

The floral development and anatomy ofChrysosplenium alternifolium were studied with the scanning electron microscope and light microscope to understand the initiation sequence of the floral organs and the morphology of the flower, and to find suitable floral characters to interpret the systematic position of the genus within the Saxifragaceae. The tetramerous flower shows a highly variable initiation sequence. The median sepals and first stamens arise in a paired sequence resembling a dimerous arrangement, but the first sepal and stamen arise on the side opposite to the bract. Transversal sepals and stamens emerge sequentially, as one side often precedes the other; sepals and stamens occasionally arise on common primordia. Initiation of the gynoecium is more constant with two median carpel primordia arising on a sunken floral apex. Several flowers were found to be pentamerous with a 2/5 initiation sequence. Flowers were invariably found to be apetalous without traces of petals in primordial stages; this condition is interpreted as an apomorphy. It is postulated that the development of a broad gynoecial nectary is responsible for the occurrence of an obdiplostemonous androecium. The gynoecium shows a number of anatomical particularities not observed in other Saxifragaceae. The presence and distribution of colleters is discussed.     

Characterization of unisexual flower development in the endangered mahogany tree Swietenia macrophylla King. (Meliaceae)

The selection of candidate plus trees of desirable phenotypes from tropical forest trees and the rapid devastation of the natural environments in which these trees are found have created the need for a more detailed knowledge of the floral and reproductive biology of tropical tree species. In this article, the organogenic processes related to unisexual flower development in tropical mahogany, Swietenia macrophylla , are described. Mahogany inflorescences at different developmental stages were evaluated using scanning electron microscopy or optical microscopy of histological sections. The unisexual flowers of S. macrophylla are usually formed in a thyrse, in which the positions of the female and male flowers are not random. Differences between male and female flowers arise late during development. Both female and male flowers can only be structurally distinguished after stage 9, where ovule primordia development is arrested in male flowers and microspore development is aborted in female flower anthers. After this stage, male and female flowers can be distinguished by the naked eye as a result of differences in the dimensions of the gynoecium. The floral characteristics of S. macrophylla (distribution of male and female flowers within the inflorescence, and the relative number of male to female flowers) have practical implications for conservation strategies of this endangered species.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 529–535.     

FLORAL MORPHOLOGY,ORGANOGENESIS AND INTERPRETATION OF THE INFERIOR OVARY IN DOWNINGIA BACIGALUPII

The inflorescence of Downingia bacigalupii (Campanulaceae; Lobelioideae) is an indeterminate spike. Axillary flowers have a long, linear, inferior ovary with parietal placentation, a pentamerous synsepalous calyx, zygomorphic sympetalous corolla, syngenesious stamens, and a bicarpellate, syncarpous gynoecium. On the basis of floral vascular anatomy the inferior ovary is interpreted as appendicular, representing adnation of outer floral whorls to the gynoecium. Floral ontogeny shows that sepals are initiated in an adaxial to abaxial sequence rather than the 2/5 phyllotaxis reported for other members of Lobelioideae. Growth of the common bases of sepal lobes forms a floral cup and initiation of the following floral whorls occurs along the inner margins of the cup. Continued basal growth of the cup-shaped bud results in the formation of the elongated inferior ovary. Earlier evidence for the interpretation of a cup-shaped receptacle during development of epigynous flowers is reexamined and it is concluded that the concave floral bud of D. bacigalupii can also be interpreted as common growth of connate floral whorls, supporting interpretations based on vascular anatomy. Comparison of floral development between Downingia bacigalupii and Pereskia aculeata (Cactaceae) reveals ontogenetic differences between flowers with appendicular and receptacular cups.     

THE COMPARATIVE MORPHOLOGY OF THE CANELLACEAE. IV. FLORAL MORPHOLOGY AND CONCLUSIONS

The morphology and anatomy of 105 flowers representing 13 species and 6 genera of the Canellaceae are summarized. The flowers are borne in axillary or terminal racemes, cymes, or small groups, or solitary, in an axillary or terminal position. The flowers are characterized as follows: bisexual, hypogynous; sepals 3, thick and leathery; petals, 5–12, free or united into tube at base, rather thick, in 1 or 2 whorls and/or spirals; androecium of 6–12 stamens united by their filaments forming a tube, anthers with longitudinal extrorse dehiscence; gynoecium of 2–6 carpels fused by their ventral margins; 2–6 placentae. There are 2 vascular bundles (rarely 3) to each sepal, 3 to each petal (some of the inner petals have only 1), 1 to each stamen and 1 trace to each carpel. The petal and stamen bundles have a common origin. All the data accumulated in this series on the Canellaceae indicate that the correct systematic placement of the Canellaceae is in the woody Ranales, perhaps in a complex with the Myristicaceae.     

