The watermark disease is caused by the bacterium Erwinia salicis. It affects six species of tree willow and of these the white willow (Salix alba) and certain of its varieties are particularly susceptible. Unusually for a bacterial disease, the pathogen only colonises the xylem tissues, which become discoloured as a result. Watermark causes severe losses in S. alba var. caerulea, the cricket bat willow, and in several Dutch clones of S. alba which have been widely planted in that country. Although numerous studies have been made of its epidemiology since the disease was first reported in 1924, the infection process remains clusive. Recent research, much of it unpublished, points to the widespread occurrence of symptomless infection, and the possible role of this in the transmission of disease through the propagating material.

Acid rain has been one of the first and longest running of the multi-national environmental issues. The phenomenon was described in the 1950s and 60s by noted scientists such as Dr Eville Gorham, Dr Svante Odén and Dr Harold Harvey. Scientific and public reaction to their work was generally negative.

Over the past two decades, the scientific understanding of the problem has dramatically improved. As this information became understood by the public, support for the control of atmospheric pollution increased to the point where virtually all industrialised countries are now implementing sulphur dioxide control programmes.

The industrial reaction to environmental control has become much more positive over the past few years with many industrial sectors now being equal partners in discussions of solutions to environmental problems. While pollution control programmes cost considerable amounts of money, it has been shown that these costs are manageable and that clean environments are conducive to economic development.

Opinion polls have shown that the public in Canada and the U.K., for example, places high priority on the need for environmental protection.

The positive industrial attitude, the increased public concern and the need to understand the science of complex environmental issues, in order to design the best possible control programme, together necessitate the involvement of environmental scientists in public debates if rational decisions are to be taken.

The natural distribution of Sitka spruce is examined in relation to the species' role in British forestry. Particular attention is therefore given to a description of habitats on the Queen Charlotte Islands, and also on the adjacent mainland of British Columbia where Sitka spruce is sympatric with white spruce (Picea glauca) and hybridisation occurs. Examples of genetic variation are given and it is suggested that a knowledge of the genecologv of the species in its natural habitat would help to elucidate its full ecological and genetic potential in Britain.

In two earlier publications the author has suggested a theory of genetically determined asymmetries. Inherited asymmetry may be of two types. Many characters are unilateral (e.g. the aortic arch or the tricuspid valve of the human heart) or in some other way placed asymmetrically (e.g. the differentiation of organs along the cephalad-caudad axis of the body). The orientation of such gross asymmetries is in general irreversible. The author has pointed out that the study of uniovular twins which exhibit mirror-image similarities draws attention to a smaller class of reversible asymmetries. While an asymmetrical disposition of such a character is transmitted, its orientation is not fixed in the process of transmission. Thus a character may show itself on the left side in one generation or in one individual of a litter, and on the right side in another generation or in a litter mate. The extreme types of variation between which many transitional forms may be found are:

(a) From left to right, or vice versa.

(b) From caudad to cephalad extremity, or vice versa.

(c) From dorsal to ventral surface, or vice versa.

Tradescantia pollen grains are excellent material for the analysis of X-ray effects. The influence of radiation on cell development, nuclear differentiation, as well as on chromosome structure can be studied. Extensive quantitative analyses, which primarily concern the mechanism of chromosome breaks and reunions induced by radiation, have already been made (Riley, 1936; Sax, 1938, 1940, 1941; Fabergé, 1940). The present paper contains data which show the effects of radiation on cell development, chromosome behaviour, nuclear differentiation, and pollen germination. It is expected that the data obtained will throw some light on the intricate mechanism present within the cell and show that the governing centre of this mechanism is the nucleus.

Young Sitka spruce trees grow slowly, compared with poplar for instance, because of lower photosynthetic rates and slower rates of leaf area production. On the other hand, the canopies of Sitka spruce stands have structural and photosynthetic properties which make them very productive. Both the slow growth of young trees, and the high productivities of closed stands, can be attributed to the needle habit.

