Considerable interest attaches to the unravelling of the complete life-history of the Psilotaceæ, since they are apparently the nearest living representatives of the Sphenophyllales.

The recent description of the gametophyte of Tmesipteris by Prof. Lawson, whose figures 1 had the privilege of seeing before they went to press, and the discovery of the gametophyte of Psilotum, which is the subject of the present paper, form a first contribution to the solution of this problem. It is of some interest to note that there remains now no Pteridophyte the gametophyte of which has not been described.

In the early part of this research I was fortunate in finding a locality near at hand in which Psilotum flourished, and therefore I had at my disposal abundance of spores and later numerous prothalli.

The lead isotope compositions of 61 galenas from central and southern Scotland vary markedly between different regions. Most galenas from the southern Grampian Highlands yield isotope ratios (206Pb/204Pb 17·77 ± 0·25, 207Pb/204Pb 15·47 ± 0·05, 208Pb/204Pb 37·63 ± 0·26) less radiogenic than those from Midland Valley galenas (18·22 ± 0·12, 15·55 ± 0·05, 38·13 ± 0·14) whilst galena lead from the Southern Uplands (18·28 ± 0·12, 15·56 ± 0·03, 38·21 ± 0·18) is more radiogenic than that from the southern Midland Valley (18·12 ± 0·06, 15·52 ± 0·02, 38·06 ±0·10). The change in isotopie composition across the Highland Boundary fault reflects the presence or absence of Dalradian rocks which included a magmatic component of lead. Galenas from the Dalradian sequence in Islay, where igneous rocks are lacking, have a composition (18·14±0·04, 15·51±0·01, 37·90±0·02) more like Midland Valley galenas. In the Southern Uplands, galenas yield lead isotope ratios similar to those of feldspars from Caledonian granite (18·30 ± 0·14, 15·57 ± 0·04, 37·96 ± 0·15) analysed by Blaxland et al. (1979). The similar ratios reflect the incorporation of Lower Palaeozoic sedimentary rocks into the granite magma, rather than a granitic source for the mineralisation. The granites were then thermal-structural foci for later mineralising fluids which leached metals from the surrounding rocks. Within the Midland Valley, galenas hosted in Lower Devonian-Lower Carboniferous lavas are notably more radiogenic (18·31 ±0·12, 15·58 ± 0·06, 38·20 ± 0·16) than sediment-hosted galenas (18·14 ± 0·07, 15·52 ± 0·02, 38·08 ± 0·10). The Devonian lavas at least may have inherited lead from subducted (? Lower Palaeozoic) rock incorporated in the primary magma.

Plesiosiro madeleyi Pocock, 1911, the monotypic representative of the fossil order Haptopoda Pocock, 1911 from the British Middle Coal Measures (Upper Carboniferous, Westphalian B) of Coseley, Staffordshire, is redescribed. A specimen from Sparth Bottoms, Lancashire is not a Plesiosiro and is referred to Arthropoda incertae sedis. Plesiosiro was probably a predator, having tooth-like projections on the femora for prey capture, and shows adaptations of the limbs for crawling in narrow spaces. The uncertain nature of the chelicerae, eyes and respiratory organs makes resolving the phylogenetic position of Plesiosiro difficult, though Haptopoda deserves its status as a separate order. Plesiosiro resembles both cythophthalmid and trogulid opilionids. Its broad prosoma–opisthosoma junction could be interpreted as a synapomorphy for Plesiosiro + Opiliones, but this character is not unique to these orders. Alternatively, Plesiosiro has a large, ventral opisthosomal sclerite. This is interpreted here as a genital operculum, a synapomorphy for Tetrapulmonata, and Plesiosiro is tentatively referred to this clade. Based on the synapomorphies of a divided sternum and subdivided telotarsi a relationship of the form: (Plesiosiro (Amblypygi (Thelyphonida + Schizomida))) is proposed.