Flower morphology and relationships of Schefflera subintegra (Araliaceae,Apiales): an evolutionary step towards extreme floral polymery

Gross morphology and the development of flowers in Schefflera subintegra (Araliaceae) are examined. The floral groundplan of this species is found to be very similar to that of Tupidanthus calyptratus representing a case of most extreme floral polymery within Araliaceae. Schefflera subintegra differs from T. calyptratus with respect to a lower floral merism (19–43 versus 60–172 stamens and 15–33 versus 60–138 carpels respectively) and by transformation from polysymmetry to disymmetry of flower in the course of its development. Close relationships between S. subintegra, T. calyptratus, and Schefflera hemiepiphytica have been confirmed by phylogenetic analysis based on nuclear ribosomal internal transcribed spacer sequences. These species form a subclade within the Asian Schefflera clade, with T. calyptratus as a sister taxon to two other species. Apart from more or less pronounced floral polymery, the species of this subclade share calyx and corolla without any traits of individual sepals and petals, and also a massive calyptra. As these data suggest, the extremely polymerous flowers of Tupidanthus apparently evolved in two steps: (1) the saltational multiplication of floral elements together with a loss of individuality of sepals in the calyx and petals in the corolla and (2) further polymerization of androecium and gynoecium. Mutation(s) in CLAVATA‐like gene(s) are suggested as a possible mechanism of the saltation event. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 553–597.     

The gynostemium of Hemipiliopsis purpureopunctata and Senghasiella glaucifolia, two taxonomically disputed species of Habenariinae (Orchidaceae)

The gynostemium structure and ontogeny of two taxonomically disputed orchids, Hemipiliopsis (= Habenaria ) purpureopunctata and Senghasiella (= Habenaria ) glaucifolia , are described and illustrated by scanning electron micrographs. The early gynostemium ontogeny of Hemipiliopsis purpureopunctata is shown to be fundamentally similar to that of the species of the tribe Orchideae that have been previously studied. This includes the initiation sequence of sepals, petals and lip, form and orientation of anthers, three-lobed condition of median carpel apex, and presence of auricles and basal bulges. During the later developmental stages some differences occur. The stigma processes of Senghasiella glaucifolia are united into a tongue-shaped organ, and the lateral rostellum lobes of Hemipiliopsis purpureopunctata protrude forwards with their viscidia positioned above the spur-mouth. Based on gynostemium characters, the generic rank of Hemipiliopsis was confirmed, but that of Senghasiella was not supported.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 191–196.     

Homeotic, Meristic and Cytological Floral Mutants of Thryptomene calycina (family Myrtaceae)

Twenty plants with various phenotypic abnormalities to the flowerswere selected from very large populations of Thryptomene calycinain the Grampian and Black Ranges. Most of these had impairedreproductive function. Normal flowers were epigynous with fivesepals, five petals, five anthers, a single style and two anatropousovules. The mutants were two partially male sterile, tetraploidplants with large flowers, one of which occasionally producedadditional flowers from the leaf axils with peduncles as wellas pedicels; one plant which produced a proportion of hexapetaloidflowers with six stamens; three gross mutants with fleshy, bracteoidpointed petals and sepals, no stamens, vestigial styles andstigmas, exposed ovules and no inferior ovary; one plant withfleshly, bracteoid pointed sepals, vestigial style and stigmabut with exposed ovular structures replaced by four to fivesterile ovules generally inside an abnormal ovary; two plantswith reduced ovary diameter and sterile ovules, shortened style,five reduced sepals and petals and five to eight anthers; threeanthocyanin-free plants; three plants with pink sepals; twoplants with half-sized flowers which produced a proportion offasciated stems; one plant which occasionally produced flowerswithout pedicels which virtually resulted in organs which wereleaf-flower composites; two plants which produced sepals andpetals which contained chlorophyll and prematurely senesced,and had partial substitution of petals by anthers.Copyright1993, 1999 Academic Press Thryptomene calycina, Myrtaceae, Victorian lace flower, floral mutations, mutants, homeotic, meristic, tetraploid, fasciation, male sterility, cut flowers     

Comparative floral development in Lardizabalaceae (Ranunculales)

