bluuebunny/crossref_metadata_2025 huggingface dataset:
THE APPLIED BIOLOGIST, THE CHILD, AND SOCIETY
Authors: KRAMER L.M.J.
Published: February 2008

Consideration of the characteristics of past and current applied biology reveals its fundamentally ecological nature, and also indicates the potent influence of the applied biologist upon society. It is urged that in order to impress influence upon pupils biological education should be based mainly upon field studies, rather than upon predominantly evolutionary, morphological and physiological studies. The nature of past and existing school biology strongly reinforces the abovel conclusion.

The results of attempts to find and evaluate evidence of the social influences of past and present biological education are presented, both in relation to the whole population, as well as to particular aspects, like food poisoning, the press, and the education of Civil Servants and Members of Parliment.

The potentialities of a Sixth Form biology resting chiefly upon field study are discussed not only as a means of developing an outlook valuable to‐day, but also of treating suitably the pre‐university education of future applied biologists.
NEMATOLOGY IN RETROSPECT AND PROSPECT
Authors: PETERS B. G.
Published: February 2008

The first small nematodes to be described, free‐living in the seventeenth century and plant‐parasitic in the eighteenth, are identifiable only from their peculiar habitats; taxonomy came relatively late in nematology because adequate optical equipment was a prerequisite. In the study of the free‐living and the plant‐parasitic species, the development of two readily‐presented aspects of taxonomy, figure drawing and mensuration (each showing oscillation between paucity and excess of detail), is traced in the work of five founders, all of whom were living in 1904: Bastian, Bütschli, de Man, Cobb and Goodey. Possible future developments in the identification of species and strains, the investigation of host‐parasite relationships, and the training of nematologists are briefly discussed.
THE SEASONAL RESPONSE OF THE POTATO‐ROOT EELWORM HETERODERA ROSTOCHIENSIS WOLLEN‐WEBER: EMERGENCE OF LARVAE THROUGHOUT THE YEAR FROM CYSTS EXPOSED TO DIFFERENT TEMPERATURE CYCLES
Authors: ELLENBY C.
Published: February 2008

Air dried cysts collected in 1945 were maintained under five different conditions. One lot was maintained at room temperature, and other lots at 23h° C. and at about 5° C; of the remaining two lots, one spent 6 months of each year at 23° C. and 6 months at 5° C, while the other was subjected to the opposite treatment. Hatching trials were carried out at 1‐ or 2‐month intervals, beginning about a year after the establishment of the regime, and were continued until 1949. Throughout, cysts were stimulated with solutions of the same sample of concentrated hatching solid.

Larval emergence was high throughout in cysts from all treatments. Although there was considerable variation in larval emergence there is no evidence of any dormancy period. Significant differences in the level of emergence from cysts on the different treatments are demonstrated, the cysts stored at room temperature showing the highest levels of larval emergence. It is also shown that there are significant differences in the responses in the different hatching trials; however, there is no suggestion that these are of a seasonal nature.

Other experiments suggest that many of the eggs in apparently mature cysts do not reach maturity for some months.
THE PERMEABILITY TO THE HATCHING FACTOR OF THE CYST WALL OF THE POTATO‐ROOT EELWORM, HETERODERA ROSTOCHIENSIS WOLLENWEBER
Authors: ELLENBY C.
Published: February 2008

Experiments are described in which a particle of concentrated hatching factor is separated by cyst wall from eelworm eggs. Comparison of the hatching of these and control eggs showed that the cyst wall is permeable to the hatching stimulant. The experiments also demonstrated that the cyst wall is permeable to dissolved air.
A COMPARATIVE STUDY OF OPHIOBOLUS GRAMINIS AND FUSARIUM CULMORUM IN SAPROPHYTIC COLONIZATION OF WHEAT STRAW
Authors: LUCAS R. L.
Published: February 2008

