The common strain and six specialised strains of Phytophthora infestans have been employed in testing potato varieties and seedling progenies bred from the wild species S. demissum for resistance to the disease. Resistance, due to the hypersensitive condition of the protoplasm, is manifested in the presence of major genes, and four such genes have been identified, viz. R1, R2, R3 and R4. Each gene induces in the plant a hypersensitive response to infection with the common strain and with a particular group of specialised strains of the parasite. The genes are inherited independently in simple Mendelian fashion, but in the segregations three different types of deviations from standard disomic ratios occur due to (a) unpaired chromosomes, (b) incompatibility factors, and (c) partial autosyndesis. A series of minor genes modify the phenotypic expression of the major gene system and so differentiate grades of hypersensitivity or of susceptibility as the case may be.

The common strain of P. infestans appears to be a population persisting at an equilibrium determined by host range and environmental conditions. Mutations frequently occur, but new forms survive only when host genotypes, to which they are specially adapted, are available.

Intravenous injection of posterior lobe pituitary extracts into spinal or anæsthetised mammals has several effects. One is to elevate blood pressure. Two animal preparations are commonly used for the biological assay of this activity. Most American workers seem to favour a dog deeply anæsthetised with chloretone or chloralose. 10 per cent, accuracy is claimed. We have no experience of this preparation. There have been very few tracings published and those that we have seen do not inspire confidence. This apart, a method employing dogs is unlikely to find favour in this country because of the difficulty of obtaining, feeding, and housing suitable animals. Most workers in this country use the spinal cat. As originally described by Dale and Laidlaw (1912), the method employing this preparation was insensitive and open to grave errors. Hogben et al. (1924), after intensive study, showed that it could be sensitive, reliable, and susceptible of good discrimination. The Hogben procedure has been generally adopted.

Analyses of winter and summer vertical migrations of Meganyctiphanes norvegica are given and the differences in behaviour pointed out. A vertical layering of size classes, larger specimens occurring deeper than smaller ones, is shown to exist during the day and night.

Four potential methods of feeding were found. The inter-relationships between vertical migration, feeding method used, and type of food eaten are discussed.

The relationship of carapace length to total length was found to depend on the state of maturity of M. norvegica.

M. norvegica matures at the age of 1 year, transference of the spermatophores taking place in January-February, the eggs being laid in March-April. The larvae take 2–3 months to reach adolescence and little growth in size takes place in the winter when the gonads are maturing. An age of 3 years may be attained but most only survive 1½—2 years.

The distribution within the Clyde Sea throughout the year is described. Most of the population were found to move to the North-east Arran Area for egg-laying.

A 24-hr. and annual periodicity of luminescence is described and correlated with the period of swarming of this species prior to spermatophore transference.

The study began in 1978 at Glenbranter Forest, Argyll. Use of habitat by red and roe deer was measured from the accumulation of pellet groups and from observations. Approximately 2000 trees less than 9 years old and 6000 older ones were monitored for damage and response.

Habitats in areas dominated by heather in or close to the forest were the most occupied by both species and pole-stage crops the least. However, most dung was found on the extensive areas of recently planted ground. Roe deer were relatively more abundant than red deer in stands of 9 to 15 year-old trees.

In summer, red deer ate mainly grasses and roe mainly forbs. In winter, these preferences remained, but Calluna became more important to both.

Browsing on leaders was heaviest in winter and May–June. Approximately 50% of leaders on trees less than 6 years old were browsed annually. Most trees regained leaders within 12 months, many becoming multi-stemmed. Of the trees. 1% were bark-stripped per annum. In older stands the smaller trees were most damaged, in younger stands the larger trees.

The studies on the epidemiology of yellow fever which have been carried out in Africa in the period 1925–1966 are presented in narrative form.

The original isolation of the virus is described, leading on to the survey work which showed that the infection is widespread in tropical Africa and that monkeys are very important hosts—perhaps the definitive mammalian hosts—of the virus. The discoveries of a monkey-to-man cycle in which the classical vector mosquito, Aedes aegypti, is replaced by A. simpsoni and of a monkey-to-monkey cycle, in which A. africanus is the vector, are described.

Recent epidemics are discussed, particularly that in Ethiopia, where there were about 200,000 cases, with 30,000 deaths, in the period 1960–62 and where the principal vector in the man-to-man cycle was A. simpsoni.

