Axial Parenchyma Research Articles

Tehnološke lastnosti in uporabnost lesa velikega pajesena v primerjavi z lesom velikega jesena

Chinese sumac (Ailanthus altissima (Mill.) Swingle) is one of the most invasive alien species in Europe, and also in Slovenia. Due to its great renewal power the species is spreading rapidly, especially in abandoned agricultural and forest areas and along the traffic routes. It is botanically different from the European ash (Fraxinus excelsior L.), but it has similar tree habitus as well as similar structural characteristics of the wood. For this reason, we analysed the visual, anatomical and some physical and mechanical properties of both wood species. In all anatomical planes, the typical visual and colorimetric similarity of both studied woods was confirmed. Anatomically both ring porous wood species differ mainly in size and distribution of vessels, axial parenchyma and ray tissue. Wood of both species has a similar density as well, but the Chinese sumac has greater shrinkage. Some of the mechanical properties are comparable, although Chinese sumac wood has a lower modulus of elasticity and hardness and greater shear strength than ash wood. We can recommend that the wood of Chinese sumac can be used for production of pulp and paper, various panels and partly for less loaded constructions, which are not exposed to drastic climatic variability.

WOOD AND CHARCOAL ANATOMY OF FOUR MYRTACEAE SPECIES

ABSTRACT Qualitative and quantitative changes in anatomical characteristics of charcoal from Campomanesia xanthocarpa, Eugenia pyriformis, Myrcia retorta and Plinia peruviana were described to provide its correct discrimination and information’s to contribute to evaluations in illegal logging. The material came from Planalto Catarinense region, southern Brazil. For each species, three discs at diameter at breast height were collected from three randomly selected trees. All the disks were sectioned to obtain samples in different positions of the trunk (bark, intermediate and pith). Samples were wrapped in aluminum foil and carbonized in a muffle furnace, with a final temperature of 450 °C and a heating rate of 1.66 °C.min-1. In species analyzed, growth rings are few distinct, delimitated by fiber regions; solitary vessel and axial parenchyma diffuse or diffuse-in-aggregate is predominant. The wood to charcoal conversion caused variation in the following characteristics: vessel diameters decreased varying from 21.1% in Myrcia retorta to 33.4% in Eugenia pyriformis, while the vessel frequency increased with values from 50.7% to 92.3% related to the same species; height and width of the rays showed reduction, however, Myrcia retorta presented ruptures in ray cells and dimensions increased; ray frequency increased from 3.9% in Eugenia pyriformis to 54.1% in Campomanesia xantocharpa. Qualitative characteristics of wood from studied species remained in charcoal after carbonization at 450 oC, being possible to discriminate the material based on wood anatomy. In charcoal, vessels dimensions and frequency, after ray characteristics can be applied as first step in this Myrtaceae species distinction at forest control.

Comparative wood anatomy of some members of the genus <i>Caesalpinia</i> (Linn.) Sw

The wood anatomy of two varieties of Caesalpinia bonduc (L.) Roxb., that is the staminate and pistillate plants and four varieties of Caesalpinia pulcherrima (Linn).Sw, namely, Red, Yellow, Off-white and Pink petal plants were studied in search of wood anatomical characters that may be useful in the taxonomy of the Caesalpinia genus. Transverse, tangential longitudinal and radial longitudinal sections of the woods were made and some other parts of the woods were macerated. Qualitative and quantitative characters were observed and measured respectively, in all the taxa. The data were subjected to Duncan multiple range test (DMRT), principal components analysis (PCA) and single linkage cluster analysis (SLCA). The results revealed that growth ring is absent in all the taxa studied. They all have diffuse porous woods with heterogenous, uniseriate rays and solitary vessels. Pistillate plant of C. bonduc is the only taxa with multiple ray cells. Apotracheal axial parenchyma type was unique to the staminate plant of C. bonduc while paratracheal type was unique to C. bonduc pistillate. All the varieties of C. pulcherrima lack axial parenchyma. Tylose was absent in the pistillate plant of C. bonduc var. female and C. pulcherrima var. pink but present in all the other taxa. The first three components of the PCA accounted for 95.73% of the total variation among the taxa. It was concluded that quantitative and qualitative wood anatomical characters can be employed in differentiating the species and varieties of Caesalpinia studied.Keywords: Axial parenchyma, Caesalpinia, Fibres, Tylose, Vessels, Wood anatomy