The competitive saprophytic ability of Ophiobolus graminis has been compared with that of Fusarium cultnorum. Test pieces of wheat straw were buried in maize‐meal‐sand inoculum mixed in various proportions with unsterilized soil, according to the technique already described by Butler (1953). Some possible sources of variation in the results obtained by this technique have been investigated. Saprophytic colonization of the straw tissues by Ophiobolus graminis appeared to decline as invasion progressed from the outer to the inner tissues, presumably owing to continued competition with other saprophytes. An experiment using as inoculum the stubble of plants naturally infected by O. graminis suggests that saprophytic colonization of wheat straw by the take‐all fungus can occur only to a negligible extent in the field.
PARTICLE SIZE OF INSECTICIDAL SUSPENSIONS AND THEIR CONTACT TOXICITY: V. EFFECT OF PHYSICAL PROPERTIES ON TOXICITY OF COMPOUNDS IN THE DDT GROUP
Authors: McINTOSH A. H.
Published: February 2008

With each of nine DDT analogues, two types of simple aqueous suspension were made, one containing crystals of uniform size, and the other containing colloidal particles. The toxicities of each pair of suspensions were compared by a dipping method on adult Oryzaephilus surinamensis L., kept at n° C. for 24 hr. after treatment. The colloid was always as toxic as the crystals, or more toxic. This difference in toxicity varied from one analogue to another. It was related to the physical properties of the analogue in the following way.

Dipping applies poison to the insects; the amounts retained could usually be found by extraction and microanalysis. Retention of poison from colloidal suspension was about the same for each analogue; but crystals were retained either more or less efficiently than colloid, depending on their size and shape. Poorest retention was found with plate‐like crystals of about 25μ.

The true ratio of toxicities for each analogue (colloid : crystals) was found by correcting the observed ratio for differences in retention; but even then there were still big differences amongst the ratios given by the different analogues.

The true ratio was taken as a measure of the difference in speed of action between the two forms of poison. If the compound could kill O. surinamensis by fumigant action alone, the true ratio was very small. Otherwise, it seemed to depend on two physical properties related to the process of solution of poison in the wax of the insect cuticle. They were both measured in in vitro tests. The film made by evaporating a drop of colloidal suspension on glass is at first globular, but it may sooner or later crystallize. The film made by evaporating a drop of a suspension of crystals can be dissolved in olive oil. If the film of crystals brought about saturation of olive oil slowly and if, in addition, the deposit from colloid crystallized slowly, the true ratio was large. Unless the analogue had both of these properties, the true ratio was small. If the analogue had one or other of the properties, the true ratio could be increased either by increasing the crystal size or by decreasing the rate of crystallization.

Physical properties of this sort may often affect the results of tests of insecticides, and should be taken into account when the toxicities of different compounds are compared.

There seems to be no relation between lipoid‐solubility and toxicity of compounds in the DDT group. Rate of solution is probably more important.
THE SYSTEMIC PROPERTIES OF DIETHYL‐S‐z‐ (ETHYLTHIOETHYL) PHOSPHOROTHIOLATE (DEMETON‐S) WITH REFERENCE TO THE CONTAMINATION OF NECTAR
Authors: Thomas W. D. E. , JONES G. D. GLYNNE
Published: February 2008

The fate of diethyl 5‐2‐(ethylthioethyl) phosphorothiolate (demeton‐S) in white mustard (Brassica alba), borage (Borago officinalis) and field beans (Viciafaba) has been followed over several weeks using the radioactive tracer technique. Radio‐assay of nectar samples from flowers which opened a few days after spraying showed that no unchanged demeton‐S, but that small amounts of degradation products were present. The highest value for total radioactivity found in the nectar corresponded to 2–7 p.p.m. expressed as demeton‐S.

