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Leaves of representative taxa within the vanilloid clade of Orchidaceae were cleared and their venation patterns studied. Within subtribe Pogoniinae, Isotria and Pogonia exhibit a prominent reticulate venation pattern, although only Pogonia ophioglossoides is characterized by free vein endings. Within subtribe Vanillinae, all species of Epistephium , as well as the New Caledonian endemics, Eriaxis rigida and Clematepistephium smilacifolium , have reticulate-veined leaves that are characterized by numerous free vein endings. Leaves of most species of Vanilla exhibit a parallel-veined pattern stereotypical of monocots, although branched secondaries with free endings were observed in V. africana . Most members of subtribe Galeolinae are «saprophytes» with reduced bract-like leaves. Vascular bundles enter these leaf-homologues in a parallel manner, but quickly ramify throughout the tissue in an irregular manner. Leaf venation is used to hypothesize patterns of generic relationships within the vanilloid clade. Molecular evidence for phylogenetic relationships among angiosperms indicates that reticulate leaf venation has arisen independently in several unrelated monocot families, including the vanilloid Orchidaceae, perhaps by a similar evolutionary scenario.

A comprehensive study of the nodal and leaf anatomy of Bonnetiaceae was completed in order to provide evidence for evaluation in relation to systematics. Nodal anatomy is trilacunar, three-trace or unilacunar, one-trace. Basic leaf anatomical features of the family include: complete or incomplete medullated vascular cylinder in petiole; paracytic mature stomata with encircling ridges; large mucilaginous cells in the adaxial surface of mesophyll; periclinal divisions in upper surface layers; and discrete patches of phloem within the vascular bundles. Especially noteworthy is the presence in some genera of foliar vascular bundles enveloped by a sheath composed of two concentric regions, i.e., an inner region consisting of multiple layers of fibers and an outer specialized endodermis composed of thin-walled cells with Casparian strips. Leaves are variable with respect to lamina and cuticle thickness, relative amount and number of palisade and spongy layers, venation of lamina, and the presence or absence of sclereids and crystals in the mesophyll. A major feature in the evolution of Bonnetiaceae is development of a highly divergent, essentially parallel, leaf venation that is superficially similar to that of some monocotyledons and apparently unique among dicotyledons. Foliar anatomy provides important characters for the recognition of subgroups within Bonnetiaceae and is consistent with the segregation of Bonnetiaceae from Theaceae.

Summary was undertaken in an attempt to help clarify the relationships of the genus. Detailed descriptions of leaf, stem, nodal, wood, and floral anatomy are presented. Wood is characterized by a combination of solitary and grouped vessels with elements having few-barred scalariform perforation plates, imperforate tracheary elements with very reduced pit borders, exceptionally tall and broad hetero- cellular rays, and vasicentric axial parenchyma. Of special interest is the presence in Sanango of a very uncommon multilacunar nodal structure having split-lateral traces. Stems possess cortical vascular bundles. Leaf stomata are anisocytic and distributed in clusters on the undersurface of the lamina. Anatomical evidences suggest that Sanango is most closely related to the Scrophulariales, sharing many important features with the Gesneriaceae.

The floral and vegetative anatomy of the small Australian genus Aphanopetalum were studied. Wood is described for the first time and is characterized by predominantly solitary pores, scalariform vessel element perforation plates with low bar numbers, imperforate tracheary elements with distinctly bordered pits, sparse axial parenchyma, and a combination of homocellular and heterocellular rays. Starch occurs in both axial and ray parenchyma of the wood. Stems possess unilacunar, one-trace nodes and the uncommon feature of an endodermis with well-defined Casparian strips. Leaves have anomocytic stomata, a bifacial mesophyll and semicraspedodromous venation or a combination of semicraspedodromous and brochidodromous venation. The tetramerous flowers are apetalous or have minute petals. The compound, half-inferior gynoecium consists of essentially totally united carpels. The pattern of floral vascularization resembles different Saxifragaceae sensu lato in that the compound sepal-plane and petal-plane traces give rise to staman bundles as well as sepal, petal, and carpel wall venation in their respective planes. The ventral ovarian bundles are fused into a single ventral complex that subdivides at the top of the ovary to form ventral bundles and to supply the one ovule in each locule. Vegetative and floral features provide compelling evidence to suggest that Aphanopetalum has its nearest relatives among the Saxifragaceae sensu lato rather than Cunoniaceae. The genus is probably best treated as forming its own subfamily (or family) among the saxifragaean alliance.