Tree rings reveal the reduction of Cd, Cu, Ni and Pb pollution in the central region of São Paulo, Brazil

The concern about environmental pollution has risen in the last decades because of its effects on human's health. However, evaluation of the exposure to certain pollutants is currently hampered by the availability of past environmental data. Tree rings are an alternative to reconstruct environmental variability of pre-instrumental periods. Nevertheless, this approach has some reported limitations including migration of chemical elements in the tree rings. The aim of this study was to evaluate the distribution of Cd, Cu, Hg, Na, Ni, Pb, Zn in the tree rings of Tipuana tipu (Fabaceae) to aid the reconstruction of past environmental pollution. We sampled trees in the central region of the city of São Paulo, Brazil, and scanned their tree rings using LA-ICP-MS. We used these data to evaluate the temporal trends of chemical elements under investigation. Results show a non-random distribution of these chemical elements within the tree rings, with higher content in the cell-walls of vessels and lower content in the fibers. Sodium was the only element intimately related to the axial parenchyma cells. Due to differences in elemental composition of xylem cells, temporal trends where evaluated using distinct quartiles of data distribution in each tree ring. The first quartile represents the lower content found in fibers and parenchyma, while the third quartile corresponds to the higher content found in vessels. Data from vessels better represent the decreasing trend of Cd, Cu, Pb, and Ni in the last three decades. This reduction is less significant for Na and Zn. Our results highlight the potential to improve the records of environmental pollution using data from different cells. Pronounced reduction in Pb may be attributed to the lead phase-out in gasoline, while the decreasing trend of Cd, Cu, Ni pollution is probably related to increasing efficiency of vehicles and the deindustrialization of São Paulo.Chemical elements are non-randomly distributed in tree rings. Chemical content of vessels cell-walls is a reliable record of metal pollution, which is decreasing in São Paulo.

Cenozoic conifer wood from the Gore Lignite Measures, Southland, New Zealand

ABSTRACTWell preserved fossil wood in the form of tree stumps, logs, branches, roots and occasionally bark is common throughout the Gore Lignite Measures, southern New Zealand. The main objective of the present study is to identify the range of forest trees present using anatomical features such as: distinct growth rings; presence or absence of axial parenchyma; uniseriate to triseriate, opposite to alternate, separate or contiguous tracheid pitting; and taxodioid, cupressoid and araucarioid cross-field pitting. Specimens of silicified and lignified wood are described and illustrated from four localities within the Late Oligocene–Early Miocene Gore Lignite Measures, Southland: Newvale Coal Mine; Mataura Coal Mine; Cosy Dell Coal Pit; and Bennett’s Pit. The fossil wood specimens include examples of Araucariaceae, Cupressaceae and Podocarpaceae. Three specimens from Newvale Mine resemble Araucariaceae, while one is assigned to Cupressaceae. Cosy Dell Coal Pit preserved branches of Podocarpaceae. Large stumps and branches preserved at the Mataura Coal Mine are identified as Cupressaceae and Podocarpaceae. Wood recovered from Bennett’s Pit resembles either Cupressaceae or Podocarpaceae. Araucariaceae, in the form of Agathis Salisb. trees are today restricted to the northern North Island. Cupressaceae and Podocarpaceae are still extant in modern forests throughout New Zealand. So far, no angiosperm wood has been recognised from the lignite deposits. The forests in which these trees lived were in or near oligotrophic swamps on a deltaic plain. Identification of samples of fossil wood provides new data that can be used to reconstruct the forest vegetation of the Gore Lignite Measures.