The stomodæum appears as an ectodermal invagination. The oesophagus develops from an outgrowth (posterior) and the radular sac from a ventral evagination of the floor of the stomodæum. The basal epithelium of the radular sac secretes the radular membrane and the teeth, while the dorsal epithelium contributes towards the hardening of the teeth. The subradular cavity is formed from a depression of the floor and the salivary glands from two evaginations of the roof of the stomodæum. The buccal cartilage is mesodermal, while the jaw is ectodermal. The blastopore closes. Only the posterior part of the archenteron takes part in the formation of the gut, from which the crop, stomach and the digestive gland develop. The anterior chamber of the crop develops from a diverticulum of the archenteron. The anterior and posterior lobes of the digestive gland arise from the anterior part of the primitive stomach dorsally and on the left side respectively; the posterior chamber of the crop from the anteroventral region of the primitive stomach, and the stomach from the posterior right side of its floor. The hind gut appears by the arrangement of cells proliferated from that part of the archenteron where blastopore closes. It opens anterodorsally into the primitive stomach in a 2½ mm. embryo; the anus appears in a late embryo about 12 days old.

Weedy nature and critical taxonomic status of widespread autogamous annual brome-grasses combine to make assessments of their native phytogeographical areas uncertain or impossible. Suggested criteria for determining native status are reviewed. Some species found in SW Asia occur also in Europe. Some others are so far known only in Europe and may either be native there or introduced from SW Asia. These possibilities are considered by applying native status criteria to 10 principal exemplar species and 4 subspecies. On the basis of known distributions, these criteria suggest that: (i) some species are not native in any primary habitats, and perhaps never have been; (ii) though SW Asia seems to be the centre from which the current adaptive radiation of Bromus L. annuals began, not all its brome-grass flora is native, and some of its probable native species are known only as introduced plants in Europe i.e. are undiscovered in SW Asia. It is urged that our imperfect knowledge of distributions in this critical group be remedied by careful analysis of the brome-grass flora of primary habitats in SW Asia.

Data from the Clyde demersal fishery during the period 1960 to 1984 are presented. Annual landings of demersal species at Chde ports in recent years have ranged from 4000 to 10,000 tonnes, with a first sale value of £2–5 million. In the 1960s the fishery was undertaken mainly by seine-net vessels, but the present fleet consists largely of dual-purpose light/Nephrops trawlers. The demersal fishery is seasonal and during the winter and spring there is an influx of ‘stranger’ vessels. Five species (cod, whiting, saithe, hake and haddock) make up more than 80% of the demersal landings from the Clyde. The landings of saithe have fluctuated very considerably during the period under review. Other relatively important species are dogfish, plaice, skate and ray and angler fish. In general the Clyde fishery represents only a small proportion of the total Scottish landings but in recent years landings of hake from the Clyde grounds have averaged approximately 40% of the Scottish hake total. The Clyde demersal fishery depends to a large extent on young fish and both the total annual landings and the relative importance of the principal species fluctuate from year to year in response to variations in the strength of the recruiting year classes. The catch rates of the principal species vary greatly throughout the year. Although there is no conclusive evidence that the Clyde populations are self-contained, all the major species are known to spawn within or close to the area and tagging experiments have suggested that there may not be much mixing between Clyde fish and those from surrounding areas. This may in part, however, reflect the fact that fishing intensity within the Clyde is high and fish are recaptured before they have had time to leave the area. For management purposes, the Clyde demersal stocks are included in ICES Sub-area VI.