Radioassay of treated leaves and new growth after spraying confirmed that demeton‐S is rapidly con, erted in the plant into two primary degradation products extractable by chloroform. Further breakdotvn is more rapid in new growth and appreciable quantities of the two primary products believed to be biologically active are retained by the treated leaves.
THE INFLUENCE OF DISSOLVED‐OXYGEN CONCENTRATION ON THE TOXICITY OF UN‐IONIZED AMMONIA TO RAINBOW TROUT (SALMO GAIRDNERII RICHARDSON)
Authors: DOWNING KATHLEEN M. , MERKENS J. C.
Published: February 2008

Periods of survival of rainbow trout in concentrations of un‐ionized ammonia in the range 0.86‐1.96 parts per million of nitrogen increased as the concentration of dissolved oxygen was raised from 1–5 to 8‐5 p.p.m.

At each concentration of dissolved oxygen the period of survival decreased as the concentration of un‐ionized ammonia increased from 0.86 to 1.96 p.p.m.

The effect of oxygen in increasing survival time was greater in the lower concentrations of un‐ionized ammonia.
THE EFFECT OF COMMERCIAL TRAPPING ON RABBIT POPULATIONS
Authors: PHILLIPS WINIFRED M.
Published: February 2008

The effect of commercial trapping on two rabbit populations in West Wales, was investigated during 1946 to 1949. On two farms rabbits were caught alive in snares, marked and released just before trapping; the total number of rabbits marked, divided by the fraction of marked rabbits recovered in the trapped sample gave an estimate of the population before trapping started. Trapping usually removed 30–40 % of the rabbits present, a proportion compatible with a careful cropping of the population. At one farm, studied for 3 years, the population increased steadily.

Breeding was intense from January to June inclusive, and from weight and age distributions it was apparent that in 1948 and 1949 considerable breeding also occurred in autumn. The sex ratio varied around a mean of about 50%.

Data are given on movements, obtained from recapture records of zog marked animals. They suggest that rabbits probably forage over an area of not more than 150 yards in diameter. The records from recaptured marked animals indicate that the mean expectation of life is about 6 months.
THE RESPIRATION OF TOBACCO LEAVES AFTER SYSTEMIC INFECTION WITH TOBACCO MOSAIC VIRUS
Authors: OWEN P. C.
Published: February 2008

The rate of CO, production per g. dry matter of the younger leaves of tobacco plants systemically infected with tobacco mosaic virus was about 10 yo less than that of comparable healthy leaves. Older infected leaves, showing well‐developed mosaic symptoms, had the same respiration rate as comparable healthy leaves. These results were independent of seasonal change in light conditions during the growth of the plants. Older leaves, but not younger leaves, of infected plants had a lower initial water content, and both absorbed less water during the experimental period, than leaves from healthy plants. The effects of TMV infection on water content were so great that the rate of CO, production per g. fresh weight was sometimes significantly increased by infection. This reversal of the apparent effect of infection on respiration rate, depending on the basis of reference may partly account for contradictory results reported previously by other workers. Other causes for contradictory results are discussed.
EFFECTS OF NUTRITION AND LIGHT INTENSITY ON SYMPTOMS OF LEAF‐ROLL VIRUS INFECTION IN THE POTATO PLANT*
Authors: WILSON J. H.
Published: February 2008

Increased nitrogen supply to potato plants infected with leaf‐roll virus greatly reduced the intensity of leaf symptoms, and caused a smaller and less consistent reduction in phloem necrosis. Application of phosphatic fertilizer initially reduced leaf symptoms, but later increased them; it increased phloem necrosis at all stages of growth. Potash slightly intensified leaf symptoms, but not phloem necrosis. Shading, which approximately halved the light intensity, reduced leaf symptoms but had no effect on phloem necrosis.

The masking of leaf symptoms by nitrogen, and by phosphorus in the early stages of growth, was closely correlated with increases in relative leaf growth rate produced by these nutrients.

