Gynoecial morphology and funicular germination plugs in the Nolanaceae

In Nolana humifusa (Gouan) Johnst. and N. paradoxa Lindl, five carpel primordia unite by their thin margins to form the gynoecium wall. An ovule primordium is initiated in each of a maximum of six depressions, formed in the adaxial surface of each carpel primordium. The depressions become deeper, each developing into a duct that ends in an ovule chamber, which is a uniovulate locellus. The locellus is delimited by a ventral carpellary epidermis except at its lower adaxial part, where the ovule is invaginated on a short funicle from its own placenta.
Periclinal cell divisions in the subsurface layers of the floral apex form a receptacular column, which grows in continuity with the lower adaxial parts of the carpel primordia; the upper parts of the carpel primordia face the five-radiate "common cavity" inside the gynoecium wall. At anthesis this cavity is filled with stylar and ovarian transmitting tissue. The latter forms five "wings" that downward are continuous with wings of the receptacular column and which together with them radiate between the five carpels. True septa are not formed.
In N. humifusa a plurilocellate mericarp originates from each carpel primordium. In N. paradoxa longitudinal unilocellate portions of each plurilocellate carpel primordium develop independently into "carpel-lobes", the bulging lower parts of which mature into unilocellate mericarps. In both species the funicle develops into a germination plug.
The locellar organization described is a common feature of the Nolanaceae. The formation of invariably uniovulate placentae in pluriovulate carpels is the basic innovation of the family.     

ANATOMY OF THE GYNOECIUM IN TWO SPECIES OF BAKERIDESIA (MALVACEAE)

Structure of the gynoecium is described in two species of Bakeridesia, subgenus Bakeridesia (Malvaceae, tribe Malveae). The dorsal wall of each carpel bears a winglike projection with a marginal pair of pubescent, bluntly dentate wings. The projection arises as a single, solid ridge of tissue after the ovules are initiated and after the ventral carpellary margins are fused with the receptacle. Two multiseriate layers of fiber-sclereids line each locule and continue into the winglike projection where they are separated by parenchyma. Gynoecial vascularization is described in detail. The richly vascularized carpels are supplied by five traces: a median dorsal trace, which bifurcates into two dorsal bundles; two lateral traces; and two ventral traces. Adjacent ventral traces, lateral traces, and septal bundles are fused—i.e., they are held in common by neighboring carpels. The presence of lateral carpellary traces may be a primitive character in the tribe Malveae.     

GYNOECIAL ONTOGENY AND MORPHOLOGY,AND POLLEN TUBE PATHWAY IN BLACK MAPLE,ACER SACCHARUM SSP. NIGRUM (ACERACEAE)

The black maple (Acer saccharum Marsh, ssp. nigrum [Michx. f.] Desm.) gynoecium displays classical involute carpel development; carpels form, in mid- to late-summer, as two separate, opposite, hood-shaped primordia bearing naked megasporangia on inrolled carpel margins. Megasporogenesis, integument initiation, and carpel closure occur in spring; carpels fuse, forming a biloculate ovary with a short, hollow style and two divergent, dry, unicellular papillose stigmas. Transmitting tissues consist of developmentally and morphologically similar trichomes that form along the apparent carpel margins. The path from stigma to micropyle is open, but pollen tubes do not grow entirely ectotrophically. Germinating at the tip of a stigma papilla, a tube grows, apparently under the cuticle, to the papilla base. It then grows between stigma cells to the style, emerging to grow ectotrophically through the style to the compitum, where it passes into one of the locules. Within a locule, the tube grows over placenta and obturator to the micropyle, then between megasporangium cells to the female gametophyte, spreading over the surface near the egg. This study adds to our sparse understanding of gynoecium development and transmitting tissue in relation to pollen tube growth in naturally pollinated woody plants.     