Geometric analysis of intrusive growth of wood fibres in Robinia pseudoacacia

ABSTRACT All cell types of the secondary xylem arise from the meristematic cells (initials) of the vascular cambium and grow under mechanical constraints emerging from the circular-symmetrical geometry that characterises many tree trunks. The course of intrusive growth of cambial initials has been elucidated, but is yet to be described in the case of xylem fibres. This study explains the geometry of intrusive growth of the secondary xylem fibres in the trunk of Robinia pseudoacacia. Long series of serial semi-thin sections of the vascular cambium and the differentiating secondary xylem were analysed. Since fibres grow in close vicinity to expanding cells of the derivatives of the vascular cambium, we assumed that they have similar growth conditions. Dealing with the cylindrical tissue of the vascular cambium in a previous study, we used a circularly symmetrical equation for describing the growth mechanism of cambial initials. Like the cambial initials, some of the cambial derivatives differentiating into the various cell types composing the secondary xylem also exhibit intrusive growth between the tangential walls of adjacent cells. As seen in cross sections of the cambium, intrusively growing initials form slanted walls by a gradual transformation of tangential (periclinal) walls into radial (anticlinal) walls. Similarly, the intrusive growth of xylem fibres manifests initially as slants, which are formed due to axial growth of the growing cell tips along the tangential walls of adjacent cells. During this process, the tangential walls of adjacent cells are partly separated and dislocated from the tangential plane. The final shape of xylem fibres, or that of vessel elements and axial parenchyma cells, depends upon the ratio of their intrusive versus symplastic growths in the axial, circumferential and radial directions.

Living Cells in Wood 3. Overview; Functional Anatomy of the Parenchyma Network

The very different evolutionary pathways of conifers and angiosperms are very informative precisely because their wood anatomy is so different. New information from anatomy, comparative wood physiology, and comparative ultrastructure can be combined to provide evidence for the role of axial and ray parenchyma in the two groups. Gnetales, which are essentially conifers with vessels, have evolved parallel to angiosperms and show us the value of multiseriate rays and axial parenchyma in a vessel-bearing wood. Gnetales also force us to re-examine optimum anatomical solutions to conduction in vesselless gymnosperms. Axial parenchyma in vessel-bearing woods has diversified to take prominent roles in storage of water and carbohydrates as well as maintenance of conduction in vessels. Axial parenchyma, along with other modifications, has superseded scalariform perforation plates as a safety mechanism and permitted angiosperms to succeed in more seasonal habitats. This diversification has required connection to rays, which have concomitantly become larger and more diverse, acting as pathways for photosynthate passage and storage. Modes of growth such as rapid flushing, vernal leafing-out, drought deciduousness and support of large leaf surfaces become possible, advantaging angiosperms over conifers in various ways. Prominent tracheid-ray pitting (conifers) and axial parenchyma/ray pitting to vessels (angiosperms) are evidence of release of photosynthates into conductive cells; in angiosperms, this system has permitted vessels to survive hydrologic stresses and function in more seasonal habitats. Flow in ray and axial parenchyma cells, suggested by greater length/width ratios of component cells, is confirmed by pitting on end walls of elongate cells: pits are greater in area, more densely placed, and are often bordered. Bordered pit areas and densities on living cells, like those on tracheids and vessels, represent maximal contact areas between cells while minimizing loss of wall strength. Storage cells in rays can be distinguished from flow cells by size and shape, by fewer and smaller pits and by contents. By lacking secondary walls, the entire surfaces of phloem ray and axial phloem parenchyma become conducting areas across which sugars can be translocated. The intercontinuous network of axial parenchyma and ray parenchyma in woods is confirmed; there are no “isolated” living cells in wood when three-dimensional studies are made. Water storage in living cells is reported anatomically and also in the form of percentile quantitative data which reveal degrees and kinds of succulence in angiosperm woods, and norms for “typically woody” species. The diversity in angiosperm axial and ray parenchyma is presented as a series of probable optimal solutions to diverse types of ecology, growth form, and physiology. The numerous homoplasies in these anatomical modes are seen as the informative results of natural experiments and should be considered as evidence along with experimental evidence. Elliptical shape of rays seems governed by mechanical considerations; unusually long (vertically) rays represent a tradeoff in favor of flexibility versus strength. Protracted juvenilism (paedomorphosis) features redirection of flow from horizontal to vertical by means of rays composed predominantly or wholly of upright cells, and the reasons for this anatomical strategy are sought. Protracted juvenilism, still little appreciated, occurs in a sizeable proportion of the world’s plants and is a major source of angiosperm diversification.