Work on groups of animals other than monkeys is reviewed, with particular reference to studies on the lemuroid Primates of the genus Galago, which are believed to be natural hosts of the virus. It is concluded that there are still many unknown facets in the epidemiology.

Ship and satellite studies along the shelf edge to the south west of the British Isles have demonstrated the persistence of relatively high standing crops of phytoplankton during the summer months in a region of strong tidal currents and internal wave activity. Off southwest Ireland there is also evidence that salinity stratification has a significant influence on phytoplankton growth, at least during the spring months. Coastal Zone Color Scanner (CZCS) images for the region to the north and west of Scotland indicate that phytoplankton distributions close to the shelf edge are influenced by mesoscale eddies in the Rockall Trough impinging on the upper slope. Coccolithophore blooms are frequent, and changes in their surface distributions are good indicators of water motion.

According to Grollman (1936), there is no evidence for an intimate relation between the gonads and the adrenal proper, i.e. the cortex apart from the “fœtal zone” (Grollman, 1942). Recent papers, however (Bourne and Zuckerman, 1940 a, 1940 b; Schilling and Laqueur, 1941; Selye and Albert, 1942; Selye, Rowley, and Hall, 1943; Sarason, 1943, and others), confirm the opposite view (Kolmer, 1912; Korenchevsky, Dennison, and Simpson, 1935). The results, especially those concerning the action of gonadal substances on the adrenal cortex, vary as between different authors and according to the species of experimental animal used. Grollman (1936), for example, states that the cortex is not influenced by œstrogen. Allen and Bern (1942), however, and Golla and Reiss (1942) report a change in the cortex associated with an increase of adrenal weight. The former authors found an increase in lipoid-containing vacuoles in guinea-pigs treated with stilbœstrol; the latter, on the other hand, observed a lipoid decrease in rats treated with œstrone. Comparison of these results with others which they obtained with hypophysectomized rats even led Golla and Reiss to postulate the existence of two corticotrophic principles in the hypophysis: one controlling the distribution of lipoid in the cortex and the other the adrenal weight.

Perennial indendent gametophytes of Hymenophyllaceae, Vittariaceae and Grammitidaceae are a well-known phenomenon in the eastern United States. Their persistence is attributed to the ability of gametophytes of these fern families to reproduce themselves vegetatively via gemmae. This paper reviews the biology of independent gametophytes of these families as they exist in the eastern United States and presents new evidence from enzyme electrophoresis regarding their identity and origin.

South of St Kilda, Atlantic water reaches the edge of the Continental Shelf west of the Hebrides from the eastern side of the Rockall Channel, whereas the main north-east going current from the western side of the channel probably lies close to the shelf-edge to the north of St Kilda. On the shelf, Atlantic water mixes with Clyde and Irish Sea water to the south-west of the Small Isles, and the mixed water so formed diverges to flow partly northward through the Little Minch and partly southward to Barra Head, then northward along the western coasts of the Outer Hebrides. On the outer shelf, dense winter-formed bottom water persists into the autumn, implying that advection is weak in this region in summer.

Data of temperature and salinity are sparse around the Outer Hebrides. Annual temperature cycles at depth on the shelf can be explained in terms of the cycle of wind mixing. A non-divergent Continental Shelf wave gives rise to strong diurnal components in the tidal streams upon the outer shelf and in the Sound of Harris, but causes no perceptible disturbance to the semi-diurnal rise and fall.

The location and major characteristics of Loch Leven and land use of its catchment are briefly described. The water level was lowered in 1830 affecting migrant fish. Many changes have taken place in the fauna and flora in the present century with serious depletions to the macrophytes, Odonata and Ephemeroptera. The loch is of international importance for waterfowl and was made into a National Nature Reserve in 1964. An IBP project was started in 1966 to measure production and production processes in the food chain to fish and diving duck. Energy and nutrient input, production of phytoplankton, chironomids and the larger trout and perch have been measured for the whole loch. Many other related studies have been carried out. The numbers of several groups have been shown to fluctuate greatly from year to year, as have the principal components of phytoplankton, zooplankton and zoobenthos.

The distribution and production of submerged macrophytes in Loch Leven has been investigated using drag-rake surveys and biomass measurements. Survey data suggest that changes in the species diversity of the loch have occurred since the earlier records. There appears to have been a decline in some species with an increase in others.