All eleven genera of the Styracaceae were examined with respect to floral morphology and anatomy. Floral structure and vascularization are described in detail. Flowers of the family exhibit different degrees and patterns of specialization. All Styracaceae show some degree of basal non-divergence of perianth members, forming a hypanthium that is adnate to the ovary wall to a lesser or greater extent. The extent of reduction and amplification in the number of sepals, petals, stamens, and carpels varies widely among genera, and generally the non-divergence, decrease, or increase in parts is not equally pronounced in the different whorls of the same sower. Genera cannot be readily aligned in an intergrading sequence of morphological advancement. Stamen form and anatomy is variable. A fibrous endothecium ranges from well-developed to weakly formed or absent. A nearly uniform feature of the styracaceous gynoccium is the presence of incompletely septate ovaries. The major points of variation in the floral vascular system relate to the number, mode of origin, and degree of independence of sepallary traces; degree of independence of the androecial vasculature; the level at which the common petal and petaladstamen or sepal and sepalad-stamen bundles separate to their component parts; organization of the ventral ovarian supply; and the occurrence of ventral bundles in the style. Floral vascularization provides evidence that the family was derived from an obdiplostemonous ancestor. A unitegmic ovule is predominant in the family and starch is present in the megagametophyte of some taxa. An unusual feature of the flowers of the Styracaceae is the occurrence of stellate and lignified intraovarian trichomes. Numerous similarities in floral morphology and anatomy between Styracaceae and Ericales are pointed out.

Pollen representing twenty-three species in all eleven genera of Styracaceae was examined by combined light, scanning and transmission electron microscopy. A comparative examination of the morphological features of the grains was conducted in an attempt to evaluate the importance of pollen morphology to the systematics of the family. Pollen morphology of the Styracaceae is rather uniform, with few variable features. Grains of nearly all examined species are solitary, mediumsized, radially symmetrical, tricolporate with lalongate endoapertures each with an equatorial bridge, and a tectate-perforate-columellate exine. The stratified exine has four consistent layers, including a well-developed tectum and an endexine that is often internally thinly fragmented along the mesocolpi and thickened under the colpi. Although the pollen of the family is relatively uniform, subtle variation is present, particularly in sculpturing type, where intertwined rugulate-reticulate, transitional fossulate-foveolate, f...

The comparative vegetative and reproductive morphology and anatomy of the endangered, monotypic, dicotyledonous genusMedusagyne was studied, and detailed descriptions of leaf, axis, nodal, wood, floral, pollen, fruit, and seed structure are presented. Overall, the genus has many specialized features, including the possession of extreme, habitat-related specializations. Flowers are either bisexual or staminate, and are interpreted as retaining some primitive aspects, such as many free parts spirally arranged on an elongate floral axis. One of the most salient structural features of the plant is the massive development of ensheathing fibrous elements around the vascular system of both vegetative and reproductive tissues. Diffuse foliar sclereids are absent. Particular attention is paid to the unusual multicarpellate, synovarial gynoecium and comparisons are made with theCaryocaraceae. The totality of morphological and anatomical evidence confirms the view thatMedusagyne is a very distinct and evolutionarily isolated genus, best treated as forming the monotypic familyMedusagynaceae. Observations are presented, including the occurrence of stamen fascicle traces, that link the family to the dillenialean and thealean assemblage. Like other isolated thealean taxa,Medusagyne shows affinities to several different families, without having especially close relationships with any particular extant taxon.

The plant body of a typical angiosperm consists of two major organ systems: the root and the shoot. The shoot is composed of stems, leaves, and flowers, and each major organ in turn is composed of tissues that represent collections of one or more specialized cell types. All growth and organ formation of the plant body are initiated and controlled by regions of active cell division termed “meristems.” Meristems are composed of two categories of cells: the dividing initials and the immediate undifferentiated derivatives of cell division. The derivatives subsequently become differentiated and change into different types of mature cells and tissues. Following fertilization, the plant body begins development as a single-celled zygote that undergoes embryogenesis. After a series of early cell divisions, a globose proembryo is formed. During the later stages of embryo development, the embryonic axis of the plant body is formed along with the root and shoot apical meristems from which the rest of the plant body develops following seed germination. One of the most distinctive structural features of plant cells is the surrounding cell wall, typically composed of carbohydrate cellulose. Cell walls play important roles in plant development, cell-to-cell communication, physiology and environmental adaptation, and stress response.

Plants carry out numerous complex processes constituting their physiology to maintain themselves as living systems. Many of these physiological processes are closely related to plant structure. The basic activities are photosynthesis, respiration, metabolism, nutrition, and translocation and mobilization of water and photosynthetic solutes. The principal functional units of the phloem tissue of flowering plants include the major conducting conduit called the sieve tube element, along with its associated companion cells and a variety of integrating phloem parenchyma cells. The structure of the minor veins plays an important role in the process of loading sugars in the leaves. A symplastic mode of loading is indicated by high numbers of plasmodesmata. In some families, the sheath cells around the minor leaf veins are modified as phloem and xylem transfer cells. These cells are characterized by unlignified wall ingrowths. The leaves of some monocotyledons and dicotyledons possess enlarged vascular bundle sheath cells around the minor veins. The long-distance transport of water from roots to leaves occurs within the xylem in a series of highly specialized cells called tracheary elements.