Radial variation of wood properties in Neolamarckia cadamba trees from an East Java community forest

Radial variations in wood properties, cell morphologies and cell proportions were investigated for nine 4-year-old Neolamarckia cadamba trees planted in a community forest in East Java, Indonesia. The relationships between stem diameter and wood properties, cell morphologies or cell proportions were determined to ascertain the effects of stem diameter on these properties. In the radial variations, almost all of the wood properties, cell morphol- ogies and cell proportion in N. cadamba were changed at around 4 to 6 cm distance from the pith, except for fibre diameter, and the proportion of fibre and axial parenchyma. For trees with larger stem diameter, the vessel diameter was also found to increase. In addition, the ray parenchyma and cell wall proportions in trees with larger stem diameter were lower than those in trees with smaller stem diameter. However, the wood properties obtained from the larger stem diameter trees did not always show lower values. The wood properties in N. cadamba were correlated to fibre wall thickness and vessel diameter.

Morphological imaging and quantification of axial xylem tissue in Fraxinus excelsior L. through X-ray micro-computed tomography

The popularity of X-ray based imaging methods has continued to increase in research domains. In wood research, X-ray micro-computed tomography (XμCT) is useful for structural studies examining the three-dimensional and complex xylem tissue of trees qualitatively and quantitatively. In this study, XμCT made it possible to visualize and quantify the spatial xylem organization of the angiosperm species Fraxinus excelsior L. on the microscopic level. Through image analysis, it was possible to determine morphological characteristics of the cellular axial tissue (vessel elements, fibers, and axial parenchyma cells) three-dimensionally. X-ray imaging at high resolutions provides very distinct visual insight into the xylem structure. Numerical analyses performed through semi-automatic procedures made it possible to quickly quantify cell characteristics (length, diameter, and volume of cells). Use of various spatial resolutions (0.87–5 μm) revealed boundaries users should be aware of. Nevertheless, our findings, both qualitative and quantitative, demonstrate XμCT to be a valuable tool for studying the spatial cell morphology of F. excelsior.

Lagerstroemia L. fossil wood from the Indus molasse sediments (possibly late Miocene) of Trans-Himalayan region and its phytogeographic and climatic significance

The collision of the Indian and Eurasian plates led to the formation of Himalaya. The uplift of Himalaya had a direct impact on the intensification of South Asian monsoon which has influenced the evolution of many Asian biotas. The plant fossil records from the Indus-Tsangpo-Yarlung Suture Zone are exceptionally significant for the reconstruction of palaeoclimate during the collision and uplift of the Himalaya. However, these records from the Himalayan region are poorly known. Here we report a fossil wood from the Trans-Himalayan region unearthed from the possibly late Miocene Indus molasse sedimentary succession (Karit Formation) of the Kargil district, Jammu and Kashmir. The anatomical features of the fossil wood such as semi-ring porosity, simple perforation plates, vestured intervessel pits, vasicentric to confluent axial parenchyma, exclusively uniseriate, homocellular rays, septate fibres and crystalliferous parenchyma strands suggest its close affinity with Lagerstroemia L. and particularly with Lagerstroemia parviflora Roxb. of the family Lythraceae. The climatic tolerance and anatomical details of the nearest living relative of the fossil indicate that during the late Miocene the climate of the Trans-Himalayan region was warmer and the area was lower in comparison to the modern day elevation of ~3559 m.

