Reconstruction of an enigmatic Pennsylvanian cone reveals a relationship to Sphenophyllales.

PREMISE: We studied the 3D morphology of a small, well-preserved cone from the Pennsylvanian Mazon Creek Lagerstätte to characterize its structure and determine its systematic affinity. Previously tentatively assigned to the enigmatic Tetraphyllostrobus, we show that it differs in key respects from that genus as described. METHODS: We systematically compared the new fossil with relevant Paleozoic cone genera and employed advanced imaging techniques, including scanning electron microscopy, Airyscan confocal super-resolution microscopy, optical microscopy, and X-ray microcomputed tomography to visualize and reconstruct the fossil cone in 3D. RESULTS: The analyses demonstrate unequivocally that the sporophylls of the new Mazon Creek cone are arranged in whorls of six and have characters typical of Sphenophyllales, including epidermal cells with undulatory margins and in situ spores assignable to Columinisporites. The combination of characters, including sporophyll arrangement, anatomy, and spore type, supports the establishment of Hexaphyllostrobus kostorhysii gen. et sp. nov. within Sphenophyllales. Furthermore, we show that Tetraphyllostrobus, although originally described as possessing smooth monolete spores, actually possesses Columinisporites-type spores, indicating that it, too, was most likely a sphenophyll. CONCLUSIONS: The recognition of Hexaphyllostrobus contributes to our knowledge of Pennsylvanian sphenophyll diversity, and in particular increases the number of species with in situ Columinisporites-type spores. Attribution of Hexaphyllostrobus to Sphenophyllales calls into question current interpretations of Tetraphyllostrobus suggesting that future research on better-preserved macrofossil material may demonstrate a sphenophyllalean relationship.

Assessing the effects of water quality on leaf morphoanatomy, ultrastructure and photosynthetic pigment content of Salvinia auriculata Aubl. (Salviniaceae).

The objective of this study is to evaluate the effects of physical-chemical and biological variables of the water of the Capibaribe River (state of Pernambuco, Brazil) on leaf anatomy, including ultrastructure and photosynthetic pigment of Salvinia auriculata. Specimens of S. auriculata collected in the Gurjaú River, an area with a low pollution degree, were acclimatized in Hoagland's solution and then subjected to three water samples of the Capibaribe River with different levels of pollution. Twenty-one physical-chemical and biological variables were analyzed according to the Standard Methods for the Examination of Water and Wastewater. The results showed that the samples of the Capibaribe River presented nine parameters that did not comply with the current Brazilian legislation. After 15 days of bioassay, S. auriculata presented variations in mesophyll and cuticle thickness, changes in trichome morphology and accumulation of phenolic compounds. No significant differences were observed for photosynthetic pigment content and leaf length of S. auriculata. Multivariate analyses (PCA and Cluster) showed that the point in the Capibaribe River with the highest number of variables that do not comply with the current legislation was responsible for major structural and chemical changes observed in S. auriculata.

A revised classification of Chinese Davalliaceae based on new evidence from molecular phylogenetics and morphological characteristics.

Although the phylogenetic framework of Davalliaceae is known, the classification of Chinese Davalliaceae is still controversial. In this study, a molecular phylogenetic tree of 60 accessions, including 29 species produced in China, was constructed using five plastid DNA markers-atpB, atpB-rbcL, rbcL, rbcL-accD, and accD. New data on studied specimens, field investigations, and scanning electron microscopy analysis of leaf epidermis and spores were used to reclassify Chinese Davalliaceae. The taxonomic position of Davallia canariensis was confirmed based on new evidence and a new key to sections of Chinese Davalliaceae was proposed. The taxonomically controversial genus Paradavallodes was confirmed as a polyphyletic group, and it was assigned to Davallia sect. Trogostolon and Davallia sect. Davallodes. Further, species endemic to China were delimited, 21 species were admitted to six sections of Davallia, two new combinations were proposed, two new synonyms were defined and a new key to Chinese species of Davalliaceae was presented.