Gynoecium evolution in angiosperms: Monomery,pseudomonomery, and mixomery

The presence of a gynoecium composed of carpels is a key feature of angiosperms. The carpel is often regarded as a homologue of the gymnosperm megasporophyll (that is, an ovule-bearing leaf), but higher complexity of the morphological nature of carpel cannot be ruled out. Angiosperm carpels can fuse to form a syncarpous gynoecium. A syncarpous gynoecium usually includes a well-developed compitum, an area where the pollen tube transmitting tracts of individual carpels unite to enable the transition of pollen tubes from one carpel to another. This phenomenon is a precondition to the emergence of carpel dimorphism manifested as the absence of a functional stigma or fertile ovules in part of the carpels. Pseudomonomery, which is characterized by the presence of a fertile ovule (or ovules) in one carpel only, is a specific case of carpel dimorphism. A pseudomonomerous gynoecium usually has a single plane of symmetry and is likely to share certain features of the regulation of morphogenesis with the monosymmetric perianth and androecium. A genuine monomerous gynoecium consists of a single carpel. Syncarpous gynoecia can be abruptly transformed into monomerous gynoecia in the course of evolution or undergo sterilization and gradual reduction of some carpels. Partial or nearly complete loss of carpel individuality that precludes the assignment of an ovule (or ovules) to an individual carpel is observed in a specific group of gynoecia. We termed this phenomenon mixomery, since it should be distinguished from pseudomonomery.     

Regulation of gynoecium marginal tissue formation by LEUNIG and AINTEGUMENTA

The carpel is the female reproductive organ of flowering plants. In Arabidopsis, congenital fusion of two carpels leads to the formation of an enclosed gynoecium. The margins of the two fused carpels are meristematic in nature and give rise to placentas, ovules, septa, abaxial repla, and the majority of the stylar and stigmatic tissues. Thus, understanding how the marginal tissues are specified and identifying genes that direct their development may provide important insight into higher plant reproductive development. In this study, we show that LEUNIG and AINTEGUMENTA are two critical regulators of marginal tissue development. Double mutants of leunig aintegumenta fail to develop placentas, ovules, septa, stigma, and style. This effect is specific to the leunig aintegumenta double mutant and is not found in other double mutant combinations such as leunig apetala2 or aintegumenta apetala2. Additional analyses indicate that the absence of marginal tissues in leunig aintegumenta double mutants is not mediated by ectopic AGAMOUS. We propose that LEUNIG and AINTEGUMENTA act together to control the expression of common target genes that regulate cell proliferation associated with marginal tissue development.     

HISTOGENESIS OF THE ANDROECIUM AND GYNOECIUM IN DOWNINGIA BACIGALUPII

A histogenetic investigation of the synandrous androecium and syncarpous gynoecium in the flower of Downingia bacigalupii Weiler (Campanulaceae; Lobelioideae) was undertaken for the purpose of comparing the modes of initiation, early growth and fusion in these floral whorls with that reported previously for the perianth in this species. Stamens are initiated as separate organs from the second tunica layer and underlying corpus regions of the concave floral meristem. Subsequent growth of stamens involves apical and intercalary growth in length and rudimentary marginal growth in breadth. Tissues of the four microsporangia originate from hypodermal sporangial initial cells and the filament is formed by intercalary growth at the base of the anther. Lateral fusion of stamens is ontogenetic and involves cuticular fusion of adjacent epidermal layers. The two emergent carpel primordia arise as crescentic organs by periclinal divisions in the second tunica layer and corpus zones. Carpel primordia also undergo apical and intercalary growth in length as well as extensive marginal growth in breadth. Radial growth in carpels is mediated by an adaxial meristem which shows its greatest concentration of activity at the carpel margins. Carpel fusion appears to be partially ontogenetic accompanied by zonal growth. Closure of the stylar canal is by the formation of a transmitting tissue derived from the protodermal layers of the adaxial carpel surfaces. A discoid nectary is initiated around the base of the style and formation of the inferior ovary is by intercalary growth of the base of the concave floral bud. The two parietal placentae originate as longitudinal outgrowths from the walls of the floral cup. Ovule initiation is simultaneous at first and then intercalary during subsequent elongation of the ovary. The ovules are anatropous, unitegmic and tenuinucellate. Stamen and carpel procambium shows a slight delay in differentiation when compared to that reported for the perianth and bract, but in all other respects carpels resemble other floral organs in their patterns of histogenesis and early growth. Stamens diverge from the other floral organs in their early pattern of growth, but a consideration of all features of their histogenesis suggests an appendicular rather than an axial interpretation of these organs.     