Systematic and phylogenetic implications of the wood anatomy of six Neotropical genera of Primulaceae

Our main goals were to identify diagnostic characters at the species, genus, and subfamily levels, find anatomical features with potential for future morphological and molecular (combined) phylogenetic analyses, and to reconstruct the evolution of wood anatomical characters in two subfamilies of Primulaceae in a molecular phylogenetic framework. We investigated twenty-seven species from the woody Myrsinoideae (4 genera) and Theophrastoideae (2 genera) using scanning electron, light, and epifluorescence microscopy. Samples were prepared using standard protocols. Based on the wood anatomical characters, we were able to identify synapomorphies and to detect evolutionary trends of interest for the genera and subfamilies. Both subfamilies share the presence of diffuse porosity, simple perforation plates, septate fibres, and scanty paratracheal axial parenchyma. Theophrastoideae species have rays > 10 cells wide and short (< 350 µm) vessel elements, and Myrsinoideae have breakdown areas in rays and longer vessel elements. Ardisia and Stylogyne have scalariform intervessel pits, Myrsine exhibit breakdown areas in rays, and two Cybianthus species from subgenus Weilgetia have distinguishing features (e.g., scalariform perforation plate in C. nemoralis and the absence of rays in C. densiflorus). Overall, when combining characters, we were able to segregate the Neotropical Primulaceae subfamilies and genera from each other and from the subfamily Maesoideae based on wood anatomy.

Comparative Wood Anatomy and Chemical Composition of Millettia mossambicensis and Millettia stuhlmannii from Mozambique

The wood anatomy and chemistry of a relatively lesser used wood species, known in Mozambique as nsangala (Millettia mossambicensis J. B. Gillett), was compared to overexploited species jambire (Milletia stuhlmannii Taub.) to provide diagnostic features for safe discrimination. The anatomical results showed that both species shared several similarities such as intervessel pitting size range (8 µm to 11 µm), rays composed of only procumbent cells, fiber dimensions (average length up to 1359 µm and wall thickness up to 10 µm), and banded axial parenchyma. The extractives and lignin content were higher in jambire, while the carbohydrates and acetyl contents were higher in nsangala. The main anatomical feature separating the two species was the porosity pattern with semi-ring porous wood of nsangala compared to the diffuse-porous structure of jambire. Jambire had wider vessel lumina (200 µm) and up to 3 vessels/mm2 compared to nsangala vessel lumina of 86 µm and a frequency of 37 vessels/mm2.

The Role of Extractives and Wood Anatomy in the Wettability and Free Surface Energy of Hardwoods

The main goal of this paper was to clarify to what extent extractives and wood structure determine the surface properties of hardwoods, mainly tropical. The role of wood extractives relative to properties, such as wettability and free surface energy, has been confirmed. The most significant seemed to be cyclohexane extractives. It was further found that in the case of tested tropical wood species, the extractives contents were high. Moreover the important role of axial parenchyma in wood wettability was established. It was established that multiple regression analysis could be useful in understanding wood properties as the result of the complex structure of wood. The obtained data is crucial from a practical point of view for its disclosure of those wood species that require surface modification prior to varnish coating.