Agathis trees of Patagonia's Cretaceous-Paleogene death landscapes and their evolutionary significance.

PREMISE OF THE STUDY: The fossil record of Agathis historically has been restricted to Australasia. Recently described fossils from the Eocene of Patagonian Argentina showed a broader distribution than found previously, which is reinforced here with a new early Paleocene Agathis species from Patagonia. No previous phylogenetic analyses have included fossil Agathis species. METHODS: We describe macrofossils from Patagonia of Agathis vegetative and reproductive organs from the early Danian, as well as leaves with Agathis affinities from the latest Maastrichtian. A total evidence phylogenetic analysis is performed, including the new Danian species together with other fossil species having agathioid affinities. KEY RESULTS: Early Danian Agathis immortalis sp. nov. is the oldest definite occurrence of Agathis and one of the most complete Agathis species in the fossil record. Leafy twigs, leaves, pollen cones, pollen, ovuliferous complexes, and seeds show features that are extremely similar to the living genus. Dilwynites pollen grains, associated today with both Wollemia and Agathis and known since the Turonian, were found in situ within the pollen cones. CONCLUSIONS: Agathis was present in Patagonia ca. 2 million years after the K-Pg boundary, and the putative latest Cretaceous fossils suggest that the genus survived the K-Pg extinction. Agathis immortalis sp nov. is recovered in a stem position for the genus, while A. zamunerae (Eocene, Patagonia) is recovered as part of the crown. A Mesozoic divergence for the Araucariaceae crown group, previously challenged by molecular divergence estimates, is supported by the combined phylogenetic analyses including the fossil taxa.

Foliar epidermal micromorphology and its taxonomic implications in some selected species of Athyriaceae.

For the robust identification of taxonomically complex fern family like Athyriaceae, light and scanning electron microscopy is significance implications. This article present first microscopic investigation of foliar micromorphology of 3 genera and 10 species belonging to Athyriaceae namely, Athyrium, Deparia, and Diplazium were collected from different localities in Malakand Division, Northern Pakistan. In present study we compare foliar micromorphology of all 10 species using standard protocols of light microcopy (LM) and scanning electron microscopy. Qualitative micromorphological variations in shape of epidermal cells, anticlinal wall pattern, stomatal type and shape, stomatal pore shape, guard cells shape, and trichomes types were studied. In addition, some quantitative characters were also studied and data were statistically analyzed in epidermal cell size, stomatal size, stomatal pore size, stomatal density, and stomatal index. The pivotal result of study include; shape of epidermal cell in all species is irregular on both abaxial and adaxial surfaces. The anticlinal walls are sinuous in most of the species but some species have irregular lobed and broadly lobed wall. Leaves are hypostomatic in all studied species. Two main categories of stomatal type were found: polocytic and anomocytic. Unicellular nonglandular trichomes were observed in only one species Athyrium mackinnoni. The variation in foliar micromorphological characters between the genera and within the species was useful in identification and classification and have potential taxonomic significance for species differentiation. An identification key using micromorphological characters are provided to distinguish genera and species.

Hornwort stomata do not respond actively to exogenous and environmental cues.