Leaf rolling and phloem necrosis are considered to be independent symptoms not causally related, because they were differentially affected by nutrient supply and shading, and each could occur without the other.
THE PRODUCTION OF ANTIBIOTICS IN SOIL: II. PRODUCTION OF GRISEOFULVIN BY PENICILLIUM NIGRICANS
Authors: WRIGHT JOYCE M.
Published: February 2008

A study has been made of the conditions affecting production of griseofulvin by Penicilliiim nigricans in two types of soil, an acid, sandy podsol from Wareham Heath and a garden soil. The characteristic morphogenetic response of many fungi to low concentrations of griseofulvin was made the basis of a highly specific bioassay.

The essential prerequisites for production of griseofulvin in either soil were sterilization and enrichment with organic matter; no griseofulvin could be detected in autoclaved soil which had not been supplemented or in normal soil even when organically enriched. Garden soil was a better medium for growth of P. nigricans and production of griseofulvin than Wareham soil although this soil could be improved in this respect by liming.

The yield of griseofulvin was decreased in soil re‐infected by other soil organisms, particularly by some which were known to produce antifungal antibiotics, e.g. Penicilliunr expansum, P. frequentons and two strains of Trichoderma viride. The antagonism shown to Penicilliunz nigricuns was not entirely a matter of antibiotic activity, as some fungi believed not to produce antifungal substances had an antagonistic effect. These were mostly fungi with a characteristically rapid growth rate, e.g. Mucor rarnmannianus and one strain of Trichoderma riride. In some cases Penicillium nigricans was itself antagonistic to other fungi irrespective of their ability to produce antibiotics or of their fast‐growing habit.

The results were compared with those obtained from a previous study of the soil conditions affecting the production of gliotoxin by Trichoderma viride. A higher level of nutrient was required for the production of griseofulvin, and the effect of antagonism by other soil micro‐organisms was more important than in the production of gliotoxin by T. viride in the soil.
INSECTICIDAL ACTIVITY AND CHEMICAL CONSTITUTION: ANALOGUES AND ISOSTERES OF DDT
Authors: STRINGER A. , WOODCOCK D. , SKERRETT E. JOHN
Published: February 2008

A number of isosteres of DDT and related compounds have been synthesized and examined for insecticidal activity using the grain‐weevil, locust and cotton stainer. A marked loss of activity follows replacement of the chlorine atoms of DDT by methyl and hydroxyl groups. In the nitroalkane series, the optimum structure for maximum toxicity was present in i:i‐di‐/>‐chlorophenyl‐2‐nitropropane. The significance of these results has been reviewed in the light of current theories of DDT structure and activity. Many of the compounds expected to be toxic were found not to be so, and this inactivity can be attributed either to the initial hypotheses being invalid or to the operation of biological factors preventing concentration of the compound at the site of action.
TRANSMISSION OF GROUNDNUT ROSETTE VIRUS
Authors: STOREY H. H. , RYLAND A. K.
Published: February 2008

The rosette virus was transmitted to groundnut plants, if previously etiolated, bymechanical inoculation of juice with ‘Celite’ addition; but only a small proportion of the inoculations succeeded.

Aphis craccivora (Koch), the known vector, transmitted the virus by feeding on germinating groundnut seeds; and from this fact we developed an experimental technique that is convenient and flexible.

Different races of this species appeared to vary in inherent efficiency in transmission, and one failed ever to transmit. Within races that could transmit, all larval forms and alate and apterous adults might transmit; but alatae were sometimes significantly more efficient than apterae, and at other times the converse held. A field experiment showed that wingless forms, moving over the soil surface, might play a predominant part in secondary spread around a rosetted plant.

Comparative tests with groups of I, 2, 3 and 4 infective aphids supported the hypothesis that infections by this vector are individual and independent.