CRABS CLAW and SPATULA, two Arabidopsis genes that control carpel development in parallel with AGAMOUS

To help understand the process of carpel morphogenesis, the roles of three carpel development genes have been partitioned genetically. Mutants of CRABS CLAW cause the gynoecium to develop into a wider but shorter structure, and the two carpels are unfused at the apex. Mutants of a second gene, SPATULA, show reduced growth of the style, stigma, and septum, and the transmitting tract is absent. Double mutants of crabs claw and spatula with homeotic mutants that develop ectopic carpels demonstrate that CRABS CLAW and SPATULA are necessary for, and inseparable from, carpel development, and that their action is negatively regulated by A and B organ identity genes. The third carpel gene studied, AGAMOUS, encodes C function that has been proposed to fully specify carpel identity. When AGAMOUS function is removed together with the A class gene APETALA2, however, the organs retain many carpelloid properties, suggesting that other genes are also involved. We show here that further mutant disruption of both CRABS CLAW and SPATULA function removes remaining carpelloid properties, revealing that the three genes together are necessary to generate the mature gynoecium. In particular, AGAMOUS is required to specify the identity of the carpel wall and to promote the stylar outgrowth at the apex, CRABS CLAW suppresses radial growth of the developing gynoecium but promotes its longitudinal growth, and SPATULA supports development of the carpel margins and tissues derived from them. The three genes mostly act independently, although there is genetic evidence that CRABS CLAW enhances AGAMOUS and SPATULA function.     

STUDIES ON THE FLORAL ANATOMY OF THE CUNONIACEAE

Twenty-two genera representing sixty-two species of Cunoniaceae and Davidsonia were examined with respect to floral anatomy. Sepals are vascularized by three traces with the lateral traces of adjacent sepals united. Pancheria is unique for the family with species in which the sepals are vascularized by a single, undivided bundle. Petals, when present, and stamens, are uniformly one-trace structures. A general tendency exists within the family for the principal floral bundles to unite in various ways, with fusions evident between calyx, corolla, and androecial vascular supplies. Carpel number ranges from two to five and the gynoecium is generally surrounded by a prominent disc. Gynoecia of Ceratopetalum and Pullea are “half-inferior.” The number of ovules per carpel locule ranges from one to numerous. Ventral carpel sutures range from open to completely sealed at the level of placentation. Carpels of the apocarpous genus Spiraeanthemum (incl. Acsmithia) are vascularized by a dorsal bundle and either three or four bundles constituting the ovular and wing vasculation in the ventral position, a condition unlike other members of the family. Ovules are supplied by the median ventral bundle. More advanced bicarpellate gynoecia within the family are predominately vascularized by a dorsal and two ventral bundles although a variable number of additional lateral wall traces may be present. A major trend exists toward fusion of the ventral bundles of adjacent carpels in the ovary of both bicarpellate and multicarpellate plants. At the base of the styles the fused ventral strands separate and extend along with the dorsal carpellary bundles into styles of adjacent carpels. In Pullea the ventral bundles terminate within the ovules. The united ventral carpellary bundles in Aphanopetalum, Gillbeea, and Aistopetalum lie in the plane of the septa separating adjacent carpels. Ovules are vascularized by traces originating from the vascular cylinder at the base of the gynoecium or by traces branching from the ventral bundles. Ovular traces in each carpel are united, or remain as discrete bundles, prior to entering the placenta. Tannin and druses are common throughout all floral parts. Although floral anatomy generally supports the position of Cunoniaceae near Saxifragaceae and Davidsoniaceae, the evolutionary relationship of the Cunoniaceae to the Dilleniaceae is uncertain.     

鹅掌楸属植物引导组织和花粉管生长

应用光学显微镜和常规石蜡切片技术研究了鹅掌楸属（ＬｉｒｉｏｄｅｎｄｒｏｎＬ．）两种植物雌蕊引导组织的分布和个体发育,引导组织是由心皮边缘或内表面的表皮细胞层或亚细胞层发育形成,是由一层细胞组成的连续层,覆盖干柱头、花柱道和珠柄的表面,引导组织的细胞形态学因其所在部位不同而有差异。在电境水平上研究了柱头和花柱引导组织的超微结构,引导组织细胞是分泌型的传递细胞,其分泌面发育了明显的壁内突,细胞质中富含内质网、多聚核糖体、各种小泡、高尔基体和线粒体,大液泡通常远离分泌面。文中还探讨了花粉管生长后引导组织的变化。     