While the role of oestrogens in breast cancer has been recognised for over a century, until recently our understanding of the mechanism by which they act has been limited, despite zealous efforts on the part of many investigators to seek for differences in oestrogen levels or metabolism in cancer patients. Since the initiation of breast cancer occurs many years before the detection of overt disease, it seems reasonable to suggest that these earlier studies may have been carried out at the wrong stage of the disease. Using a time invariant radiometric procedure, we have established that of the three principal sites of oestrogen metabolism at C-2, C-16α, and C-17, only C-16α hydroxylation is elevated in women with breast cancer. Further studies in women at high risk for breast cancer for familial reasons showed that they have an elevated rate of 16α-hydroxylation. Parallel studies in mice with high and low rates of spontaneous mammary tumour formation show a close parallelism between the extent of 16α-hydroxylation and tumour incidence. Studies of 16α-hydroxyoestrone, the product of 16α-hydroxylation, have demonstrated that it is a unique oestrogen, capable of binding irreversibly to the oestrogen receptor and permanently activating it. Studies on the effects of diet and drugs on the extent of C-2 and C-16α hydroxylation have shown that while the former reaction is easily increased or decreased, the latter is refractory to treatment and behaves like a constitutive enzyme. Thus, treatment with cimetidine, obesity, or high fat diets decrease the extent of C-2 hydroxylation, while high protein diets, hyperthyroidism, smoking, or dioxins increase C-2 hydroxylation. In contrast, 16α-hydroxylation is essentially unchanged in any of these conditions.

A link between increased C-2 hydroxylation and decreased levels of breast and endometrial cancer is suggested by epidemiological studies in smokers. Conversely, decreases in this reaction as in obesity are associated with increased risk for these tumours. The aim of these studies is to develop a safe prophylactic regimen which will increase C-2 hydroxylation, resulting in a decrease in active oestrogen and a lower tumour incidence.

The topographic and sedimentary characteristics of the Voe are briefly described and used to define the distribution of epifaunal and macro- and meio-infaunal communities throughout the Voe. The structural complexity of the communities, their interdependence on one or a group of dominant species, and their trophic relationships are emphasized. Changing distributions with depth and in time are examined in detail, particularly in relation to the intermittently eutrophic conditions occurring in the inner basin of the Voe.

Uptake of oestrogens into breast tissue and their subsequent metabolism can be studied by infusing radio-labelled steroids into volunteer patients. Such studies show that oestradiol is preferentially accumulated in breast tumours, oestradiol concentrations exceeding those of oestrone. This contrasts with plasma, in which oestrone concentrations in postmenopausal women are greater than those of the oestradiol. This observation suggests that tissue factors can modulate local oestrogen metabolism, and thus local steroid concentrations.

We have studied the local production of oestrogens from androgen, and also the interconversion of the major oestrogens, oestrone and oestradiol. Using isotopic techniques, it is possible to calculate the proportion of endogenous oestrogen produced from androgen, as opposed to uptake from the circulation. These studies suggest that a very variable proportion of tissue oestrogen derives from endogenous synthesis. After administration of aromatase inhibitors, aromatase activity is substantially inhibited, both in vivo and in vitro.

Relative oestrogen concentrations are determined in part by the activity of oestradiol dehydrogenase. In breast tissue, dehydrogenase activity is present and this is modified by various factors, including androgens. In addition, we have demonstrated that normal, benign and malignant breast tissues produce factors which can modulate both growth and dehydrogenase activity of cancer cells in vitro.

We conclude that breast tissue is a site of synthesis of oestrogens, and that a number of factors can affect their local concentration. Tumour cells produce growth factors which can influence steroid metabolism, and may thus be able to enhance favourably their own endocrine environment.

The ecological role of native willows is described in terms of the diverse structure of the species involved, the wide range of plant communities they form and the large numbers of invertebrates associated with them. The conservation importance of the genus Salix is discussed along with comments on the necessary management to retain willow habitats.

Marcet reported in 1822 that sea salt contained lime, and several investigators confirmed its presence in sea water in the 1830s. Darondeau found dissolved CO2 in sea water in 1838, and von Bibra in 1851 considered sea water to be slightly alkaline. Tornöe in 1880 pointed out that this condition required part of the CO2 to be bound chemically, and Hamberg applied the mass action law to the CO2-system in sea water in 1885. For nearly 50 years, however, despite the development of the concepts of pH and activity, attempts to apply the law in detail failed, first because the behaviour of H2CO3 and HCO3− as weak acids is strikingly different in pure water, sea water or NaCl solutions, and secondly because the presence and role of another weak acid, boric acid, was not recognised fully until 1933. Investigators often attributed their failures to some mysterious ability of the sea to disregard or evade the laws of physical chemistry. Buch in 1933 and 1938 finally laid this hobgoblin to rest, and his results are still accepted with only minor modifications.