Gene mutations provide the primary means of understanding gene structure and function in plants. A large number of mutants have been identified that affect a wide range of anatomical traits, ranging from embryogenesis to the adult plant. Numerous mutants have been isolated that directly control the root and shoot development, meristem behavior, epidermal cell formation, root hair and trichome development, and vascular tissue differentiation. Hybridization occurs when two different, naturally occurring plant populations show a breakdown in reproductive isolation and an exchange of genes between diverse individuals takes place. In several cases, the hybrids are more or less intermediate in quantitative features. The Aloineae are a well-defined tribe of the monocotyledonous family Liliaceae that provides an insight into the inheritance of leaf anatomical characters. Wood quality is determined by the combined effects of several interrelated and variable wood properties. Heritable wood properties include the amount of juvenile and mature wood, grain pattern, individual cell size and wall characteristics, and chemical properties of the cell wall. Some wood properties can be manipulated during processing, but others are stable features that can only be altered by a focused tree-breeding program.

Systematics is a broad field of inquiry that uses the characteristics and data from many disciplines for describing, naming, classifying, identifying, and determining relationships among plants. Anatomy broadens the base of systematic investigations by providing another set of characters that indicate relationships in harmony with external features. As with morphological characters, some anatomical features are useful in determining phylogenetic trends, whereas others delimit families, genera, or species. The secondary xylem has proved to be highly significant in elucidating higher-level plant phylogenies. One of the greatest achievements of plant anatomy has been the elucidation of the origin and subsequent trends of specialization of the angiosperm vessel element. The angiosperm vessel elements have been phylogenetically derived from scalariform-pitted tracheids by the progressive loss of pit membranes in the regions of tracheid overlap. The methodology of cladistic analysis has become the most widespread approach to modern phylogenetic reconstruction. A hypothesis of the relationship between two or more taxa is based on their shared possession of a derived character state. Anatomy provides important derived character states for the recognition of closely related taxa.

This chapter describes the various anatomical responses of higher plants to wounds or infections, and includes an analysis of how plants have evolved growth forms to cope with the changing stress patterns in natural environments. Multiple defenses occur in plants in response to stress and invasion of pathogens. Some of these defenses are structural and are often accompanied by chemical alterations in cells and tissues. Plant defenses can be pre-infectional or post-infectional responses. Defenses can be passive in the sense that they are preformed barriers to infection or active mechanisms of resistance that are formed in direct response to an injury or the activities of harmful invaders. The cuticle provides a very effective passive defense. The principal active anatomical response of plants to wounds and infections is to wall off the injured or diseased region. Lignification of cell walls and callose deposition are other common responses of plant tissues to injury. Several structural features that can potentially increase plant resistance include thickening and lignification of cell walls, and increasing the amount of sclerenchymatous tissue, in addition to foliar pubescence, surface waxes, and mineral accumulation. Laticifers can also serve a defensive function by clogging the mouthparts of insects attempting to feed on a latex-producing plant.

Many species of plants yield natural fibers that are interwoven to manufacture a variety of valuable products including fabrics, cordage, paper, and brushes. Plant fibers are also incorporated into various composite materials in which a matrix phase is reinforced with fibers. At maturity, fibers typically lose their protoplasts, and thus play no role in metabolism. Fibers lend strength and resilience to the materials made with them. Fibers positioned in the phloem or cortical regions of the stem and leaf fibers of monocotyledons include a number of commercially important cells that are very strong and flexible and which are used in the manufacture of various products. In response to being naturally or experimentally displaced from their normal growth orientation, the main axis or lateral branches of actively growing stems are stimulated to form wood with an eccentric growth pattern that is composed of cells having both an atypical structure and a chemical composition. This secondary xylem is known as reaction wood. The reaction wood of gymnosperms forms on the lower side of the woody cylinder and is known as compression wood. Tracheids of compression wood possess walls with visible discontinuities and abnormal microfibril angles.

Many plants produce secretions that serve as animal attractants or food rewards in the form of nectar, oils, and food bodies. Some chemicals provide plants with their only means of defense by discouraging the visitation of harmful insects and herbivores. Human beings use these products as condiments, medicines, fragrances, dyes, and ornaments. Secretory products are composed of a variety of organic molecules and are secreted by plants in specialized secretory structures and secretory cells. Different types of secretory structures often produce chemically identical products. Many plants possess elongated secretory canals, ducts, or cavities that become lined with specialized secreting epithelial cells. External secretory structures include glandular trichomes, colleters, glands, nectaries, and hydathodes. Glandular trichomes vary widely in structure but typically possess a basal cell, stalk, and unicellular or multicellular secretory head. At maturity, the head contains an enlarged subcuticular space that becomes filled with essential oil or resin as secretion proceeds. Stinging hairs represent another trichome type and produce skin-irritating substances. Internal secretory structures encompass oil cells, secretory cavities and canals, and laticifers.