Lardizabalaceae, one of seven families of Ranunculales, represent a monophyletic group. The family has functionally unisexual flowers with the organs in trimerous whorls, petaloid sepals and sometimes nectariferous petals. Among Ranunculales, Lardizabalaceae share several floral characters and climbing habit with Menispermaceae, but molecular analyses indicate that Circaeasteraceae and Lardizabalaceae form a strongly supported clade. Morphological and ontogenetic studies of flowers have proved to be a good complement to molecular data in clarifying relationships. Floral organogenesis has been studied in very few species of the family. This study investigates the comparative floral development of three species from three genera (Decaisnea, Akebia and Holboellia) of Lardizabalaceae using scanning electron microscopy. Flowers have a whorled phyllotaxis. Within each whorl, the organs are initiated either simultaneously or in a rapid spiral sequence. In Akebia, six sepals are initiated, but one to three sepals of the second whorl do not further develop. The presence of three sepals in Akebia is thus a developmentally secondary simplification. The petals (if present) are retarded in early developmental stages; stamens and petals are different in shape from the beginning of development. The retarded petals may not be derived from staminodes in Lardizabalaceae. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 171–184.     

Fossil flowers of ericalean affinity from the Late Cretaceous of Southern Sweden

Charcoalified fossil flowers of a new genus and species (Paradinandra suecica) with affinities to Ericales s.l. (sensu lato) are described from the Late Cretaceous (Santonian-Campanian) from Southern Sweden. The flowers are pentamerous, hypogynous, and actinomorphic. Aestivation of sepals and petals is imbricate-quincuncial. The androecium consists of an outer whorl with single episepalous stamens and an inner whorl with paired epipetalous stamens. Pollen is small and probably tricolpate. Three carpels form a syncarpous ovary with numerous campylotropous ovules on parietal placentae. The styles are free for most of their length. The structure of mature fruits and seeds is unknown. Clear distinction of sepals and petals, possible dehiscence of anthers by restricted slits, presence of a nectary, and the general floral construction (salverform corolla) with a canalized access to the floral center clearly indicate insect pollination of the fossil flowers. Comparisons with extant taxa demonstrate that Paradinandra suecica shares many similarities with Ericales s.l. and in particular with members of Ternstroemiaceae, Theaceae, and Actinidiaceae. However, it is neither identical to any one genus of these families nor to any of the previously described ericalean taxa from the Cretaceous and thus provides further evidence of the diversity of Cretaceous ericalean plants.     

Intra‐individual variation of flowers in Gunnera subgenus Panke (Gunneraceae) and proposed apomorphies for Gunnerales

A study of inflorescence and flower development in 12 species from four of the six subgenera of Gunnera (Gunneraceae) was carried out. In the species of subgenus Panke, initiation of floral apices along the partial inflorescences is acropetal but ends up in the late formation of a terminal flower, forming a cyme at maturity. The terminal flower is the largest and the most complete in terms of merosity and number of whorls and thus it is the most diagnostic in terms of species‐level taxonomy. The lateral flowers undergo a basipetal gradient of organ reduction along the inflorescence, ranging from bisexual flowers (towards the distal region) to functionally (i.e. with staminodia) and structurally female flowers (towards the proximal region). Our results show that the terminal structure in Gunnera is a flower rather than a pseudanthium. The terminal flower is disymmetric, dimerous and bisexual, representing the common bauplan for Gunnera flowers. It has a differentiated perianth with two sepals and two alternate petals, the latter opposite the stamens and carpels. Comparisons with other members of the core eudicots with labile floral construction are addressed. We propose vegetative and floral putative synapomorphies for the sister‐group relationship between Gunneraceae and Myrothamnaceae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 262–283.     

FLORAL DEVELOPMENT IN MANGROVE RHIZOPHORACEAE

The flowers of mangrove Rhizophoraceae (tribe Rhizophoreae) are adapted to three different pollination mechanisms. Floral development of representative species of all four genera suggests that the ancestral flower of the tribe was unspecialized, with successively initiated whorls of separate sepals, petals, antisepalous stamens, and antipetalous stamens; at its inception, the gynoecium had a united, half-inferior ovary and separate stigmatic lobes. This developmental pattern is found in Rhizophora mangle (wind-pollinated) and Ceriops decandra (insect-pollinated). In Kandelia, all floral organs distal to the sepals are initiated simultaneously, and there has apparently been an evolutionary amplification in the number of stamens to about six times the number of petals. Explosive pollen release evolved independently in C. tagal and in Bruguiera. In the former, all stamens belong to one whorl and arise simultaneously upon a very weakly differentiated androecial ring primordium. In Bruguiera, the androecial ring is pronounced, and two whorls of stamens arise upon it; the primordia of the antisepalous whorl arise first but are closer to the center of the apex than the antipetalous stamen primordia. The antisepalous stamens bend toward and are enclosed by the petals early in development. In all genera, the inferior ovary develops by zonal growth of receptacular tissue; additional intercalary growth above the placenta occurs in Bruguiera. In general, floral specialization is accompanied by an increase in the width of the floral apex compared to the size of the primordia, increasing fusion of the stylar primordia, and decreasing prominence of the superior portion of the ovary. Apparent specializations of petal appendages for water storage, including the presence of sub-terminal hydathodes (previously unreported in any angiosperm), were found in two species in which flowers remain open during the day but were absent from two species normally pollinated at night or at dawn. Distinctive tribal characteristics that may aid in phylogenetic analysis include the mode of development of the inferior ovary; the aristate, bifid, usually fringed petals that individually enclose one or more stamens; the intrastaminal floral disc; and the initially subepidermal laticiferous cell layer in the sepals and ovary.     