STIGMA,STYLE, AND OBTURATOR OF ORNITHOGALUM CAUDATUM (LILIACEAE) AND THEIR FUNCTION IN THE REPRODUCTIVE PROCESS

Transmitting tissue in Ornithogalum is divided into three regions corresponding to classical divisions of the gynoecium: stigma, style, and ovary. The stigma differentiates from epidermal cells of the stylar apex. These cells form the stigmal papillae and have dense cytoplasm with abundant ER and lipid bodies. Papillae have walls with small transfer-ingrowths. At floral receptivity, papillae secrete a small amount of surface exudate. Epidermal cells of the style contain numerous spherosomes and have thin filaments of cytoplasm traversing the central vacuole. The stylar cortex is composed of 3-6 layers of parenchyma cells which contain numerous spherosomes and often have secondary vacuoles. Vascular tissue in the style consists of one collateral bundle in each lobe. Cells of the epidermal layer lining the stylar canal are secretory. They are initially vacuolate but fill progressively with dense cytoplasm as their secretory activity increases. Secretory activity occurs in three phases, each characterized by a particular organelle population and secretory product. At anthesis, the canal is filled with an exudate consisting of carbohydrate, protein, and lipid. In the ovary, the obturator differentiates from cells at the base of the funiculus and the tip of the carpel margins. It forms a pad of tissue which covers most of the former placenta. The obturator is secretory and produces a surface exudate. We believe our observations on Ornithogalum support the hypothesis that all transmitting tissue is of the same morphological origin and that it provides nutritive and chemotropic factors for pollen tube growth.     

Flower and fruit characters in the early-divergent lamiid family Metteniusaceae, with particular reference to the evolution of pseudomonomery

Evaluating the morphological relationships of angiosperm families that still remain unplaced in the current systems of classification is challenging because it requires comparative data across a broad phylogenetic range. The small neotropical family Metteniusaceae was recently placed within the lamiids, as sister to either the enigmatic Oncothecaceae or the clade (Boraginaceae + Gentianales + Lamiales + Solanales + Vahliaceae). We examined the development of two of the primary diagnostic traits of Metteniusaceae, the moniliform anthers and the unilocular gynoecium. The gynoecium is 5-carpellate, and contains two ovules with a massive, vascularized integument. Late sympetaly and unitegmic ovules support placement of Metteniusaceae in the lamiids. The 5-carpellate gynoecium is consistent with a sister-group relationship between Metteniusaceae and Oncothecaceae. The gynoecium of Metteniusaceae is unusual in that it is monosymmetric throughout ontogeny, which indicates pseudomonomery; the five carpel initials are congenitally fused by their margins and form a single locule; the two ovules develop from the two smallest and most poorly developed lateral carpels. Comparisons with other pseudomonomerous taxa allow us to propose division of the complex processes leading to pseudomonomery into eight characters, including carpel number and fusion, gynoecial symmetry, timing of carpel reduction, and number and position of nonfertile carpels.     

商陆科植物的子房结构观察

商陆科植物几种雌蕊类型的发育和结构进行了观察,结果表明,商陆科植物的心皮发生后,首先形成一个开放的心皮,开口在心皮的腹侧,开口的封闭都是由心皮边缘的：表皮细胞及表皮下的几层细胞的分裂和生长完成。单心皮雌蕊在子房封闭后不留任何痕迹,而多心皮雌蕊的心皮封闭后留下明显的封闭线。封闭线由栅栏组织状组织构成。栅栏组织状组织一直延伸到珠柄,在珠柄基部形成毛刷状结构。离生心皮的隔在子房的生长过程中生长很少,心皮的大部分是分离的;合生心皮的隔在心皮的生长过程中与心皮同步生长,心皮始终是合生的。成熟子房的结构基本相同,子房壁为薄壁细胞,除表皮以外其他细胞均无太：大区别。在子房外侧壁中均匀地分布有3～5个维管束,隔中有一个维管束。胚珠生于子房的基部腹侧。     

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.     