One form of evidence of past human activity is the recovery of plant materials such as seeds, fruits, stems, and wood that have been routinely utilized as food, in construction, as clothing, in religious or other ceremonies, or as fuel. A careful study of the anatomical record of these materials can be used to help reconstruct an accurate picture of the life of prehistoric people, and to extend the knowledge of the undocumented climatic conditions under which they lived. Preserved wood and charcoal samples are especially valuable in dating historical buildings and archaeological sites and for interpreting past climates by studying the successive growth rings within a tree trunk. Tree-ring widths vary with climate. Abundant precipitation and soil moisture result in wide rings, whereas under drought conditions or less-than-average rainfall the rings are narrow or absent. Fire, pests, and disease also leave their marks within the ring sequence. The basis for all tree ring studies is the construction of a regional master chronology that extends back in time without interruption. The requirement of identifying and dating annual growth rings is achieved by utilizing a technique known as cross dating.

Forensic botany—the use of botanical evidence in courts of law—has proven to be useful in both civil and criminal cases. Evidence obtained from plants—including structural information—has gained wide acceptance as either direct or indirect evidence. The careful microanalysis of plant cells, tissues, or organ fragments at both the light-microscope and scanning-electron-microscope levels can provide compelling evidentiary arguments for resolving a variety of legal questions. Food plants also provide a source of forensic evidence. A record of what the victim ate just before death can be obtained by identifying the plant cells that are present in stomach contents. In some cases, the exact restaurant that served the last meal can also be located. The histological features of wood or wood fragments enable wood to be readily identified by family and genus. Obtaining diet and nutritional information on the domestic and wild herbivores represents a significant major application of plant anatomical research. Detailed food habit data and preferences are important because they relate to animal population size and fluctuation, range, and other complex interrelationships. Histological analysis of the herbivore diet has the advantage that materials can be microscopically examined at any stage of digestion, both recently consumed and as fine particles obtained from stomach contents and fecal droppings.

Wood technology deals with the physical appearance, anatomical structure, and mechanical and chemical properties of wood. All these features affect wood figure, strength, shrinkage patterns, and deformation. The physical properties of wood are derived from its particular molecular constitution, its cell wall organization, and the interaction of its structural units. External influence such as water content, shrinkage, and swelling, which may cause warping and checking, also affect the physical properties of wood. Weight is controlled by two major variables: the amount of solid cell wall material present and the quantity of water in the sample. Water is located in wood as bound water in the cell wall and as free water in the numerous spaces of the cell lumina and intercellular cavities. As the walls of individual cells lose water, they become thinner, and shrinkage of the wood occurs. Due to the stresses that are incurred in different directions by individual wood cells during the drying process and the complicated patterns of shrinkage that result, dried lumber tends to warp. The mechanical properties of wood are the multitude of measurable expressions that result from applied forces. These include strength properties, stiffness, elasticity, hardness, and toughness.

This chapter deals with details of the internal organization and the arrangement of cells and tissues within the three major organs of the primary plant body: the stem, the leaf, and the root. All stems are characterized by repetitive sequences of external nodes and internodes. The leaves and associated axillary buds are positioned at the nodal regions. Leaves are initiated as lateral protuberances on the domelike stem apex, and they occur in a precise arrangement—or phyllotaxis—on the stem. A mature leaf is composed of a leaf base, a stalk-like petiole, and an expanded, flattened blade called lamina. Some taxa have small, leaf-like structures called stipules, positioned between the petiole and the stem. The outermost layers on both surfaces of the blade constitute the upper and lower epidermis. The roots of a plant are collectively called the root system. Roots are composed of three primary tissue regions: the outermost epidermal layer, a wide middle region called the cortex, and an inner core or stele. The innermost layer of the cortex is the endodermis, and it is composed of cells with lignin-like wall material deposited in bands called the Casparian strip.

This chapter describes the origin and structure of the primary plant body. The postembryonic primary plant body arises from small, organized cell populations termed “meristems” that are located at the tips of the stems and the roots. Meristems are regions of active cell division, enlargement, and differentiation. The vegetative shoot apical meristem of angiosperms has a stratified organization, with two or more outer tunica layers in which cell divisions are primarily all anticlinal or oriented at right angles to the surface. Below the tunica layers is a region of corpus cells in which divisions occur in all planes. Active shoot apical meristems exhibit cytohistological zonation, in which the cells in the central zone are relatively large and divide infrequently as compared to the surrounding peripheral zone cells that divide more rapidly. A rib meristem underlies the central zone. Leaves are determinate organs initiated as groups of cells on the flanks of the shoot apex in precise and stable patterns. Leaf organogenesis commences with coordinated changes in the rate and pattern of cell division and expansion in different regions of the developing primordium.

Art objects, antiques, and musical instruments owe their unique qualities directly to their botanical origins. Therefore, it is possible to apply the special techniques of plant anatomy to help solve a number of fundamental questions relating to the history, preservation, and conservation of such materials. Plant anatomical evidence can be used to document attribution, date, and degree of deterioration, and to identify the materials used in object construction. Wooden objects often possess some cellular deterioration, and an anatomical examination at the light and electron-micrograph levels is essential to repair the damage. Deterioration occurs as a result of four general categories of decay processes: physical, chemical, mechanical, and biological. The recognition of decay provides valuable information that enables a museum curator to develop appropriate conservation and restoration procedures. Dendrochronological analysis is especially valuable for dating oil paintings on wooden panels, such as those produced on oak boards from the Middle Ages until the 17th century. Dendrochronological research has proven valuable in judging the authenticity of paintings given that a painting could not have been executed prior to the year of felling of the tree from which the panel board was constructed.