Wood and bark anatomy of Andriana (Heteromorpheae, Apiaceae) with phylogenetic implications

The wood structure was examined in two species of Andriana, and the bark structure in one species of this genus. The Malagasy endemic genus Andriana is similar to the southern African genera of the tribe Heteromorpheae (Apioideae, Apiaceae) in having axial secretory canals arranged in a single ring in the innermost part of the cortical parenchyma and radial dilatation of secondary phloem. This genus is distinctive, however, from the latter by the common presence of column-shaped to bottle-shaped epidermal cells with very thick cuticle. Helical thickenings on vessel walls have not been found in Andriana; thus this feature can be considered a synapomorphic trait only for the Heteromorpha clade rather than for the tribe Heteromorpheae, as it was previously suggested. Surprisingly, secretory canals in the secondary phloem of Andriana species lack sheaths of specialized axial parenchyma. The absence of these sheaths is thought to be unique within the suborder Apiineae, which comprises the families Araliaceae, Myodocarpaceae, Pittosporaceae, and Apiaceae.

Ontogeny, structure and occurrence of interxylary cambia in Malpighiaceae

Deviations in the regular pattern of secondary growth have occurred multiple times over the history of woody plants and these have been treated under the term cambial variant. Here we present a type of cambial variant that has been studied in the 19th century, but that has never been named or had its ontogeny studied in detail. This cambial variant generates a vascular cylinder with a conspicuous crenate pattern and it is found in two lianescent lineages of Malpighiaceae; Stigmaphyllon and a clade informally called the Banisteriopsis nummifera group. Twenty species of Stigmaphyllon and two species of the Banisteriopsis nummifera group were sampled from naturally growing population to investigate ontogenic history starting from shoot apex to the thickest portion of stem by using traditional anatomical methods All species in these two clades have a regular cambium that produces bands of non-lignified axial parenchyma in the xylem by the onset of secondary growth. These xylem parenchyma cells, after a period of secondary growth, acquire meristematic activity and give rise to new, variant cambia referred here as ‘interxylary cambia’. These new cambia give rise to new vascular tissues within the secondary xylem. In Stigmaphyllon the variant cambia give rise to a large quantity of variant phloem, and not much variant xylem, while in the members of the Banisteriospsis nummifera group a large quantity of both secondary xylem and phloem is formed by every new interxylary cambia. Xylem and phloem originated from both cambial types have features similar to those of other Malpighiaceae lianas, except for the absence of septate fibers and perforated ray cells, the presence of stratified phloem and prismatic crystals in the phloem of the Banisteriopsis nummifera group and a concentric ring of cortical secretory cells characteristic of Stigmaphyllon. The cambial variant interxylary cambia is here named for the first time, and this new term is proposed to unmistakably denote its origin from within the secondary xylem, which is likely a synapomorphy for these two Malpighiaceae lineages.

A contribution to the identification of charcoal origin in Brazil III: microscopic identification of 10 Cerrado species

Brazil has one of the richest biodiversities in the world. The Brazilian savanna is a hotspot for conservation priorities and its deforestation is of global concern. Conservation in this biome is threatened by unsustainable use of forests, such as illegal logging for charcoal production. Thus, government agents need to verify whether charcoal loads follow the Document of Forestry Origin (DOF). To improve charcoal identification, our study presents the microscopic description of 10 Cerrado species and provides an identification key to aid government agents during surveillance. We analysed charcoal samples with a scanning electron microscope. The method of carbonisation simulated real conditions. We chose species with similar wood anatomy (sparse axial parenchyma and narrow rays), which increases misidentification by forest controllers because of their difficulty to identify these features. Also, paratracheal scanty, diffuse and diffuse-in-aggregates parenchyma were harder to recognise in charcoal than in wood. Other features, such as vessels, rays and abundant axial parenchyma, were easily identified. The present work can be used as a part of a charcoal anatomy database focussed on preventing deforestation in Brazil and in other countries with similar problems.