Backgrounds and Aims: Because stomata in bryophytes occur on sporangia, they are subject to different developmental and evolutionary constraints from those on leaves of tracheophytes. No conclusive experimental evidence exists on the responses of hornwort stomata to exogenous stimulation. Methods: Responses of hornwort stomata to abscisic acid (ABA), desiccation, darkness and plasmolysis were compared with those in tracheophyte leaves. Potassium ion concentrations in the guard cells and adjacent cells were analysed by X-ray microanalysis, and the ontogeny of the sporophytic intercellular spaces was compared with those of tracheophytes by cryo-scanning electron microscopy. Key Results: The apertures in hornwort stomata open early in development and thereafter remain open. In hornworts, the experimental treatments, based on measurements of >9000 stomata, produced only a slight reduction in aperture dimensions after desiccation and plasmolysis, and no changes following ABA treatments and darkness. In tracheophytes, all these treatments resulted in complete stomatal closure. Potassium concentrations are similar in hornwort guard cells and epidermal cells under all treatments at all times. The small changes in hornwort stomatal dimensions in response to desiccation and plasmolysis are probably mechanical and/or stress responses of all the epidermal and spongy chlorophyllose cells, affecting the guard cells. In contrast to their nascent gas-filled counterparts across tracheophytes, sporophytic intercellular spaces in hornworts are initially liquid filled. Conclusions: Our experiments demonstrate a lack of physiological regulation of opening and closing of stomata in hornworts compared with tracheophytes, and support accumulating developmental and structural evidence that stomata in hornworts are primarily involved in sporophyte desiccation and spore discharge rather than the regulation of photosynthesis-related gaseous exchange. Our results run counter to the notion of the early acquisition of active control of stomatal movements in bryophytes as proposed from previous experiments on mosses.

New data on the stem and leaf anatomy of two conifers from the Lower Cretaceous of the Araripe Basin, northeastern Brazil, and their taxonomic and paleoecological implications.

Pseudofrenelopsis and Brachyphyllum are two conifers that were part of the Lower Cretaceous (Aptian) taphoflora of the Crato Formation, Araripe Basin, northeastern Brazil. The former genus includes, so far, P. capillata and indeterminate species, whilst the latter is mainly represented by B. obesum, the most common plant megafossil recovered from that stratigraphic unit. Here, the stem and leaf anatomy of Pseudofrenelopsis sp. and B. obesum specimens is revisited, including the first report of some epidermal and vascular traits for both taxa from the Crato Formation. Along with its paleoecological significance, the new data suggest the presence of more than one Pseudofrenelopsis species in the Aptian taphoflora of the Araripe Basin and further support the taxonomic placement of B. obesum within Araucariaceae.

Proteomic analysis of stipe explants reveals differentially expressed proteins involved in early direct somatic embryogenesis of the tree fern Cyathea delgadii Sternb.

Using cyto-morphological analysis of somatic embryogenesis (SE) in the tree fern Cyathea delgadii as a guide, we performed a comparative proteomic analysis in stipe explants undergoing direct SE. Plant material was cultured on hormone-free medium supplemented with 2% sucrose. Phenol extracted proteins were separated using two-dimensional gel electrophoresis (2-DE) and mass spectrometry was performed for protein identification. A total number of 114 differentially regulated proteins was identified during early SE, i.e. when the first cell divisions started and several-cell pro-embryos were formed. Proteins were assigned to seven functional categories: carbohydrate metabolism, protein metabolism, cell organization, defense and stress responses, amino acid metabolism, purine metabolism, and fatty acid metabolism. Carbohydrate and protein metabolism were found to be the most sensitive SE functions with the greatest number of alterations in the intensity of spots in gel. Differences, especially in non-enzymatic and structural protein abundance, are indicative for cell organization, including cytoskeleton rearrangement and changes in cell wall components. The highest induced changes concern those enzymes related to fatty acid metabolism. Global analysis of the proteome reveals several proteins that can represent markers for the first 16days of SE induction and expression in fern. The findings of this research improve the understanding of molecular processes involved in direct SE in C. delgadii.

100-million-year-old conifer tissues from the mid-Cretaceous amber of Charente (western France) revealed by synchrotron microtomography.