This chapter focuses on the origin and structure of the secondary plant body. All gymnosperms and most dicotyledons develop lateral meristems, which result in radial growth and are responsible for an increase in the width of the stems and the roots. Growth derived from the lateral meristems is called secondary growth and is composed of secondary tissues. Lateral meristems are termed “cambia” and function as biracial zones composed of initials and derivatives. The vascular cambium adds to the girth of the axis by the production of secondary xylem internally and secondary phloem externally. The outer protective layers of the axis are called periderm and are formed by the cork cambium, or phellogen. The vascular cambium develops a short distance behind the apical meristem. The cambium that forms within the vascular bundle is called fascicular cambium. The interfascicular cambium is initiated somewhat later from the renewed division of the parenchyma cells located between the original vascular bundles. A cambium in which the fusiform initials are overlapping and are of variable length is termed “unstratified.” A specialized stratified or stored cambium occurs when the fusiform initials are of nearly equal length, and are grouped in parallel and horizontal rows.

This contribution represents an extension of an earlier report covering the morphology and anatomy of the stem of flowering plants (Dickison 1992). As such, I have found it convenient to organize recent research under many of the same topic headings that were recognized previously. This chapter is different from my first contribution, in that selected literature devoted to root organization and structure is also summarized briefly. As before, this is not intended as an exhaustive literature review but a selection of current research that represents an overview on the progress made in the field of stem and root morphology and anatomy during the past few years. Also, as before, literature dealing with fossil plants, tissue culture, the phloem, the periderm, and regional, purely descriptive, or applied wood anatomy is not treated. The wide range of topics reviewed in this chapter, ranging from considerations of the cell theory, patterns of differentiation, evolution, and organismal morphology and computer modeling, reflect the current diversity of interests and research progress within the broadly based field of structural botany.

This report concerns itself with the morphology and anatomy of the stem of flowering plants. Research results dealing with both the primary body and secondary xylem are discussed. For the most part, literature dealing with fossil plants, tissue culture, the phloem, the periderm, and regional, purely descriptive, or applied wood anatomy is not treated. I have made no attempt to summarize systematic conclusions, some of which are reviewed in a previous volume (Kadereit 1989). With few exceptions, this discussion is restricted to literature published in the years 1986–1990. During this interval much new factual information has been obtained which has been responsible for the formation of new morphological concepts as well as the reinforcement, substantial modification, or even abandonment of existing theories on the nature, structure, origin, and evolution of angiosperm stems and tissues.

DICKISON, W. C. (Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 275993280) and A. L. WEITZMAN (Department of Botany, Smithsonian Institution, Washington, DC 20560). Floral morphology and anatomy of Bonnetiaceae. J. Torrey Bot. Soc. 125:268-286. 1998.-A detailed study of floral morphology and anatomy of three genera comprising a narrowly circumscribed dicotyledonous family Bonnetiaceae is presented. Flowers are subtended by bracteoles and possess a perianth that is clearly differentiated into a 5-parted calyx and corolla composed of rather thick members. The androecium contains numerous stamens that are united at the base to form a short tube or collar or the stamens are pentadelphous and grouped at the base into five bundles that are positioned in the petal planes. Stamen fascicle traces are reported for the first time in flowers of Bonnetiaceae and are shown to originate close to, or adnate to, the median petal trace. Occasionally, two fascicle bundles arise side by side from a common gap as double bundles. Anther morphology and attachment is variable. Ploiarium possesses nectariferous discs that alternate with the stamen clusters. The presence of nectariferous tissue in Archytaea is variable. Nectaries can be supplied by double bundles, supporting the view that the nectaries of Plioarium and Archytaea represent transformed stamens. Gynoecia are compound, superior, and 3-carpellate or 5-carpellate. Styles range from divided to the base to undivided, and uniformly have a papillate stigma and a central canal filled with transfusion tissue. Placentation changes from axile to essentially parietal at midlevel of the ovary. Ovules are bitegmic, and contrasted with the putatively closely related Theaceae in which the elongated inner integument forms the micropyle, the outer integument projects well beyond the inner one. In addition to the degree of style fusion and carpel number, other important differences among genera of Bonnetiaceae are found in anther wall structure and floral vascular patterns. Major features of variation in the floral vascular system relate to the number and degree of independence of sepallary and petal traces; degree of independence of the androecial vascularization; the organization of the central ovarian vascular system; and the condition of the stylar vasculature. Comparisons are made among the flowers of Bonnetiaceae, Theaceae and Cluisiaceae.