Single aphids, tested for 24 hr. on 10 successive days without access to an outside source of virus, might infect on any day up to the tenth. Similar results were obtained in a succession of I hr. tests on a single day. In the infected seed the virus rapidly became available to feeding aphids; previously non‐infective aphids acquired the virus by feeding on a seed during the third day from the first exposure of this seed to infective aphids.
THE RELATIONSHIP BETWEEN NICKEL‐TOXICITY SYMPTOMS AND THE ABSORPTION OF IRON AND NICKEL
Authors: CROOKE W. M. , KNIGHT A. H.
Published: February 2008

During a 70‐day experimental period from germination to maturity, the iron content of oat plants that showed symptoms of nickel toxicity changed little, but the nickel content increased rapidly for about 30 days and then decreased slowly. Necrosis varied little with time, while chlorosis increased in severity for 40 days, then decreased until unfolding young leaves were no longer chlorotic. This change in chlorotic symptoms was correlated with the nickel‐iron ratio in the plant.

Autoradiographs of leaves from plants supplied with radioactive iron showed that necrotic areas in the leaf matched areas in the autoradiograph having a very low content. Chlorotic areas were found to correspond with areas whose iron content was lower than that of healthy tissue. More iron was found in the veins than in the interveinal tissue, and its distribution was the same whether supplied as ferric citrate or in a chelated form.

The concentration of iron in mature leaves from oat plants growing in a nickel toxic soil was lowest in the necrotic areas of the leaf, suggesting a migration of nutrients out of this dying tissue.
FURTHER ASPECTS OF THE RELATIONSHIP BETWEEN NICKEL TOXICITY AND IRON SUPPLY
Authors: CROOKE W. M.
Published: February 2008

Absorption of nickel by oat plants increased with increasing pH for a fixed iron supply. Nickel uptake and toxicity symptoms (necrosis and chlorosis) were both reduced when the concentration of iron in the nutrient solution was high. Nickel‐iron ratio in the nutrient solution. For solutions with the same nickel‐iron ratio, toxicity symptoms increased with increase in the absolute amount of nickel. There was a linear relationship between the degree of necrotic symptoms and the nickel‐iron ratio in the plant.

Nickel consistently reduced the iron content of roots and tops. In the absence of nickel, the iron content of the roots but not of the tops, increased with iron supply. In nickel‐toxic plants, the magnesium, calcium and phosphorus contents of the tops and the potassium, calcium and phosphorus contents of the roots were higher than in healthy plants, but the potassium content of the tops and the magnesium content of the roots were lower.

Similar results were found with tomato.
THE INFLUENCE OF SOIL MOISTURE ON THE EMERGENCE OF LARVAE FROM CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHMIDT
Authors: WALLACE H. R.
Published: February 2008

The significance of soil moisture in relation to aeration and larval emergence from cysts of Heterodera schachtii Schmidt is discussed. The rate of larval emergence increased as oxygen concentration increased. A comparison of the moisture characteristics of a mass of cysts and of sand of about the same particle size showed that water was removed from between both the cysts and the sand particles at 12–16 cm. of water‐pressure deficiency. There was an indication that water was removed from between the eggs within the cysts at 100–135 cm‐ of water‐pressure deficiency. The rate of larval emergence showed a gradual decline is suction was increased beyond 20 cm. of water‐pressure deficiency, approaching zero at 175 cm. of water‐pressure deficiency. Results suggest that egg hatch is not directly dependent on pressure deficiency and that the presence of free larvae within the cyst inhibits further egg hatch. A technique is described for measuring larval motility in sand. There is a decline in motility when most of the water has been removed from the sand pore‐spaces. It is suggested that the relatively low rates of larval emergence at high‐pressure deficiencies are due to inhibition of larval migration from the cyst by the surface forces of the water film.
LOOSE SMUT (USTILAGO TRITICI (PERS.) ROSTR.) OF WHEAT: PHYSIOLOGIC SPECIALIZATION AND REACTION OF VARIETIES IN ENGLAND
Authors: BATTS C. C. V.
Published: February 2008

