Pteridophytes with subterranean sexual stages exist in five families. Their prothalli grow underground without light, nourished by fungi, and are rounded, massive, and without chlorophyll. Various authors have suggested that such gametophytes may inhibit outbreeding ability and that minor variations may therefore form in colonies through inbreeding.

This paper questions these ideas. The subterranean condition is believed to be suited to fields, grassy meadows, and other habitats subject to seasonal drying. The parenchymatous thallus makes possible water storage. Water can flow between some particles. Sperm may be carried by mass flow in various directions and can evidently swim as much as 2 cm. Close clumping of underground gametophytes appears to be no less common than in surficial gametophytes and evidence exists that hybridisation occurs.

No evidence has been detected that outbreeding is inhibited, and we conclude that it is successful and that cross-fertilisation is no less common among underground gametophytes than among surface gametophytes. Numerous examples are listed from Lycopodiales, Psilotales, and Ophioglossales.

As empirical relationships between acidic deposition and its effects on soils and surface waters have become increasingly understood, the focus of attention has shifted to the reversal of acidification in response to decreased amounts of acidic deposition.

Recent decreases in acidic deposition, in both North America and parts of Europe, have initiated the reversal of acidification and the recovery of impacted ecosystems. Reversal has also been investigated in large-scale experiments with whole ecosystems. Predictive models can account for much of this empirical and experimental data, at least at the catchment scale, over periods of years.

Discrepancies between observed and predicted effects are attributable in part to the increasingly important role of nitrogen in soil and water acidification. ‘Nitrogen saturation’ threatens to offset the incipient recovery following decreases in SO2 emissions. Future climate change might further exacerbate the problem by increasing the rate of mineralisation of soil organic matter and releasing stored nitrogen.

The Bunsen-Roscoe law states that the effect of radiation is always the same regardless of the variation in the intensity or in the time of radiation as long as the product of the two is kept constant. This law holds true for many ordinary physico-chemical reactions over a wide range of intensities. The present investigation was undertaken to test the validity of the Bunsen-Roscoe law by studying the frequency of (1) sex-linked lethal mutations and (2) translocations in Drosophila melanogaster at much lower intensities of radiation than those previously tried.

In the course of our studies of reproduction of Calanus finmarchicus under laboratory conditions we noticed that all the eggs produced in our cultures were lying on the bottom of the glass dishes, and when transferred into fresh culture medium (“Erdschreiber”) or sea-water sank down relatively very rapidly. As the eggs were fertilised and healthy, and a large proportion of them developed into active nauplii (Raymont and Gross, 1942), it was obvious that the density of the living egg was considerably higher than that of sea-water.

The identity and abundance of animals passing through a 1·0 mm mesh but retained on a 0·5 mm mesh is detailed for a number of seabed samples of medium, fine and very fine sand taken in the Beatrice Oilfield in 1981. Comparisons are made with the corresponding 1·0mm-sieved fractions, and the effects on community parameters of combining the two data sets are considered.

In general fewer animals were found on the 0·5 mm mesh than on the 1·0 mm mesh above it. The 0·5 mm mesh samples added comparatively few taxa to the faunal list of the survey. The quantitatively-scored taxa from the 0·5 mm mesh were therefore essentially a sub-set of those already recorded on the 1·0 mm mesh. Several taxa of Foraminiferida were found only on the 0·5 mm mesh, and one of these appeared to be relatively abundant. However. Foraminiferida were not scored quantitatively in this study.

In all samples, when 0·5 mm and 1·0 mm data were combined an increase was noted in the number of taxa recorded compared with 1·0 mm data alone. This recruitment of taxa was largely a reflection of the greater number of individuals in the combined data, rather than the inclusion of taxa unique to the 0·5 mm material. Similarly, the improved precision of abundance estimates of dominant taxa in replicate samples in the combined data probably resulted from the greater number of individuals included in the analysis.

It is argued that the choice of a particular mesh size imposes an essentially arbitrary cut-off along the size spectrum of benthic organisms. A 1·0 mm mesh has been found to yield adequate data in a number of offshore surveys undertaken by the Oil Pollution Research Unit (OPRU). Although a greater number of animals per sample is collected by sieving on a 0·5 mm mesh, the time taken to extract and identify this material must be considered. The alternative of spending an equivalent time analysing extra 1·0 mm samples may in fact yield a greater increase in confidence in the results.

The immature stages of C. circumscriptus Kieff. are found in the mud of most Scottish salt marshes. The life cycle has been studied by means of laboratory cultures and by observation and periodic sampling at a salt marsh near Dumbarton. Data are given concerning the life cycle in the laboratory and out of doors. In the field there are two generations a year.