DIcIusON, W. C. (Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280). Morphology and anatomy of the flower and pollen of Saruma henryi Oliv., a phylogenetic relict of the Aristolochiaceae. Bull. Torrey Bot. Club 119: 392-400. 1992.-A study of the floral morphology and anatomy and pollen morphology of the monotypic Chinese genus Saruma was undertaken to provide a more thorough diagnosis of the plant and make comparisons with other members of the Aristolochiaceae. The possession of well-developed petals, a gynoecium of partially separate carpels, follicular fruit, and a monosulcate form of pollen document the primitive position of the genus. Pollen is semitectate and reticulate with a stratified, columellate wall structure. The gynoecium is of particular phylogenetic interest and is composed of a primitive form of three-trace carpel with an elongated, pubescent stigmatic region that extends along the exposed ventral (adaxial) surface. Numerous ovules are borne in two longitudinally oriented, submarginal rows and are vascularized by traces arising from the ventral bundles. The pattern of floral vascularization is similar to other members of the Aristolochiaceae, exhibiting the tendency for extensive fusion of vascular bundles. Unlike other Aristolochiaceae, oil cells and calcium oxalate crystals are absent from floral tissues. Saruma also diverges from the Aristolochiaceae by possessing stamens that become recurved inward at maturity, creating a functionally introrse dehiscence. Reproductive morphology provides compelling evidences for the segregation of Saruma to a distinct subfamily within the Aristolochiaceae. There is little convincing evidence to indicate that Saruma and Asarum share a common ancestry.

Further observations on the floral morphology and anatomy of the monotypic genusMedusagyne from the Seychelles are presented. The unique synovarious gynoecium is composed of numerous carpels that are attached to the side of a broad, elongated torus. The biovulate carpels are differentiated into a narrow ovary, a stout, erect, three-trace style, and a lobed, discoid stigma. The carpel wall is initially composed of thin-walled parenchyma, but at later stages of development the peripheral region becomes subdivided into many lignified sterile extensions. Carples show pronounced ontogenetic adaxial deformation, during which the upper ventral surfaces become expanded, greatly extending the ventral margins and forming a domelike cushion of carpel-derived tissue over the summit of the torus. The distal cushion remains separated from the flattened torus by a compressed cavity and eventually undergoes lignification, perhaps protecting the underlying gynoecium from chewing insects and exposure. Comparisons are made between the mature gynoecia ofMedusagyne and those of the genusDillenia. The occurrence of S-type sieve-element plastids inMedusagyne is reported for the first time, a feature in agreement with suggested thealean affinities of the family.

(...) Important and previously unreported differences between the two genera are: ovules bitegmic in Caryocar, ovules unitegmic in Anthodiscus; styles simple in Caryocar; styles compound in Anthodiscus; and major variation in floral vascularization including the more extensive fusion of major traces in Anthrodiscus. Stamen fascicle traces are reported for the first time in the family, and in combination with other features, clearly link the family to the Theales. (...)

The structure and development of roots and haustoria in 37 species of parasitic Scrophulariaceae was studied using light microscopy. The mature haustorium consists of two regions: the swollen “body” and the parent root, which resembles non-haustorial roots in structure. The body arises from the parent root and is composed of an epidermis, cortex, central region of xylem (the vascular core), a region of parenchyma (the central parenchymatous core), and the portion of the haustorium contained in the host tissue (the endophyte). The xylem of the vascular core is composed predominately of vessel elements. The central parenchymatous core is composed of parenchyma and col-lenchyma. Vessels extend from the vascular core through the central parenchymatous core to the endophyte. The endophyte is composed of parenchyma cells and vessel elements. No phloem is present in the body of the haustorium. Early stages in the development of the haustorium are exogenous. Initial periclinal divisions in the epidermis or outer cortex are followed by hypertrophy of cortical parenchyma. These events are followed by development of the vascular core from the pericycle, attachment of haustorium to the host by a specialized layer of cementing cells or root hairs, and penetration of the host by dissolution of host cells.

A comprehensive anatomical study of the nodes and leaves of 21 species in five genera of Staphyleaceae was conducted to clarify the systematics and major trends of specialization and radiation within the family. The fundamenta staphyleaceous nodal pattern is trilacunar, three-trace, although a considerable range of variation exists within genera in numbers of traces and gaps and in the nature and course of individual traces. The nodes of most species of Euscaphis, Staphylea, and Turpinia have a distinctive nodal anatomy characterized by small accessory or subsidiary traces. Features of the lamina that show variation and are useful in generic and subfamilial delimitation include: mature stomatal type, mucilaginous and papillate epidermal cells, presence or absence of a hypodermis, presence or absence and type of vein sheathing, occurrence of domatia, and trichome type. Presumably calcium oxalate crystals of the druse or prismatic type occur in all taxa. The two subfamilies of Staphyleaceae are well defined...