In previous contributions the writer has described the structure and behaviour of the mitochondria and Golgi material of the egg of the mouse (Gresson, 1933, 1938 and 1940 b), and more recently has traced the cytoplasmic inclusions through the stages of maturation, fertilisation and the first cleavage division (Gresson, 1941). As the result of observations on the sperm middle-piece it is claimed that the mitochondria of the sheath are liberated into the ooplasm of the fertilised egg, and are shared out between the first two blastomeres; and further, that a Golgi element is present in the middle-piece, and that this breaks up and its products are distributed through the cytoplasm of the fertilised ovum (Gresson, 1940a, and 1941).

Experiments have shown that Sitka spruce on poor soils requires relatively frequent applications of fertiliser, phosphorus being most commonly required, other deficiencies in decreasing frequency being potassium, nitrogen and, very rarely, copper. Recent evidence suggests that growth responses to fertilisers are commonest while stands are young and the green canopy is being established. Spruce has a heavy crown and in consequence nutrient demands are high prior to canopy closure. Thereafter, the annual production of foliage by spruce is no greater than that of other species of comparable growth rate and by this stage the establishment of cycles within the tree and through the litter layer enable efficient re-use of nutrients and hence the demands placed upon the soil fall dramatically.

A 3-year survey of wild fish in Loch Awe and the surrounding watershed has shown a restricted distribution and low prevalence of infection with infectious pancreatic necrosis virus. No signs of clinical disease were observed in infected fish. The restricted distribution close to a rainbow trout farm is consistent with the virus originating from this farm, where virus infected stocks have been found each year since 1971. The continuing low prevalence is also consistent with virus in wild fish resulting from the spread of infection from the farm. If infection is spreading between wild fish, it is slow within the time scale of the survey. The possible mechanisms of transmission of infection from the farm to wild fish are discussed.

Life histories and production of the five common species of Tanypodinae (Pentaneura monilis, Procladius simplicistilus, P. crassinervis, P. choreus and Psilotanypus rufovittatus) in the mud at Loch Leven were measured from March 1971 to March 1972. The methods used to identify each species of larva are described. All were univoltine except Pentaneura monilis which had two generations per year, but the seasonal patterns of the life cycles were different. The average density of third and fourth instar Tanypodinae was 3100/m2 and densities of individual species exceeded 2500/m2 for short periods in Procladius crassinervis and P. choreus. Net annual dry weight production by this subfamily was 2·6 g/m2(57 kJ/m2), with individual species ranging from 1·1 g/m2 (P. crassinervis) to 0·16 g/m2 (Pentaneura monilis). These results are discussed briefly and compared with production estimates for other zoobenthos.

During the winter of 1937–38 it became necessary to obtain the maximum number of offspring from a certain pen mating for the purposes of an experiment unconnected with the present report. Accordingly all suitable eggs were incubated, and since chicks were required all the year round the data which accumulated related to periods extending beyond the normal hatching season. Not long after the beginning of the project strikingly consistent differences between the records of the individual females became apparent, and interest in this phenomenon led to the decision to incubate every intact egg from the pen, irrespective of any normally undesirable characteristics of shell texture or shape. This was done for two years (1938–39), and provided the main data for the study of fertility and embryonic mortality reported here.

Viral erythrocytic necrosis (VEN) in fish is prevalent in a wide variety offish species. It has been detected in both wild and captive fish populations. The infection prevalence in wild populations of some fish species is correlated inversely with the age of the fish. VEN is characterised by cytoplasmic inclusions in circulating erythrocytes of infected fish; nuclear necrosis of erythrocytes may also be evident by light microscopy. The stage and degree of infection affect the type of cytology seen in VEN infections of different fish species. By electron microscopy, infected erythrocytes show spherical virions within the cytoplasm and the virion size is characteristic of the host erythrocytes infected. To date, knowledge of VEN viruses in fish is restricted to virus morphology and propagation in vivo, although preliminary studies have indicated the type of blood parameters which VEN can affect. No such virus has been fully isolated and characterised and all of Koch's postulates have not been fulfilled.