In general there has been an overall loss in species diversity which may be correlated with the increasingly eutrophic status of Loch Leven. At present the macrophyte flora is dominated by a few species, notably Potamogeton filiformis, Zannichellia palustris, Nitella opaca and algal periphyton, with declining, though still significant amounts of Chora aspera. It is probable that the species diversity is in the process of adjusting to the eutrophic status of the loch and that P. filiformis in particular is in an expanding condition.

The distribution and ecological characteristics of the thorn-cushion formations (Tragacanthic vegetation) in the western part of SW Asia are discussed. The typical structure of this formation is illustrated by 2 examples from the mountains of the Antilebanon. These show a clear zonation in relation to the growth form. This, and the available micro-climatological data, show that thorn-cushions reach their ecological optimum on windswept slopes and hill tops. This growth form is obviously an adaptation for sites exposed to strong winds. Taxa with this growth form have a competitive advantage in such habitats.

The halophytic communities of Iran and Afghanistan are rich in species compared with similar communities in S Europe or in N America. Ionic composition and the ion concentrations in the respective habitats characterise the main phytochemical types which develop. Such chemotypes or physiotypes of halophytes are partly correlated with conventional taxonomic units. The various types of halophytes from Iran and Afghanistan were compared and some eco-physiological characteristics are presented. The differences between “stem-halosucculents”, “leaf-halosucculents”, “recreting halophytes”, and types of ‘salt-avoiders” (“pseudohalophytes” and “non-halophytes” or “glycophytes”) are stressed. The ecological implications of the characteristics of these different halophytes, which lead to a typical halo-catena, are discussed.

The control of stomatal aperture by intensity of light, under normal conditions of water-relations of surrounding cells, has apparently been established by Nutman (1937) for coffee leaves. This control results in the closing of stomatal pores both with too little and with too much illumination. Since photosynthesis in the guard-cells is not known to decrease with increase in light intensity, up to the limit of full sunshine, some other factor or factors are suggested as coming into action.

Investigations, in the Department of Botany, Queen's University, Belfast, by three research students have progressively elucidated some of the factors concerned.

The classical view that, of the two known types of nucleic acid, desoxyribonucleic acid (thymonucleic acid) is characteristic of animal tissues and ribonucleic acid (pentose nucleic acid) of plant tissues, was established by the work of Kossel and others and upheld as a fundamental generalisation by Jones (1920). This view, which was current for over thirty years, has had to be abandoned in the light of more recent evidence. Not only has desoxyribonucleic acid been found in plant tissues, but ribonucleic acid has been isolated from the pancreas (Jorpes, 1928, 1934) and has been shown to be widespread in animal tissues (Davidson and Waymouth, 1943, 1944 a, b). Ribonucleic acid has been isolated, also, from liver tissue, in which it is present in much larger amounts than is desoxyribonucleic acid (Davidson and Waymouth, 1944 c).

The Galileo satellite during its recent passes close to the Earth recorded a planet with an unusual red-absorbing pigment, a poisonous atmosphere, simultaneously rich in oxygen and in methane, with strong, modulated, narrow-band, radio emissions in the MHz frequencies (Sagan et al. 1993). To an observer visiting the solar system, these features; the photo-oxidisable pigment chlorophyll, abundant atmospheric oxygen, the existence of reducing conditions and intelligent life might well appear self-contradictory. While intelligent life is a recent event, the presence of other forms of life based on photosynthesis and survival under both oxygen-rich atmospheres and reducing conditions go back to the earliest times (Table 1). Life on Earth has evolved over nearly 4 G years under atmospheric environments ranging from anoxia, to hypoxia, to hyperoxia (relative to the present day), and not always in that sequence.

Species of Isoetes in northeastern North America may have evolved through hybridisation and allopolyploidy. Evidence for natural hybridisation was obtained from overlapping distribution patterns, abortive and polymorphic spore formation, chromosome numbers ranging from diploid to decaploid, and additive enzyme electrophoresis profiles. The ease with which hybrids form in culture supports the hypothesis that natural hybrids occur and that hybridisation could be involved in the evolution of new species.