The Mucorales have a wide geographical distribution and for seventy years they have been the subject of investigation both in Europe and in America. In this country, however,little research has been done on this group, the only workers being Bayliss-Elliott (1930) who has investigated the microflora of the Dovey salt marshes, Dale (1912, 1914) who examined the fungus flora of soil at Cambridge, and Brierley (1923, 1927, 1928) who has done considerable work on soil study. Although certain of the Mucorales were isolated by the last named, he was mostly concerned with the general methods of soil culture. The important quantitative technique was devised by Brierley (1927). Oudemans and Koning (1902) were the first to show the presence of Mucors in the soil. They examined the soil fungi in Holland and isolated two new species of Mucors. Möller (1903) investigated the fungi found in Pine mycorrhiza and obtained a further four new species. Hagem (1907, 1910) studied the morphology and physiology of seventeen Mucors from the soil of Norway, seven of which were new species. In 1908 Lendner published his “Les Mucorinées de la Suisse,” an important contribution to the study of this group of fungi. A criticism which might be levelled at this work is that it is difficult to ascertain from it whether or not Lendner used pure cultures on which to base his descriptions. He merely states that “dilution methods used in Bacteriology were employed,” no mention of monospore cultures being made. Further important work on this group has been done by Korpatschewska (1909), Namy-slowski (1906, 1920), Naumov (1914, 1924, 1935), Ling-Young (1930), Johann (1932), Jensen (1912, 1931), and in the Kryptogamenflora der Mark Brandenburg (1935) Zycha gives a complete revision of the classification of the Mucorales. A survey of the geographical distribution of this group of fungi is found in the work of Niethammer (1935), while further classification has been done by Linnemann (1936). In America, Povah (1917) and Waksman(1916, 1917, 1922, 1927) have both added considerably to our knowledge of the Mucorales in the soil.

In 1861, in a part of the province of Otago, New Zealand, not previously botanically explored, I made, among other botanical collections, one of Lichens and Fungi. The number of new species and varieties proved to be considerable, amounting to about 20 per cent. of the whole lichens, and 40 per cent. of the whole fungi, collected. Since my return home, I have submitted (with a view specially to the study of the minute anatomy of the reproductive organs and their contents) the new species (and varieties) in question—some of them repeatedly—to microscopical examination: the results whereof are contained in the notes which follow.

In the year 1818, my attention was accidentally directed to the subject of water in crystallised bodies, by the explosion of a crystal of Topaz, which I had exposed to a red heat, for the purpose of expelling its colouring matter. This violent disruption of the specimen, which was shivered into a thousand films, of extreme tenuity, arose from the expansion of the imprisoned fluid, and induced me to institute a series of experiments, for the purpose of determining the nature of the fluid, the form of the cavities which contained it, and the arrangement of these cavities in reference to the crystalline form of the mineral.

The early actinopterygian Mesopoma planti is reassigned to a new genus on the basis of data obtained from high-resolution computed tomography (CT) scans of an unusually well-preserved specimen from the Early Pennsylvanian of Lancashire, UK. The former M. planti is joined by two further Mesopoma species from the Late Mississippian of Scotland. CT scans of the key planti specimen bring to light new details of the dermal skull, pectoral girdle and fin. Among the cranial features, CT data reveal a specialised, anteriorly projecting preopercular bone, the location of the spiracular duct opening, presence of a so-called coronoid process on the lower jaw and the full three-dimensional shape of the snout. Of the pectoral girdle and fin, for the first time in a Palaeozoic actinopterygian it has been possible to complete a three-dimensional reconstruction of the entire endoskeleton in articulation. The fin presents new diversity within a conservative general pattern, revealing for the first time a double propterygium. Girdle shape shows that the fin orientation is derived: rotated with the leading edge dorsalmost. These details are used to identify unexploited character states for use in phylogenetic analyses, while functional implications of the fin and girdle suggest advanced locomotory control emerging among different groups of post-Devonian ray-finned fishes.