BACKGROUND AND AIMS: Terrestrial plant remains in fossilized tree resin are relatively common. However, histology and preservation of plants entombed in Cretaceous ambers remain poorly known. We report an exquisitely preserved conifer leafy axis from 100-million-year-old opaque amber of western France that is assignable to Glenrosa carentonensis Moreau, Néraudeau, Tafforeau & Dépré. The purpose of this paper is to discuss the taphonomy and the use of microtomography for studies of palaeobotanical remains in amber. METHODS: A leafy axis was examined using propagation phase-contrast X-ray synchrotron microtomography with voxel sizes of 14·9, 1·4, and 0·7 µm. KEY RESULTS: The conifer leafy axis described is preserved in three dimensions. Despite desiccation of the specimen within the surrounding amber, the cuticle, as well as most of inner tissues, is preserved in three dimensions down to the cellular level. Epidermis, palisade parenchyma, spongy parenchyma, transfusion tracheids and vascular bundles are clearly distinguished. CONCLUSIONS: Gross morphology and histology of the specimen were revealed using synchrotron microtomography, allowing an unprecedented resolution for the study of soft-bodied plants entombed in amber. The study reveals a peculiar combination of authigenic and duripartic preservation as well as permineralization, and highlights the complexity of taphonomic processes that can occur in amber inclusions. This fossil demonstrates the difficulty of studying amber-preserved plant remains under certain conditions.

The remarkable stomata of horsetails (Equisetum): patterning, ultrastructure and development.

BACKGROUND AND AIMS: The stomata of Equisetum - the sole extant representative of an ancient group of land plants - are unique with respect to both structure and development, yet little is known about details of ultrastructure and patterning, and existing accounts of key developmental stages are conflicting. METHODS: We used light and electron microscopy to examine mature stomata and stomatal development in Equisetum myriochaetum, and compared them with other land plants, including another putative fern relative, Psilotum We reviewed published reports of stomatal development to provide a comprehensive discussion of stomata in more distantly related taxa. KEY RESULTS: Stomatal development in Equisetum is basipetal and sequential in strict linear cell files, in contrast with Psilotum, in which stomatal development occurs acropetally. In Equisetum, cell asymmetry occurs in the axial stomatal cell file, resulting in a meristemoidal mother cell that subsequently undergoes two successive asymmetric mitoses. Each stomatal cell complex is formed from a single precursor meristemoid, and consists of four cells: two guard cells and two mesogene subsidiary cells. Late periclinal divisions occur in the developing intervening cells. CONCLUSIONS: In addition to the unique mature structure, several highly unusual developmental features include a well-defined series of asymmetric and symmetric mitoses in Equisetum, which differs markedly from Psilotum and other land plants. The results contribute to our understanding of the diverse patterns of stomatal development in land plants, including contrasting pathways to paracytic stomata. They add to a considerable catalogue of highly unusual traits of horsetails - one of the most evolutionarily isolated land-plant taxa.

Surface hydrophobicity of slippery zones in the pitchers of two Nepenthes species and a hybrid.

To investigate the hydrophobicity of slippery zones, static contact angle measurement and microstructure observation of slippery surfaces from two Nepenthes species and a hybrid were conducted. Marginally different static contact angles were observed, as the smallest (133.83°) and greatest (143.63°) values were recorded for the N. alata and N. miranda respectively, and the median value (140.40°) was presented for the N. khasiana. The slippery zones under investigation exhibited rather similar surface morphologies, but different structural dimensions. These findings probably suggest that the geometrical dimensions of surface architecture exert primary effects on differences in the hydrophobicity of the slippery zone. Based on the Wenzel and Cassie-Baxter equations, models were proposed to analyze the manner in which geometrical dimensions affect the hydrophobicity of the slippery surfaces. The results of our analysis demonstrated that the different structural dimensions of lunate cells and wax platelets make the slippery zones present different real area of the rough surface and thereby generate somewhat distinguishable hydrophobicity. The results support a supplementary interpretation of surface hydrophobicity in plant leaves, and provide a theoretical foundation for developing bioinspired materials with hydrophobic properties and self-cleaning abilities.

Study of the Histology of Leafy Axes and Male Cones of Glenrosa carentonensis sp. nov. (Cenomanian Flints of Charente-Maritime, France) Using Synchrotron Microtomography Linked with Palaeoecology.