In captivity the female lays a single large batch of eggs which adhere to the substrate by means of structures on the chorion. The eggs and the manner of oviposition and hatching are described. Descriptions of the larvae, supplementing those of previous authors are given. The first instar differs from older larvae in possessing a retractable prothoracic proleg, and is more sluggish in its movements, probably remaining near the oviposition site until the first ecdysis. Before pupation the larva comes to the surface. This is necessary for successful pupation, enabling the pupa to breathe and to form the buoyancy space. The pupa buries itself in the mud emerging only under flooded conditions to float on the surface or prior to ecdysis.

The structure of the sublittoral benthic macro-invertebrate populations of the Forth estuary and firth, Scotland, is described, giving the species richness, abundance and biomass for the area from the freshwater tidal limit to the North Sea boundary. Eight faunal associations have been defined, which include classical Petersen communities in the marine area and transition associations within the estuary. The spatial distributions of the associations are predominantly the result of the physical environment, but superimposed on the effects of salinity, sediment type and bathymetry are the effects of urbanisation, industrialisation, dredging and spoil disposal and thermal discharges. The benthos of the major part of the firth has been little affected, although that of the peripheral and estuarine areas does show anthropogenic effects.

The water column-benthos and fisheries-benthos interactions are also discussed. Elevated levels of nutrients in the water column may be the cause of enriched benthic populations in the firth and an assessment of the fish-benthos coupling indicates an estuarine functioning similar to other northwestern European areas.

Lochs Fyne and Striven are deep-silled fjords opening into the northern Firth of Clyde. They receive relatively little freshwater from local runoff, have a relatively low rate of tidal exchange, and undergo periods of deep water stagnation. Both contain fish farms which have lost stock because of phytoplankton blooms. Loch Striven was investigated in detail in 1980. Observations are also reported for 1979 and 1981, and for Loch Fyne from 1980–1982. Most stratification in Striven is due to salinity layering, but most of the freshwater in the loch probably originates in the Clyde Estuary and is associated with high concentrations of nitrate. Typical phytoplankton biomasses in Striven are the same as those in the western seaboard Loch Creran, but maxima exceed those in Creran. In addition to a red tide of Gyrodinium aureolum in September, 1980, three periods of high biomass seem to be a regular feature of the phytoplankton calendar in Striven. The spring increase takes place in March or early April, is dominated by the diatom Skeletonema costalum, and probably depends on the stabilizing effects of reduced near-surface salinities. A summer flourishing of Leptocylindrus danicus and dinoflagellates is also associated with near-surface salinity layering. A late spring bloom of diatoms, dinoflagellates and small flagellates, some ichthyotoxic, appears to be related to the occurrence of thermohaline stratification and near-surface nutrient depletion; on some occasions lochhead upwelling may also have been involved. Insofar as data are available, the ecology of phytoplankton in Loch Fyne appears similar to that in Loch Striven.

The discovery in 1941 (Auerbach and Robson, first published in 1946) that mustard gas (β-β′-dichloro-diethyl-sulphide), (ClCH2.CH2)2S, is comparable to X-rays in its capacity to produce mutations and chromosome rearrangements naturally raised the question as to what special properties of mustard gas enable it to act in this manner. There are indications (Auerbach and Robson, 1947) that the mutagenic effects of mustard gas are due to a direct action on the chromosomes, and not to an indirect one via the cytoplasm. This suggests that a selective and specific chemical reaction occurs between mustard gas and the genie material. It appeared possible that a systematic survey of substances chemically related to mustard gas might reveal a chemical group or structural arrangement responsible for the mutagenic action. This in its turn might also throw some light on the other component of the reaction, the gene or chromosome, and on the process of mutation itself.

The substances, to be tested were, with one exception, chosen on account of their chemical and pharmacological similarity to mustard gas. They were:

(1) N-methyl di-(2-chloroethyl) amine, CH3.N(CH2.CH2Cl)2, one of the so-called nitrogen mustards. This is a liquid with strong vesicant action. It decomposes fairly rapidly in water. Its hydrochloride is a solid, soluble in water and forming a stable solution. This solution proved useful in certain tests in which it was convenient to apply a mutagenic substance in aqueous solution.

Much attention has been paid to euphausiids or krill because of their value as indispensable food of baleen whales and commercially important fish both in the North Atlantic and North Pacific and more recently attempts to exploit euphausiids for human consumption were undertaken in the Antarctic, North Pacific and in the Norwegian fjords.

It is proposed that the Pteridophyta are in many ways the plant kingdom's equivalent of the Amphibia. The biology of these two groups is compared from points which have arisen in this Symposium on the Biology of Pteridophytes. Some areas of possible future development in pteridophyte biology are then suggested.