Specimen-level phylogenetic approaches are widely used in molecular biology for taxonomic and systematic purposes. However, they have been largely ignored in analyses based on morphological traits, where phylogeneticists mostly resort to species-level analyses. Recently, a number of specimen-level studies have been published in vertebrate palaeontology. These studies indicate that specimen-level phylogeny may be a very useful tool for systematic reassessments at low taxonomic levels. Herein, we review the challenges when working with individual organisms as operational taxonomic units in a palaeontological context, and propose guidelines of how best to perform a specimen-level phylogenetic analysis using the maximum parsimony criterion. Given that no single methodology appears to be perfectly suited to resolve relationships among individuals, and that different taxa probably require different approaches to assess their systematics, we advocate the use of a number of methodologies. In particular, we recommend the inclusion of as many specimens and characters as feasible, and the analysis of relationships using an extended implied weighting approach with different downweighting functions. Resulting polytomies should be explored using a posteriori pruning of unstable specimens, and conflicting tree topologies between different iterations of the analysis should be evaluated by a combination of support values such as jackknifing and symmetric resampling. Species delimitation should be consistent among the ingroup and based on a reproducible approach. Although time-consuming and methodologically challenging, specimen-level phylogenetic analysis is a highly useful tool to assess intraspecific variability and provide the basis for a more informed and accurate creation of species-level operational taxonomic units in large-scale systematic studies. It also has the potential to inform us about past speciation processes, morphological trait evolution, and their potential intrinsic and extrinsic drivers in pre-eminent detail.

The opportunities for observation were afforded by the voyage and subsequent drift of the S.Y. Endurance. During December 1914 and January 1915 for a period of six weeks she successfully bored her way through pack-ice of every description—drift-ice, open-pack, and very frequently even close-pack. Continually fighting, she penetrated from 59° to 72° S. lat., and finally reached the land water off Coats Land on the latter parallel. As the crow flies, therefore, she was navigated through ice for nearly 800 geographical miles on this voyage; her actual course among the ice-fields and floes was computed to exceed 2000 miles, an achievement without parallel in the Antarctic. The principle adopted was to keep to the east, where presumably there is less pack than in the west; if the Endurance experience is a normal one, however, the meridian of 20° W. long., which was followed, is certainly not far enough east.

Although sophisticated geochemical studies tell us that tonolite-trondhjemite-granodiorite (TTG) plutonic complexes must be formed by partial melting of metabasaltic source material, they cannot tell us the tectonic regime in which this crust was formed, nor how large volumes of TTG magma can be generated. This study suggests that a solution to TTG arc crust formation requires a strongly interdisciplinary approach, to resolve the tectonic setting (slab melt verses mafic lowermost crust sources), the time and length scales for melting and extraction, and the role of melt segregation mechanisms in the formation of both Archean TTGs and more recent adakite-like magmas. The aim of this paper is to present an experimental approach which, when coupled with numerical models, allows some of these issues to be addressed. The experiments are designed to reproduce the local changes in bulk composition that are predicted to occur in response to buoyancy-driven melt segregation along grain edges and associated compaction of the solid residue. The preliminary study presented here documents the changes we observe in the melt composition and melt and solid phase modes between earlier direct partial melting and the new segregation equilibration experiments on metabasalt bulk compositions. The results suggest that if dynamic melt segregation and equilibrium processes are active, they may modify the normally robust geochemical indicators, such as Mg-numbers, which are typically used to develop models of TTG petrogenesis.

The Vittarieæ, as described by Christensen, comprises five genera, viz. Vittaria, Monogramma, Antrophyum, Hecistopteris, and Anetium, all of which are epiphytic forms growing in the damp forests of the Old and New World Tropics. All of them possess creeping rhizomes on which the fronds are arranged more or less definitely in two rows on the dorsal surface. The fronds are simple in outline, with the exception of those of Hecistopteris which are dichotomously branched. The venation of the fronds is reticulate, except in Hecistopteris where there is an open, dichotomous system of veins, and in Monogramma, in some species of which the venation consists simply of a mid-rib. An interesting feature, which has proved to be valuable as a diagnostic character, is the presence of “spicule cells” in the epidermis of the fronds. These spicule cells are elongated cells containing spicules of silica, and their presence appears to be universal in the Vittarieæ. The sporangia are fairly constant in form through-out the group, but their distribution is extremely varied. The roots are characteristically provided with very numerous reddish-brown root hairs, a character shared with other epiphytic Ferns. The Gametophyte is divergent from the common cordate type in all cases where it has been investigated. Such are the main external characteristics of the group under consideration.