Vegetative and reproductive anatomy and morphology are described for the first time for Tetracarpaea tasmannica Hook., a small shrub endemic to Tasmania. Tetracarpaea, a monotypic genus, has many characteristics of other woody Saxifragaceae, such as wood with solitary pores, scalariform perforation plates, sparse axial xylem parenchyma, tracheids, spiral thickenings in tracheary elements, and perforated ray cells. The tracheary elements of Tetracarpaea are much smaller than those characteristic of the Escallonioideae, a feature probably related to its montane forest habitat. Other features of Tetracarpaea inconsistent with most Escallonioideae include dark-staining deposits in the ray cells; a unilacunar, one-trace nodal pattern; lack of unicellular foliar trichomes; simple craspedodromous venation; areole development that is lacking or incomplete; straight and tapered veinlets; abaxial fibers associated with the foliar vascular bundles; and lack of bundle sheaths. The genus is further characterized by complete, hypogynous, tetramerous flowers. The essentially apocarpous gynoecium has multiovulate carpels, each supplied by three veins that reach the stigma. Ovules are anatropous, bitegmic, and crassinucellate. Lateral sepal bundles are derived either from the sepal midrib or from the petalplane bundles; stamens are supplied by independent traces or by bundles originating from compound traces in both sepal- and petal-planes. The follicular fruits possess a sclerenchymatous endocarp and contain winged seeds that have a membranous testa, a ridged surface, and a cellular endosperm. Reproductive morphological and anatomical features are more consistent with features of the Saxifragoideae than with the Escallonioideae or the Cunoniaceae, although the essentially apocarpous gynoecium with multiovulate carpels is not found in these groups. Vegetative and reproductive characteristics indicate that Tetracarpaea is more closely related to Saxifragaceae than to Cunoniaceae. It is possible this isolated genus should have separate familial status.

Developmental study of the stem-node-leaf vascular continuum of Austrobaileya scandens White reveals that the vasculature within each leaf originates from a single procambial strand, that becomes separated into two strands only at the junction of leaf and stem. At lower levels in the stem the two strands become incorporated into independent portions of the stele. At later stages of development the solitary vascular bundle within the young leaf undergoes considerable lateral growth, resulting in an essentially continuous arc of vascular tissue. Ontogenetic evidence indicates that the vascular bundle in the midrib of the lamina should be regarded as a fundamentally single bundle and not interpreted as two bundles that have undergone various degrees of secondary fusion. A condition of two totally separate bundles extending the entire length of the leaf was not encountered. Our observations confirm the characterization of Austrobaileya as an example of "second rank" level of leaf vasculature. Nodal anatomy emphasizes the extremely isolated taxonomic position of Austrobaileya within the primitive dicotyledons. THE DISCOVERY ofthe nodal anatomical pattern in which a unilacunar node is associated with two leaf traces, each related to an independent portion of the stem vascular cylinder, brought about a reassessment of ideas relating to the evolution of nodal vasculature in dicotyledons. Suggestions were made that the unilacunar, twotrace nodal condition was primitive in dicotyledons (Canright, 1955; Marsden and Bailey, 1955; Bailey, 1956). This idea was subsequently accepted by a number of individuals (Eames, 1961; Cronquist, 1968; Foster and Gifford, 1974). One of the primary evidences used in support of the primitive nature of the 2:1 node is its occurrence (or modifications thereof) in various members of the primitive Ranalean complex, including the monotypic family Aus

Five genera and 12 species of Staphyleaceae were examined with respect to systematic floral morphology and anatomy. Detailed descriptions of floral structure and vascularization are provided. Features of systematic and evolutionary importance in the family include the number and type of fusion of floral parts, placentation type, occurrence of a vascularized disk, and the degree of independence of floral vascular traces. Flowers of Tapiscia sinensis lack a disk, and the bicarpellate gynoecium, containing no internal ovarian septation, culminates a trend toward carpel fusion and reduction in ovular number that has resulted in a unilocular structure with a solitary ovule attached to a more derived basal or subbasal placenta. The progressive fusion of floral parts in the Staphyleaceae has been accompanied by the characteristic union of the androecial vascular supply and sepal-plane bundles, which subsequently divide to form an externally situated stamen vasculature and internal sepal strands. Huertea and Tapi...

The first description of the wood of the monotypic Madagascan genus Diegodendron is provided. The xylem of D. humbertii is characterised by short , solitary vessel elements with alternate lateral wall pitting and simple perforation plates, imperforate tracheary elements of the libriform fibre type, nearly all biseriate, imperfectly storied, homogeneous rays composed of procumbent cells only, and diffuse and diffuse-in-aggregates axial parenchyma. The specialised wood anatomy of Diegodendron supports a close alliance with both Sphaerosepalaceae and Malvales.

The high order foliar vein sheathing of 40 species representing 6 genera of Cunoniaceae was examined. The type, orientation, distribution, and proportion of the sheathing elements around the veinlet, including the terminal cells, are variable and useful for generic circumscription and subdivision. Terminal cells are tracheoidal or sclereidal types. A general trend towards the formation of specialized sclerenchymatous terminal elements is supported.