Three physiologic races of loose smut (named Ci, C2 and C3), found in wheat varieties grown at Cambridge, differ from those identified in Holland. The resistance or susceptibility of fifty‐seven wheat varieties to races Ci, C2 and C3 has been determined. Experiments have shown that infection of an ear can take place over a period of several days. There is a close relationship between the percentage of plants attacked and the severity of attack in a single plant.
THE EFFECT OF SUCROSE SPRAYING ON SYMPTOMS CAUSED BY BEET YELLOWS VIRUS IN SUGAR BEET
Authors: WATSON MARION A.
Published: February 2008

When leaves of sugar‐beet plants infected with beet yellows virus were sprayed daily with 10% sucrose solution, yellowing symptoms were intensified. When glasshouse plants were shaded so that the light intensity was reduced to less than half of full daylight, yellowing symptoms were suppressed more completely on un‐sprayed than on sprayed plants. Spraying with 2–5 % sucrose solution had similar, but slightly smaller effects.

Spraying with sucrose solution increased the carbohydrate content of the leaves, and the effects on symptom intensity and carbohydrate content were closely correlated. The regression coefficients of symptom score on total sugar content were nearly the same for shaded and unshaded plants. As the severity of symptoms was increased by supplying carbohydrate without change in the light conditions, it is concluded that light intensity affects symptom expression by varying the carbohydrate content of the leaves through its influence on photosynthesis.

Sucrose spraying increased the yield of roots of healthy and infected plants, and most of the increase was sucrose. This shows that sprayed sugar was translocated to the roots from the leaves of both healthy and infected plants.

Measurements of changes in carbohydrate content between evening and morning samplings confirmed that movement of carbohydrate out of infected leaves is not stopped by infection.
EFFECTS OF DARKNESS ON THE CONSTITUTION OF TOBACCO LEAVES AND SUSCEPTIBILITY TO VIRUS INFECTION
Authors: HUMPHRIES E. C. , KASSANIS B.
Published: February 2008

An attempt was made to find the causes of increased susceptibility to virus infection when tobacco plants are kept in the dark before inoculation. The changes in certain nitrogen fractions, viz. insoluble‐N, amino‐N, amide‐N, ammonia‐N and nitrate‐N, and in dry matter and water content were followed in tobacco plants subjected to a period of darkness before inoculation with tobacco aucuba mosaic virus. Only nitrate‐N was strongly correlated with the susceptibility to infection, but the evidence suggests that the correlation is indirect and not causal.

Dry matter and water content, determined either as dry matter percentage of fresh weight or measured separately on a leaf‐disk basis Ivere found to vary directly with variation in susceptibility.
THE INFLUENCE OF THE ENVIRONMENT ON SEED AND SEEDLING MORTALITY
Authors: HARPER JOHN L.
Published: February 2008

Maize grains were exposed to 16–20 combinations of soil moisture and soil temperature (1–30 C.) for varying periods of time. Grains germinated readily in the wettest soils at 30 and 200 C, but germination was inhibited at the lower levels of soil moisture, and inhibited or delayed at the lower temperatures. Grains which failed to germinate in the soil were transferred to damp sand at 200 C. and the residual viability of the samples was determined. Mortality of grain was highest at combinations of temperature and soil moisture which just did not allow of germination. Soil conditions even more unfavourable for germination gave greater residual viability in the samples. The viability of dormant grains was more rapidly destroyed at high than at low temperatures although the reduction in viability continued longer at low temperatures, probably because of the slower drying of the soil.

This mortality is interpreted in terms of pathogenic activity, and it is shown that mortality at high temperatures (20–35 o C.) is explicable on this general hypothesis. It is tentatively suggested that temperature and soil moisture conditions interact in selecting out and favouring the activity of specific populations of pathogens in the soil.
GRAZING OF WINTER CORN BY THE RABBIT (ORYCTOLAGUS CUNICULUS (L.)
Authors: GOUGH H. C.
Published: February 2008

Observations on winter corn fields being severely grazed by rabbits showed that there was usually a typical pattern of damage when the source of the rabbits was from one direction. The part of the field nearest the source of rabbits was grazed for a long period and usually failed, the part farthest from the source of rabbits was grazed lightly or not at all and usually yielded well and the central section was intermediate. The effect of severe grazing was to delay plant establishment by retarding or preventing the formation of secondary roots and tillers, so that many plants ultimately died and the survivors were small and backward.