We report exceptionally well-preserved plant remains ascribed to the extinct conifer Glenrosa J. Watson et H.L. Fisher emend. V. Srinivasan inside silica-rich nodules from the Cenomanian of the Font-de-Benon quarry, Charente-Maritime, western France. Remains are preserved in three dimensions and mainly consist of fragmented leafy axes. Pollen cones of this conifer are for the first time reported and in some cases remain connected to leafy stems. Histology of Glenrosa has not previously been observed; here, most of internal tissues and cells are well-preserved and allow us to describe a new species, Glenrosa carentonensis sp. nov., using propagation phase-contrast X-ray synchrotron microtomography, a non-destructive technique. Leafy axes consist of characteristic helically arranged leaves bearing stomatal crypts. Glenrosa carentonensis sp. nov. differs from the other described species in developing a phyllotaxy 8/21, claw-shaped leaves, a thicker cuticle, a higher number of papillae and stomata per crypt. Pollen cones consist of peltate, helically arranged microsporophylls, each of them bearing 6-7 pollen sacs. The new high resolution tomographic approach tested here allows virtual palaeohistology on plants included inside a dense rock to be made. Most tissues of Glenrosa carentonensis sp. nov. are described. Lithological and palaeontological data combined with xerophytic features of Glenrosa carentonensis sp. nov. suggest that this conifer has been adapted to survive in harsh and instable environments such as coastal area exposed to hot, dry conditions.

The low-temperature method for study of coniferous tissues in the environmental scanning electron microscope.

The use of non-standard low-temperature conditions in environmental scanning electron microscopy might be promising for the observation of coniferous tissues in their native state. This study is aimed to analyse and evaluate the method based on the principle of low-temperature sample stabilization. We demonstrate that the upper mucous layer is sublimed and a microstructure of the sample surface can be observed with higher resolution at lower gas pressure conditions, thanks to a low-temperature method. An influence of the low-temperature method on sample stability was also studied. The results indicate that high-moisture conditions are not suitable for this method and often cause the collapse of samples. The potential improvement of stability to beam damage has been demonstrated by long-time observation at different operation parameters. We finally show high applicability of the low-temperature method on different types of conifers and Oxalis acetosella.

Formation of vacuolar tannin deposits in the chlorophyllous organs of Tracheophyta: from shuttles to accretions.

Most Tracheophyta synthesize-condensed tannins (also called proanthocyanidins), polymers of catechins, which appear in the vacuole as uniformly stained deposits-termed tannin accretions-lining the inner face of the tonoplast. A large body of evidence argues that tannins are formed in recently described thylakoid-derived organelles, the tannosomes, which are packed in membrane-bound shuttles (Brillouet et al. 2013); it has been suggested that shuttles agglomerate into tannin accretions. The aim of the study was to describe the ontogenesis of tannin accretions in members of the Tracheophyta. For this purpose, fresh specimens of young tissues from diverse Tracheophyta were cut, gently lacerated in paraformaldehyde, and examined using light, epifluorescence, confocal, and transmission electron microscopy. Fresh samples were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Our observations showed that vacuolar accretions (1 → 40 µm), that constitute the typical form of tannin storage in tannin-producing Tracheophyta, are formed by agglomeration (not fusion) of shuttles containing various proportions of chlorophylls and tannins.

Development and regeneration ability of the wax coverage in Nepenthes alata pitchers: a cryo-SEM approach.

The morphogenesis of the composite epicuticular wax coverage and regeneration ability of the upper wax layer in Nepenthes alata pitchers were studied using a cryo-scanning electron microscopy. Examination of pitchers of different ages revealed six stages in the wax coverage development. In the first stage, wax crystals resemble those found recently in mature pitches of N. dicksoniana and N. ventricosa. Platelets of the upper wax layer originate from broadened tips of stalks during the last developmental stage. Contrary to previous hypotheses, we found that wax crystals of both layers as well as the stalks connecting them are oriented perpendicularly to the pitcher wall. No changes in the height of the wax coverage were detected in 4-8 weeks after mechanical removal of the upper wax layer from mature pitchers on plants. This indicates that the wax coverage in N. alata pitchers is unable to regenerate.

The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta.