Picea sitchensis has a haploid complement of twelve metacentric or submetacentric chromosomes which are similar to each other in size. Prominent secondary constrictions, which are probably the sites of nucleolus organisers, occur on five chromosomes (N.O.R.s). The DNA content of the haploid, unreplicated chromosome set is 9 × 109 nucleotide pairs and, in spite of earlier claims, probably does not vary significantly between different populations. B-chromosomes occur extensively in the southern half of the species range. They have little effect on growth rate but delay the time of ♂ and ♀ flowering. Meiosis starts and ends in spring, taking about twenty-two days to complete. The B-chromosomes do not pair at meiosis and appear to be distributed at random. There is marked accumulation of B-chromosomes when transmitted through the ♀ parent, possibly due to preferential segregation during meiosis. A balance between gain by accumulation and loss due to delay of flowering may account for the natural distribution of the B-chromosome.

Investigation of a temperate and tropical beach has shown that, based on chlorophyll a analyses, an epipsammic diatom population present in the temperate beach is absent in the tropical beach. Comparison of community respiration rates for the two beach populations excluding macrofaunal respiration shows that the tropical beach rates (which were constant over the period January-March) were about 9 times the winter rates of the temperate beach and about twice the summer rates. Annual microbial production is estimated at 15 gC/m2 for the temperate beach and 72 gC/m2 for the tropical beach. The greatly increased rate of production in the tropical beach was considered to be a function of increased water flow into that beach. In comparison, meiofauna and macrofauna biomass are less in the tropical beach and their respective production likely to be at most no more than in the temperate beach. It is proposed from experimental studies that the failure of animal populations fully to utilise microbial production in sandy beaches is due to the relative degree of exposure stripping significant quantities of microbial growth from this system. This proposal is discussed as a means of explaining mechanisms of control of animal production in sandy beaches.

Brief exposure in the young stage to carbon monoxide in concentration c. 1 per cent modifies subsequent sex expression in male plants of the dioecious Cannabis sativa (hemp), inducing the formation of intersexual or even functionally female flowers. The effect is registered in flower primordia of a particular age; older ones are already sexually committed, and younger ones apparently recover from treatment to pursue the genetically established path of ontogeny. Grafting experiments show that the stimulus is retained in the apex even when it is transferred to an untreated plant before the flower primordia have begun differentiation.

The effect of carbon monoxide in modifying sex expression is similar to that induced by auxin administration, and it is possible that the basic function of the gas at the effective concentrations is to upset auxin metabolism in treated tissues, perhaps by inhibiting enzyme systems normally responsible for regulating endogenous auxin levels.

We studied the effects of oxygen (aerated versus O2 depleted ∼0.5 mg 1−1 O2) and nitrate (none versus 10 μmol 1−1) on the ammonium uptake kinetics and adenylate pools in two wetland plants differing in their degree of flood tolerance (Phalaris arundinacea L. and Glyceria maxima (Hartm.) Holmb.). The study was performed as a random block design in a growth chamber. The -uptake kinetics were estimated by using a computerised nonlinear parameter estimation procedure to fit the differential form of a modified Michaelis–Menten model to solution depletion curves. The uptake kinetics for differed between the two species: Vmax was significantly higher for P. arundinacea (24.7 to 29.6 μmol h−1 g−1 root dry weight) than for G. maxima (4.6–10.3 μmol h−1 g−1 root dry weight). The concentration at which uptake ceases (Cmin) was 0.2 to 0.5 μmol 1−1 for P. arundinacea and significant higher (1.1–2.7 μmol 1−1) for G. maxima.Km varied between 3.1 and 6.2 μmol 1−1 for P. arundinacea, and 1.6 and 3.0 μmol 1−1 for G. maxima. The different uptake kinetics of the two species reflect the different structure of their root systems: P. arundinacea has an extensive root system consisting of many thin roots whereas G. maxima has fewer but thicker roots. The uptake kinetics also suggest that P. arundinacea is adapted to growing at lower ambient concentrations than G. maxima. Oxygen had no consistent effect on uptake kinetics. However, the plants that had in the nutrient solution as well as had slightly higher Vmax values and lower Cmin and Km values than those without . Thus, both species were able to sustain their uptake characteristics at low external O2 concentrations, probably because of internal aeration through the air-space tissue of the plants. Nitrate deprivation also lowered the energy charge ratio and adenine nucleotide content in roots. The roots recovered quickly from deprivation once was resupplied. The stresses imposed by partially O2-depleted conditions and lack of nitrate were therefore relatively mild and reversible. It seems that the inherent aerenchyma development under aerated conditions in these species is sufficient to maintain adequate root oxygenation under partially O2-depleted conditions.