Loch Fleet is an upland loch in SW Scotland, distant from significant local pollution, and unlikely to be affected by changes during the five-year project. The underlying geology is granitic. The 111 ha catchment is 90% moorland, dominated by heather and flying bent; 10% is planted with conifers.

Rainfall is approximately 2200 mm per year, predominantly from W and SW. More than half of rain events are pH>4·7; mean pH is 4·84 (1985). Marine salts are the major solutes. Deposition of acidity is about 0·1 g H+ m−2 per year, about twice that of eastern Scotland; deposition of non-seasalt sulphur is 1·6 g S m−2 per year. Soils are shallow and comprise organic peats, peaty gleys, and peaty rankers; base saturation is 3–19%. Soils (pH 2·5 to 4·6) are most acid in the forested area.

The loch is more acid (×5) than bulk deposition; additional acidity is mobilised from soils by the predominantly (>90%) superficial drainage. Moorland drainage dominates; that from the forest is more acid, but very variable in quantity and composition.

Catchment interventions in 1986 and 1987 are designed to alter the chemistry of drainage waters and the loch, so that the fishery can be restored. In addition to the work reported, extensive soils, sediment and biological investigations are underway.

The loop configuration, structure and growth are studied in a series of megathiridoid dorsal valves ranging in length from 0·7 to 6 mm. The structure of the posterior and anterior sectors of the descending lamellae and their relationships with the socket ridges, dorsal septa and dorsal valve floor, are studied, illustrated and described. Detailed studies show that internal structures display great variability. In the megathiridoids the lamellae of more typical terebratulide loops are replaced by partially developed loops in early developmental stages, resulting in a mix of free sections of loop together with sections where the lophophore rests directly on the epithelium of the valve floor. Comments on the ecology of the megathiridoid species are included and relate their unusually wide gapes, which position their lophophores fully accessible to the open sea, with their strong lophophore attachments and loss of typical free loops. The new genus Joania (type species Terebratula cordata Risso, 1826) is erected for those Argyrotheca which, although having a typical megathiridoid brachidium, differ in their adult crural development, their narrow hinge line, their prominent cardinal process, their characteristic dorsal median septum and their tuberculate radial ridges terminating anteriorly in tubercles.

A diversity of filamentous microfungi was discovered from thallus surfaces of epiphytic lichens preserved in Bitterfeld and Baltic amber. We report seven distinct morphologies of dematiaceous hyphomycetes, some of which closely resemble species of the extant genera Sporidesmium, Taeniolella s. lat. and Taeniolina. Both the placement of the fungi on their substrates and the exquisite preservation of delicate structures indicate that the fungi were fully developed before they were engulfed by fresh resin. The lichens probably grew on the trunks of resin producing trees and became embedded in resin flows together with their fungal associates. The findings demonstrate that a wide range of presumably specialised fungi have lived on living and decomposing lichen thalli at least since the Paleogene. The findings add an interesting new component to the as yet poorly known mycota of the ancient European amber forests.

Cell culture systems have been developed to assess the potential pathogenicity of mineral dusts. The in vitro cytotoxicities of a variety of dusts towards mouse peritoneal macrophages, Chinese hamster lung cells (V79 cell line) and human alveolar type II cells (A549 cell line) were investigated.

Non-pathogenic dusts were found to be inert in vitro. Fibrogenic non-fibrous dusts such as silica were only cytotoxic towards macrophages. Fibrous dusts which are both fibrogenic and carcinogenic in vivo are cytotoxic towards all three cell types, their cytotoxicity being dependent on fibre size. The size range important for the observed biological effect is longer than about 8 μm and thinner than about 1·5 μm.