Veinlet sheathing of twenty-six species ofPancheria is described and illustrated. Within the genus foliar vein sheathing varies from almost completely lacking to abundant, and individual sheath cells show much variation in cell wall composition and structure. The topographical distribution of sheath cells along the vein system, when coupled with the structure of individual sheathing elements, can be utilized to distinguish three anatomical groups of species. Although the evolutionary sequence and ecological significance of the diverse sheath types are at present unresolved, features of vein sheathing appear to be of systematic significance and may provide an additional basis for a better understanding of infraspecific relationships within this genus.

A study of leaf anatomy of 24 genera of Cunoniaceae was made. The prevailing petiole vasculature is a nearly complete, usually adaxially flattened, medullated cylinder with the flat dorsal segment separated from the ventral arc. Medullary and cortical vasculation in Codia, Cunonia, Geissois and Pancheria is correlated with an increase in leaf coriaceousness. Very few characters are uniformly found in leaves of all species; these are druse or prismatic crystals, bifacial mesophyll and unicellular and simple trichomes. In most species vein sheathing occurs. Characters of the lamina that show variation and are useful in generic delimitation are: trichome type, presence of a hypodermis, occurrence of mucilaginous cells, presence of specialized terminal veinlet cells, major and higher order venation patterns, vein sheathing type, and mature stomatal types. Stomata are of the anomocytic, paracytic or anisocytic types. Leaves of various cunoniaceous species of xerophytic environments exhibit a leathery texture, thicker cuticle, more intensive sclerification along the veins, a sclerified hypodermis, and an increase in the amount of vascular tissue per unit area. Leaf anatomy does not provide immediate clues toward elucidating the relationships of cunoniaceous genera.

A comprehensive study of nodal anatomy of the Cunoniaceae has revealed an unusually diverse assemblage of nodal types, including patterns with "split-lateral" traces previously undescribed for dicotyledons. On the basis of leaf arrangement and nodal vascularization, six distinct nodal conditions are recognized in the family. The trilacunar, three-trace pattern is the ancestral type from which the multilacunar condition evolved by amplification in the number of lateral traces. The "split-lateral" condition, distinguished by the fusion of lateral leaf traces of adjacent leaves, or the bifurcation of a single trace, and their association with a "common gap," probably evolved concomitant with the transition from opposite to whorled leaves. The characteristic interpetiolar stipules of the Cunoniaceae are vascularized by veins originating from lateral leaf traces, or by a combination of complete lateral traces and veins arising from lateral leaf traces. Both Aphanopetalum and Bauera possess unilacunar one-trace nodes. The most satisfactory family placement of both genera remains uncertain, although the unilacunar nodes of Bauera can reasonably be interpreted as a case of reduction from the trilacunar pattern in response to reduced plant size.

Summary Aspects of vegetative and floral anatomy of the monotypic genera Lachnanthes and Lophiola are described and compared. Lophiola and Lachnanthes are anatomically very distinct from one another and the taxonomic placement of both genera within the same tribe is not supported. The relationships of the genera to other taxa remain unclear.

Pollen of 23 species representing all five genera was examined by light microscopy, scanning electron microscopy, and a selected number in transmission electron microscopy. For the most part the family is palynologically rather uniform with the occurring variation forming a morphological continuum. Staphyleaceae pollen is tricolporate, tectate, circular to triangular in outline in polar view and usually spheroidal. Ectoapertures are long to very long, recessed, and granular. Endoapertures range from poorly developed in Huertea and Tapiscia to well defined in Euscaphis, Slaphylea, and Turpinia, and are either bounded by the colpi margins or transversely extended. Periapertural exine thinnings are present. The exine is stratified into tectum, columellae, foot layer and endexine. The endexine is either smooth, or as in Slaphylea, solid near the foot layer and granular on the inner surface. Tapiscia is characterized by the absence of endexine and an interrupted fool layer. The exine surface is tectat...

The anatomy and morphology of vegetative and reproductive structures of the monotypic, dicotyledonous genus Oncotheca were studied to evaluate the svstematic relationships of this New Caledonian endemic. Wood has remained at a low level of advancement, as evidenced by the solitary, angular pores and exclusively scalariform perforation plates. Imperforate tracheary elements are fiber tracheids, and asial parenchyma is diffuse to diffuse in aggregates in distribution. Sieve tube elements possess oblique to very oblique, compound sieve plates. Nodal anatomy is pentalacunar, and petioles contain a single, undissec.ted arc of vascular tissue. A number of apparently xeromorphic leaf features, including general foliar coriaceousness, may result from the poor availability of soil minerals. Leaves are characterized by a thick cuticle, uniseriate epidermis with nearly anomocytic stomata having paracytic or tetracytic tendencies and a bifacial mesophyll with two or three hypodermal layers. Foliar venation is brochidodromous. Highorder venation is characterized by freely ending branched veinlets and imperfect areolation. Flowers are relatively advanced, as evidenced by extensive fusion of parts and the tlnion of major floral bundles such as the ventral carpellary traces. A c]ose relationship between Oncotheca and the Aquifoliaceae and Ebenaceae is refuted. Support is given to the elevation of the genus to familial status and its placement near the Theaceae.