Cunoniaceae in the Cretaceous of Europe: Evidence from Fossil Flowers

Fossil flowers of the Cunoniaceae from Late Cretaceous sedimentsof southern Sweden are described in detail. The flowers aresmall, bisexual, actinomorphic, tetramerous with broadly attachedvalvate sepals; they have narrowly attached petals; eight stamensin two whorls; a massive, lobed nectary; a semi-inferior, syncarpousgynoecium with axile placentation; numerous ovules; separatestyles; and peltate, probably secretory, trichomes. They sharemany features with extant representatives of both the Cunoniaceaeand Anisophylleaceae. However, the gynoecium structure in particularindicates a closer relationship to the Cunoniaceae. The floralcharacters are not specific for any extant genus of the familyand therefore a new genus and species, Platydiscus peltatusgen. et sp. nov., is formally described. This is the first recordof cunoniaceous floral structures from the Northern Hemisphereand the oldest record of Cunoniaceae flowers worldwide. Copyright2001 Annals of Botany Company Anisophylleaceae, Cunoniaceae, fossil flowers, Late Cretaceous, Oxalidales, Platydiscus peltatus gen. et sp. nov., Santonian-Campanian, southern Sweden     

Comparative floral structure and systematics in Rhizophoraceae,Erythroxylaceae and the potentially related Ctenolophonaceae,Linaceae, Irvingiaceae and Caryocaraceae (Malpighiales)

Within the rosid order Malpighiales, Rhizophoraceae and Erythroxylaceae (1) are strongly supported as sisters in molecular phylogenetic studies and possibly form a clade with either Ctenolophonaceae (2) or with Linaceae, Irvingiaceae and Caryocaraceae (less well supported) (3). In order to assess the validity of these relationships from a floral structural point of view, these families are comparatively studied for the first time in terms of their floral morphology, anatomy and histology. Overall floral structure reflects the molecular results quite well and Rhizophoraceae and Erythroxylaceae are well supported as closely related. Ctenolophonaceae share some unusual floral features (potential synapomorphies) with Rhizophoraceae and Erythroxylaceae. In contrast, Linaceae, Irvingiaceae and Caryocaraceae are not clearly supported as a clade, or as closely related to Rhizophoraceae and Erythroxylaceae, as their shared features are probably mainly symplesiomorphies at the level of Malpighiales or a (still undefined) larger subclade of Malpighales, rather than synapomorphies. Rhizophoraceae and Erythroxylaceae share (among other features) conduplicate petals enwrapping stamens in bud, antepetalous stamens longer than antesepalous ones, a nectariferous androecial tube with attachment of the two stamen whorls at different positions: one whorl on the rim, the other below the rim of the tube, the ovary shortly and abruptly dorsally bulged and the presence of a layer of idioblasts (laticifers?) in the sepals and ovaries. Ctenolophonaceae share with Rhizophoraceae and/or Erythroxylaceae (among other features) sepals with less than three vascular traces, a short androgynophore, an ovary septum thin and severed or completely disintegrating during development, leading to a developmentally secondarily unilocular ovary, a zigzag‐shaped micropyle and seeds with an aril. Special features occurring in families of all three groupings studied here are, for example, synsepaly, petals not retarded and thus forming protective organs in floral bud, petals postgenitally fused or hooked together in bud, androecial tube and petals fusing above floral base, androecial corona, apocarpous unifacial styles, nucellus thin and long, early disintegrating (before embryo sac is mature), and nectaries on the androecial tube. Some of these features may be synapomorphies for the entire group, if it forms a supported clade in future molecular studies, or for subgroups thereof. Others may be plesiomorphies, as they also occur in other Malpighiales or also in Celastrales or Oxalidales (COM clade). The occurrence of these features within the COM clade is also discussed. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 331–416.