Granite is the final product of the high-temperature, magmatic, predominantly endogenic, chemical differentiation of the earth. Our understanding of the origin and evolution of granitoid rocks comes from a combination of direct observation, analogue experimentation and numerical modelling. A brief historical overview shows an exceptional level of such research activity over the last 50 years. The number and complexity of questions have resulted in both an absolute and a relative growth of the science since the plate tectonic revolution, largely consisting of refining the current magmatic paradigm within its overarching context. Current research activity involves large components of mineralogical–petrological–geochemical and structural–tectonic work, with much lower levels of experimental, geophysical and geochronological investigations. Many important questions concerning the thermal, physical and chemical aspects of the origin and evolution of granites remain. In keeping with the general progress of science, the complexity of the questions, the declining financial support and the revolution in information technology, directions of granite research in the foreseeable future will change from concrete and qualitative to abstract and quantitative, from expensive and active to cheap and armchair, from reductionist to holistic, and from periodic communication to continuous communication.

The present study explores the macroevolutionary dynamics of shape changes in the humeri of all major grades and clades of early tetrapods and their fish-like forerunners. Coordinate point eigenshape analysis applied to humeral outlines in extensor view reveals that fish humeri are more disparate than those of most early tetrapod groups and significantly separate from the latter. Our findings indicate sustained changes in humeral shape in the deepest portions of the tetrapod stem group and certain portions of the crown. In the first half of sampled tetrapod history, subclades show larger than expected humeral disparity, suggesting rapid diffusion into morphospace. Later in tetrapod evolution, subclades occupy smaller and non-overlapping morphospace regions. This pattern may reflect in part increasing specialisations in later tetrapod lineages. Bayesian shifts in rates of evolutionary change are distributed discontinuously across the phylogeny, and most of them occur within rather than between major groups. Most shifts with the highest Bayesian posterior probabilities are observed in lepospondyls. Similarly, maximum likelihood analyses of shifts support marked rate accelerations in lepospondyls and in various subclades within that group. In other tetrapod groups, rates either tend to slow down or experience only small increases. Somewhat surprisingly, no shifts are concurrent with structural, functional, or ecological innovations in tetrapod evolution, including the origin of digits, the water–land transition and increasing terrestrialisation. Although counterintuitive, these results are consistent with a model of continual phenotypic innovation that, although decoupled from key evolutionary changes, is possibly triggered by niche segregation in divergent clades and grades of early tetrapods.

The postcranial skeleton of Ariekanerpeton sigalovi (Seymouriamorpha: Discosauriscidae; Lower Permian, Tadzhikistan) differs from that of like-sized Discosauriscus specimens in showing: wider interclavicle anterior plate with smaller, rhomboidal sculptured field on its ventral surface not reaching plate posteromedial margins; broader interclavicle plate-stem junction; slightly narrower interclavicle posterior stem; anteroposteriorly narrower clavicle ventral plate with convex posterior margin; shorter, more robust humerus; four phalanges on fourth manus digit (five phalanges in Discosauriscus); ilium more elongate dorsoventrally with anteroposteriorly narrower neck; posterior process of iliac blade oriented distinctly posterodorsally rather than horizontally; more gracile atlantal rib; broadened distal end of second presacral rib. A revised cladistic analysis of the best known seymouriamorph species retrieves Ariekanerpeton either as sister group to both species of Discosauriscus, or to D. austriacus only.

Granites and their associated extrusive rocks are formed in large volumes whenever the continental crust is heated by rising hot mantle, or thickened by collision processes. The complexity of rocks of the granite family is related to the complexity of the continental crust itself and the complexity of processes which lead to thermal perturbations. The light continental crust acts as a density filter which screens out heavy mantle magmas and leads to complex underplating and magma mixing processes. Perhaps the primary cause of crustal melting is the deep recycling of volatiles which are fixed in the oceanic crust before subduction. Modern studies of subduction and collision processes show the large scale and complexity of processes which modify old continental crust.

If such tremendous agents did in reality exert their influence in the Alps, it is not conceivable that other countries, situated lower, and composed of materials much more frail, could have been spared. We hear in fact of similar traces, more or less distinct, in all quarters of the globe. From the bones of animals, natives of the hottest climates, which are found over a frozen region of vast extent in the Russian empire, Pallas concludes, that an enormous torrent had transported their carcases across the ridge of Tartary.