Morphology and development of the female flowers in Geonoma interrupta (Arecaceae)

Morphology and development of the female flowers in Geonoma interrupta are described and compared with other taxa within Arecaceae. Inflorescences are pleiothyrses. Cincinni are immersed in pits and arranged according to the Fibonacci pattern along the rachillae. The gynoecium is composed of three free carpels in early stages and later becomes pseudomonomerous. Two carpels are sterile; they develop to different degrees and are commonly unequal in size. The fertile carpel contains a single, crassinucellate, anatropous ovule. Styles are formed in each carpel. The style of the fertile carpel becomes basifixed as the ovary enlarges. The stigmas remain free and plicate during development and expose unicellular papillae at anthesis. Pollen tube transmitting tracts and a compitum are present in the ventral slits of the stigmas and the postgenitally united styles during anthesis. A septal nectary is formed by incomplete union of the flanks of the carpels at the base of the gynoecium, and nectar is secreted from an epithelium. It is suggested that in Geonoma as a whole, the attraction of pollinators to female flowers is due to a combination of nectar reward and partial mimicry of male flowers.     

Floral development of Cardiopteris,with emphasis on gynoecial structure and ovular morphology

Cardiopteris is unique in the expanded Cardiopteridaceae for several distinctive features, including its gynoecial structure and ovular morphology. We studied the floral development of Cardiopteris to clarify floral morphology and document floral development. Cardiopteris has three carpel primordia, which are separate at their tips but congenitally fused at their bases. The synascidiate zone (the fused proximal part) develops into the unilocular ovary; the three discrete carpel apices diverge in development: the apex of the adaxial carpel differentiates into a style and stigma, while the apices of the two lateral-abaxial carpels elongate and develop into a fleshy appendage only after fertilization. The ovules are attached to the lateral-abaxial carpels. At anthesis, the ovules are ategmic and orthotropous without funicles (morphologically undifferentiated). Functional differentiation occurs in the three carpels of Cardiopteris: the adaxial one is the site of pollination, while the lateral-abaxial two produce ovules. The ategmic orthotropous ovule is unusual in Cardiopteridaceae and is an apomorphy of Cardiopteris.     

Structure,ultrastructure, and histochemistry of the pollen tube pathway in the milkweed Asclepias exaltata L.

The structure of the gynoecium and pollen tube pathway in unpollinated and pollinated carpels of Asclepias exaltata L. has been characterized. Pollen tubes penetrate a dry-type stigma, grow intercellularly in a core of solid tissue in the upper style, and subsequently traverse a hollow stylar canal to the ovary where they grow across the placental epithelium to the ovule micropyles. The fine structural characteristics of transmitting cells of the solid style, stylar canal, and placental epithelium indicate a secretory function. Extracellular secretions staining positively for proteins, insoluble carbohydrates, and arabinogalactans/arabinogalactan proteins are present in the solid style, hollow stylar canal, ovary, and micropyle. Micropylar exudate is present subtending the extended cuticle of the embryo sac adjacent to the filiform apparatus of the synergids, providing ultrastructural evidence for a secretion arising from the angiosperm embryo sac.     

Zur Entwicklung des Gynoeceums beiBergenia cordifolia (Saxifragaceae)

Scanning electron microscopical investigations of flower buds of the perennial herbBergenia cordifolia (Haw.)A. Br. (Saxifragaceae) reveal a primitive gynoecium. During ontogenesis the margins of the carpel lamina transgress on the apical cone of the axis by meristem incorporation and finally fuse with the margins of the opposite carpel. These processes of meristem incorporation and fusion first lead to gamophylly and furthermore to carpel peltation, as is demonstrated by SEM-photographs (ring-shaped dike and common septum of the two carpels). As a result of carpel peltation, the lowest point of the septum deliminates the synascidiate zone. Above this point, the symplicate and, eventually, the plicate zone follows (vid. ventral suture). The margins of the carpel lamina merely touch each other without being coalesced. The preparation of a window in the carpel's dorsal side permits a look at a massive lateral placenta (Leinfellner 1951) developing the ovules. In the lower third—in lateral position at the placenta's margin—the first ovules are seen, the next ones follow in acropetal and basipetal direction, as well as to the periphery of the placenta.