The general environmental factors controlling the epiphytic vegetation on birch are discussed, as is the physio-chemical nature of birch bark as a substratum for epiphytes (especially lichens). In terms of species diversity, birch is found to be a poor host (phorophyte) for epiphytes and various reasons (e.g. low bark pH) for this are suggested. The lichen communities commonly encountered on different parts of a birch tree in different situations in the British Isles are summarized. Annotated appendices provide lists of the lichens (235 species) and bryophytes (58 species) recorded on Betula in the British Isles.

The paper deals with three problem areas in the taxonomy of British willows: (1) the widespread occurrence in Perthshire and neighbouring counties of an intermediate between Salix myrsinifolia Salisb. and S. phylicifolia L., apparently of hybrid origin, though growing in an area where typical S. phylicifolia has yet to be found; (2) the complex taxonomy of the British Sallows, where two common aggregate species, Salix cinerea L. and S. caprea L., are each represented by two segregates; a third, S. aurita L., may also comprise more than one segregate; all three species interbreed, as do the segregates within each aggregate; (3) the disputed identity of the Crack Willow, Salix fragilis L., and its nomenclatural implications.

Sitka spruce grown from seed has a juvenile phase of about twenty years before coning commences; mature trees and grafted scions cone intermittently and produce good cone crops every three–five years. These characteristics have lengthened the breeding programme and reduced seed production in orchards. Production of male and female cones can be enhanced by treatments such as heat and drought and by application of a mixture of gibberellins A4 and A7 (GA4/7) to mature grafts. To enhance flowering consistently in container grown grafts the GA4/7 must be applied together with a cultural treatment, but with larger grafts in the field GA4/7 alone is often effective. Attempts to induce cone production in juvenile trees, however, have been less successful. Female cones initiated on field grown trees in response to inductive treatments yield seed of a similar quantity and quality to that from cones on untreated trees. The physiological mechanisms of coning, and cone induction techniques, are discussed.

The evolutionary significance of natural fire disturbance regimes in the development of post-fire fungal and herb communities is examined. Before a fire the soil microflora exhibits a general fungistasis, microbial competition is great, nutrients are limiting, and carbonicolous ascomycetes are in a dormant phase. Also in mature chaparral shrub communities the soil microflora is implicated in soil toxicity that prevents seeds of some species from germinating in the interval between burns. Fire results in the deposition of ash and charred wood, a release of nutrients, the elimination of competitors (e.g. shrub cover, soil microflora), an increase in soil alkalinity, the removal of soil toxicity/fungistasis, and cues the germination of constitutively dormant ascospores and seeds. The cue for germination of the chaparral fire annuals appears to be components of the hemicellulose fraction, produced during the charring of wood, but this fraction has not been tested for its ability to cue ascospore germination. Germination in the absence of fire would be “suicidal” because neither the carbonicolous ascomycetes nor the post-fire annuals are able to compete successfully in these pre-burn habitats. The frequency of burning and the uneven heating of the soil surface creates patchiness with a corresponding increase in the species richness of the post-burn community.

The main pollutants affecting materials are sulphur dioxide and sulphates, nitrogen oxides and nitrates, chlorides, carbon dioxide and ozone. In marine environments it is important to separate the effects of anthropogenic pollutants from marine sources of the same substances. The effects of paniculate matter, especially from diesel vehicle emissions is of increasing significance.

In buildings containing books, historical artefacts or other works of art indoor pollutants may cause significant degradation. These pollutants may either be lower concentrations of pollutants originating outdoors or other substances generated from synthetic materials, paints, varnishes and display cases as well as from combustion for heating.

The materials most sensitive to pollutants are calcareous building stones and ferrous metals. Manifestations of damage include losses of mass, changes in porosity, discoloration and embrittlement. In the case of stone it is difficult to (1) dissociate the effects of historical concentrations of pollution from current ones and (2) to establish background rates of erosion or decay in the absence of pollutants.

Damage to materials in polluted atmospheres can be attributed to dry or wet deposition of pollutants, or dissolution in rainfall in the case of stone. Estimates of the contributions of the different mechanisms of decay have been made in programmes in the U.S.A. and the U.K.

To obtain estimates of the economic cost of damage from acid deposition it is necessary to know how decay rates are related quantitatively to pollutants and meteorological parameters (damage functions), and the distribution of materials exposed in buildings and in geographical areas. There are few damage functions available and those in existence lack general applicability. There is. therefore, much importance attached to national and international exposure programmes that have been established to assess the responses of a range of materials to different environments. Such work is also of interest in predicting the potential effects of climatic changes on materials.

Methodologies have been developed to enable estimates of economic costs of damage to be made. These are being refined with better data on rates of decay obtained from mathematical models and from exposure programmes. The concept of target loads for damage, originally devised for the natural environment, is being introduced to help assess the action needed to reduce degradation of sensitive materials and buildings.