Drosophila melanogaster larvæ when cultured aseptically on a synthetic diet require exogenous ribose nucleic acid (RNA) for normal growth even though they can synthesize their own endogenous RNA from simple precursors. The optimum dietary supply lies between 0.4 and 0.7 per cent RNA. Individual bases, nucleosides and nucleotides which make up RNA cannot substitute for the whole polynucleotide, but adenine, adenosine, adenylic acid, guanosine and guanylic acid are used and stimulate growth to varying degrees. The pyrimidines and their nucleosides and nucleotides are not used when fed singly.

It is shown that the de novo synthesis of purines may be more difficult than that of pyrimidines, and that if a source of purines is supplied (as adenylic acid), then the nucleosides and nucleotides of both cytosine and uracil are utilized by the larvæ, whereas the free bases are not. Cytidylic and uridylic acids seem to be interchangeable, and together with an adequate supply of adenylic acid give as good growth as RNA. Orotic acid and 2—6-diaminopurine are not used by the larvæ under the conditions described, but hypoxanthine and inosine are: xanthine and xanthosine can also be shown to have an effect on growth.

Dose-response curves were determined for adenylic, guanylic, cytidylic and uridylic acids under conditions which allow the determination of the optimal supplies of each. These are found to be about 0.110, 0.080, 0.025 and 0.025 per cent, respectively. The requirement of RNA is therefore primarily a requirement of adenylic acid, since more than enough of the other nucleotides should be available when the supply of RNA is optimal. The optimal supply of adenine corresponds almost exactly with the optimal supply of adenylic acid, though a somewhat delayed larval development may be a result of energy utilization in the base-nucleoside-nucleotide conversion.

These results are discussed in the light of our knowledge of purine and pyrimidine utilization in other multicellular organisms, particularly the rat, and possible applications of the findings are considered.

Salix has many physiological features in common with other deciduous woody plants, e.g. C3 photosynthesis, occurrence of latitudinal photoperiodic ecotypes, and organic N (no ) flux to the shoot in the xylem. Special points about the physiology of Salix spp. which may have impact on their ecology and economic uses include: (i) relatively high (for woody plants) light-saturated rate of photosynthesis on a leaf area or leaf dry weight basis, (ii) sex differences in water (transpiration) costs of growth, (iii) very limited seed longevity and a wide range of temperature and light conditions permitting germination, and (iv) ready rooting and establishment of naturally or artificially detached twigs and branches. Areas in which work on Salix has been especially influential for the development of plant physiology include: (i) the analysis of phloem functioning using aphids, (ii) the role of photoinhibition under natural conditions, and (iii) the realisation that the woody habit need not constrain the achieved activity of enzymes and hence N-based metabolic rates.

Diameter frequency distributions (dfds) of 197 tree species in Korup National Park and 118 tree species in Douala–Edea Forest Reserve (based on c. 41 000 and 25 000 trees ≥ 30 cm gbh in 135 and 104 plots along four transects at each site, respectively) were individually classified into four groups of species according to their maximum diameters (≥99% trees <50, <70 and <90cm dbh, and > 1% ≥90cm dbh), and separated into two abundance classes (n≥50 and n = 20–49 (or 15–49). A fifth group, from those species in 3 and 4, was defined by a relative lack of small stems and given detailed attention. Dfds were evaluated for all species together on a transect and site basis, and compared for individual species across transects, and between sites for those group 5 species in common.

Analysis focussed on three large ectomycorrhizal species in groups 3 and 4, Microberlinia bisulcata, Tetraberlinia bifoliolata and T. moreliana (Caesalpiniaceae), which were restricted to, and dominated, the forest on the nutrient-poor soils of transect P at Korup. M. bisulcata, the most abundant, was markedly group 5 in character, with very few small trees, whilst the Tetraberlinia species had strong replacement potential. Although there were 27 species (42% of groups 3 & 4) at Korup and 19 (48%) at Douala–Edea in group 5, M. bisulcata was unique in its combination of large size, dfd, mycorrhizal habit, spatial distribution and soil association. The potential replacement of this species was contrasted also with a non-ectomycorrhizal caesalp with similar dfd that occurred on nutrient-richer soils, Erythrophleum ivorense.

Knowledge of the Caesalpiniaceae-rich la forêt biafriéene of Letouzey (which includes Korup and Douala–Edea) is reviewed, and the distribution, ecology and regeneration of the caesalps discussed. Structure and inferred dynamics of the forest at Korup are discussed with special regard to the ectomycorrhizal species.