     

Structure and development of the stigma, style and ovary of Caesalpinia pulcherrima (L.) Sw., post-anthesis, pre- and post-pollination

The stigma of Caesalpinia pulcherrima is crateriform. The crater continues as a slit-like canal through the style and into the ovary. Both crater and canal are lined by several layers of fusiform and thin-walled cells which are continuous in two narrow regions in the ovary. Postanthesis and before pollination, the middle lamella of cells lining the stigmatic crater and stylar transmitting tissue undergoes dissolution. This occurs in a progression down the style with cells separating partially or wholly from neighbours. Dissolution is initiated at intercellular junctions where wall fibrils loosen and variously-sized and -shaped holes appear. Cytoplasmic changes include increased dictyosome activity, increased rough and smooth endoplasmic reticulum at the periphery of cells and accumulation of electron opaque deposits at the plasma membrane. The crater fills with stigmatic fluid and the diameter of the stylar canal increases. Pollen germinates in the secretion-filled crater, and pollen tubes grow down the style between the cells of the transmitting tissue but do not enter the canal. They emerge at the entrance to the ovary cavity and grow over one or two narrow strips of ovarian transmitting tissue cells which are present throughout the length of the ovary close to the ovules. This ensures that tubes grow in close proximity to the micropyles.     

FLORAL DEVELOPMENT OF POTAMOGETON RICHARDSONII

The inception and development of the sterile floral appendages of Potamogeton richardsonii have been re-investigated with a refined dissection technique (Sattler, 1968) and improved microtechnical methods (Feder and O'Brien, 1968). The results obtained by Sattler (1965) are confirmed, i.e., the sterile appendages are initiated at the flanks of the floral apex before the stamen primordia are formed. Consequently, they may be homologized with tepals or perianth members, although in the mature flower they are inserted at the stamen connective, due to growth between and at the base of each developing tepal and stamen. Each carpel arises as a radial primordium which becomes peltate immediately after its inception. One ovule primordium is initiated at the cross-zone. The stigma becomes bilobed. A slight outgrowth develops at the abaxial side of the style. The floral apex has a two-layered tunica. The primordia of the tepals, carpels, and ovules arise by periclinal divisions in the second tunica layer, whereas the stamen primordia are initiated by periclinal divisions in the corpus and second tunica layer. Variation in floral pattern, especially with regard to the number of appendages, has been observed in flowers near the tip of the inflorescence axis.     

FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. II. SAXIFRAGOIDEAE AND ITEOIDEAE

The floral anatomy and morphology of 26 species from the Saxifragoideae and three from the Iteoideae are described and compared. The flowers of the Saxifragoideae are predominantly actinomorphic, partially epigynous and/or perigynous, and pentamerous, with two carpels which bear numerous ovules. There is usually some degree of independence between carpels, and the normally separate styles possess both a canal and transmitting tissue. Generally, staminodia are absent and nectariferous tissue, which is not vascularized, is present. The subfamily is characterized by large multicellular trichomes with globular, often glandular, heads. Placentation may be parietal, axile, or transitional between the two; parietal appears to be a derived condition in the subfamily. The vascular cylinder in the pedicel generally consists of several to many discrete bundles from which diverge ten compound traces at the base of the receptacle, leaving an inner cylinder of vascular strands that coalesce at a higher level into either as many ventral bundles as carpels or twice that number. In the former case, each ventral bundle consists of one-half of the vascular supply to each adjacent carpel and separates into individual ventral strands in the distal half of the ovary. The ventral bundles provide vascular traces to the ovules and, along with the dorsals, extend up the style to the stigma. Each trace diverging in a sepal plane typically supplies one or more carpel-wall bundles, a median sepal bundle, and a stamen bundle. Each petal-plane trace usually provides one or more carpel-wall bundles, a lateral trace to each adjacent sepal, a petal bundle and, in flowers with ten stamens, a stamen bundle. Dorsal carpel bundles are usually recognizable and may originate from traces in either perianth plane. While the position of Ribes remains problematical, its floral structure does not easily exclude it from the Saxifragoideae. Floral structure in the Iteoideae is remarkably similar to that in the Saxifragoideae, the main differences being a lesser degree of independence between carpels, generally narrower placentae with somewhat fewer ovules, and the presence of only unicellular, acutely pointed epidermal hairs as opposed to the relatively complex, multicellular trichomes prevalent in the Saxifragoideae.