Wood anatomy of five species from Mozambique and its potential application

SUMMARY: Wood trade is strongly dependent on global economic conditions. In Africa, the market for tropical wood also has dynamic changes. In Mozambique, the international demand for wood comes mainly from emerging economies such as China and India. Almost 70 % of the country is still covered by forests and other woody vegetation. There are many species with favorable properties for wood commerce, although, at present, this is restricted to a few species. We analyzed the wood anatomy of Acacia nigrescens, Combretum imberbe, Icuria dunensis, Pericopsis angolensis and Sterculia appendiculata and comment about properties and potential use based on their anatomical composition. In general, the species presented wood diffuse pores, simple perforation plates, alternate intervessel pits, deposits in vessels; abundant axial parenchyma; multiseriate rays, very thick-walled fibers and mineral inclusions. Based on anatomical characteristics, the studied species have great potential for use in panels industry, furniture, floor, structures and craftwork.

Automated identification of Lauraceae by scale-invariant feature transform

An image dataset of the cross-sectional optical micrographs of the Lauraceae species including 39 species in 11 genera, capturing at least one full annual ring, was investigated by scale-invariant feature transform (SIFT), a computer vision-based feature extraction algorithm. We found an image of 900 × 900-pixel size at a pixel resolution of ca. 3 µm, corresponding to the actual size of 2.65 × 2.65 mm2, as the minimum requirement for the image dataset in terms of the accuracy of the recognition at both the genus and species levels. Among the several classifiers investigated, the linear discriminant analysis (LDA) presented the best performance reaching a maximum of 89.4% in the genus with a species identification of approximately 96.3%. Cluster analysis of all the SIFT descriptors for each image yielded practical information regarding the descriptors; they recognize selectively the cell lumina, cell corners, vessels, and axial and ray parenchyma cells. Therefore, the difference between the genus or species levels was determined per the variation in the quantities of these computer-based properties. Another clustering approach, the hierarchal dendrogram, was applied to visualize the numerical distances between the genus and species. Interestingly, even Machilus and Phoebe, which are difficult to distinguish by conventional visual inspection, are quite distantly classified at the genus level. In contrast, some species in Cinnamomum, Machilus and Litsea were categorized into different subgroups rather than the original genus. Microscopic wood identification is found to be possible at the genus level; however, the numerical dataset of the morphological features has various overlapping clusters, causing the genus-level identification of the Lauraceae to be more difficult than species-level identification.

The first Glyptostroboxylon from the Miocene of Turkey

ABSTRACTSilicified wood preserved in the Güdül fossil forest site in the Galatian Volcanic Province (GVP) near Ankara in Central Anatolia is described. The material comprises six petrified wood samples that date from early to middle Miocene. The woods have very low rays (2–5 cells high), bordered tracheidal pitting (9–10 μm), pinoid cross-field pits and very thin, unpitted, smooth walls of axial parenchyma and rays. This combination of characters indicates affinity to the fossil-genus Glyptostroboxylon. The presence of this wood genus suggests that the local environment was either riparian or wetland forest.

Panascleroticoxylon crystallosa gen. et sp. nov.: a new Miocene malpighialean tree from Panama

ABSTRACTWe report fossil wood specimens from two Miocene sites in Panama, Central America: Hodges Hill (Cucaracha Formation; Burdigalian, c. 19 Ma) and Lago Alajuela (Alajuela Formation; Tortonian, c. 10 Ma), where material is preserved as calcic and silicic permineralizations, respectively. The fossils show an unusual combination of features: diffuse porous vessel arrangement, simple perforation plates, alternate intervessel pitting, vessel–ray parenchyma pits either with much reduced borders or similar to the intervessel pits, abundant sclerotic tyloses, rays markedly heterocellular with long uniseriate tails, and rare to absent axial parenchyma. This combination of features allows assignment of the fossils to Malpighiales, and we note similarities with four predominantly tropical families: Salicaceae, Achariaceae, and especially, Phyllanthaceae, and Euphorbiaceae. These findings improve our knowledge of Miocene neotropical diversity and highlight the importance of Malpighiales in the forests of Panama prior to the collision of the Americas.