BACKGROUND AND AIMS: Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. METHODS: Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. KEY RESULTS AND CONCLUSIONS: The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.

Quantification of microfibril angle in secondary cell walls at subcellular resolution by means of polarized light microscopy.

The cell walls constitute the mechanical support of plants. Crystalline cellulose building the walls forms rigid microfibrils that set the stiffness of the cell and the direction in which it expands during growth. Therefore, the determination of the directions of the microfibrils is important in both mechanical and developmental assays. We adapted polarized light microscopy to estimate the cellulose microfibril orientations at subcellular resolution. The optical information supplements X-ray scattering data, Raman microspectroscopy, and electron microscopy. We analyzed samples from three plant tissues: cells from an Araucaria excels branch, in which we revealed lower cellulose density in regions where the cell wall curvature becomes bigger, namely, the cell wall corners; a wheat (Triticum turgidum) awn's hygroscopically active region, which revealed a gradient in the cellulose microfibril angles that spans across four cell rows; and a stork's bill's (Erodium gruinum) coiling awn, which revealed that the cellulose in the cell wall is organized in two orientations seamed together, rather than in a continuous helix. The unique spatial information is easily obtained from microscopic specimens and further illuminates new aspects in the mechanical tissues.

Structural and component characterization of meristem cells in Araucaria angustifolia (Bert.) O. Kuntze zygotic embryo.

Araucaria angustifolia, the Brazilian pine, is an endangered native conifer with economic and ecological importance. The female cone develops seeds containing the zygotic embryo, which, at cotyledonary stage, shows well-developed meristems. Little is known about the structure of gymnosperm meristems. In the present work, the composition and morphological organization of Araucaria angustifolia shoot and root apical meristems were studied during embryo development, using histochemical and microscope analyses. Histochemical evaluation revealed the presence of cellulose within the cell wall, cells with the presence of total proteins that react with Coomassie Brilliant Blue, starch grains, and large nuclei with evident nucleoli in the cytoplasm. Scanning electron microscopy showed apical meristem surface morphology, and both scanning and transmission microscopy revealed a thin and irregular cell wall with plasmodesmata and within the cells, mitochondria, many vacuoles, lipid bodies, Golgi bodies, and many amyloplasts with endoplasmic reticulum surrounding them and large nuclei. Similar to angiosperm cells, A. angustifolia meristem cells exhibit pluripotent characteristics, such as apparatus for intercellular communication and differentiation.

Leaf fossils of the ancient Tasmanian relict Microcachrys (Podocarpaceae) from New Zealand.

PREMISE OF THE STUDY: Microcachrys tetragona (Podocarpaceae), endemic to the mountains of Tasmania, represents the only remaining taxon of one of the world's most ancient and widely distributed conifer lineages. Remarkably, however, despite its ∼150 Myr heritage, our understanding of the fossil history of this lineage is based almost entirely on the pollen record. Fossils of Microcachrys are especially important in light of recent molecular phylogenetic and dating evidence. This evidence dates the Microcachrys lineage to the Mesozoic and does not support the traditional placement of Microcachrys as sister to the southeastern Australian genus Pherosphaera. METHODS: We undertook comparative studies of the foliage architecture, cuticle, and paleoecology of newly discovered fossils from the Oligo-Miocene of New Zealand and M. tetragona and discussed the importance of Microcachrys in the context of Podocarpaceae phylogeny. KEY RESULTS: The fossils represent the oldest and first extra-Australian macrofossils of Microcachrys and are described as the new foliage species M. novae-zelandiae. These fossils confirm that the distinctive opposite decussate phyllotaxy of the genus is at least as old as the Oligo-Miocene and contribute to evidence that Microcachrys plants were sometimes important components of oligotrophic swampy habitats. CONCLUSIONS: Leaf fossils of Microcachrys closely comparable with the only extant species confirm that this lineage had a much wider past distribution. The fossil record and recent molecular phylogenetic studies, including that of Microcachrys, also serve to emphasize the important status of Tasmania as a refugium for seed plant lineages.