Small plots protected by wire netting were used to demonstrate and investigate the effects of grazing, but there was no evidence that the shelter provided by the netting itself in the absence of rabbits directly improved growth within the cages. Artificial defoliation, unless it was very drastic, was not an adequate substitute for rabbit grazing, though this technique was used to confirm a field observation that oats were more susceptible than wheat to this type of damage. Some of the practical implications of the observations and experiments are discussed.
THE EFFECT OF DARKENING ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION WITH VIRUSES
Authors: WILTSHIRE G. H.
Published: February 2008

The ascorbic acid content of leaves of French bean and tobacco depends on age of the leaf and on illumination during the period immediately before harvest. There is a measurable diurnal fluctuation with the French bean. Ascorbic acid is lost within a few days from the leaves of intact plants or from detached leaves cultured in water in darkness, and from the darkened part of partly darkened leaves. The simultaneous increase in susceptibility of darkened leaves to infection by viruses was not reversed by infiltrated ascorbic acid.
THE EMERGENCE OF LARVAE FROM CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHMIDT, IN AQUEOUS SOLUTIONS OF ORGANIC AND INORGANIC SUBSTANCES
Authors: WALLACE H. R.
Published: February 2008

The rate of larval emergence from cysts of the beet eelworm in a variety of aqueous solutions containing organic and inorganic substances is significantly higher than the emergence rate in water. It is suggested that differences between larval emergence rates in monoamino‐monocarboxylic amino‐acids may be related to the lipid solubility of these substances and their ability to penetrate the egg membranes. The larval emergence rate in fructose, glucose, sucrose and maltose was significantly higher than that in water, but in raffinose, arabinose and xylose the rate of emergence was no higher than in water. A high rate of larval emergence occurred in sodium chloride, potassium chloride and mercuric chloride, but not in magnesium chloride or calcium chloride. Experiments with several other organic solutions are described. There is an optimum concentration for larval emergence in beet diffusate. The osmotic pressure of the diffusate when maximum emergence occurred was 0·48 atm. Measurements of shrinkage of unhatched larvae in various concentrations of urea, sodium chloride and sucrose showed that decreasing rates of emergence at higher concentrations may be due to changes in the unhatched larvae brought about: by an osmotic effect. High concentrations of beet diffusate may have a similar effect.
FURTHER OBSERVATIONS ON THE PATHOGENICITY OF CALONECTRIA RIGIDIUSCULA (BERK. & BR.) SACC. TO THEOBROMA CACAO L
Authors: OWEN HAROLD
Published: February 2008

Quantitative data are provided for the occurrence of Calonectria rigidiuscula and other fungi in occluded Mirid lesions and other sites in shoots of cacao plants. Mirid lesions appear to be particularly favourable for the development of C. rigidiuscula. The fungus also occurs as a saprophyte on cacao pods, and as a wound parasite in woody plants other than cacao; it was successfully introduced into plants of varied affinities by inoculation. C. rigidiuscula spreads from inoculations in cacao stems much more rapidly than other fungi. The results confirm that it is the most important fungus infecting Mirid lesions and causing dieback of cacao in West Africa.

Inoculation tests with a range of Amelonado and Trinitario clones suggested that the clones vary in their susceptibility to C. rigidiuscula, but the plant‐to‐plant variation was too great to conclude that any one is highly resistant. Various types of introduced cacao were also tested; preliminary experiments indicate that certain types of Upper Amazon cacao may be resistant, but they need further investigation.
THE BIOLOGY OF THE TWO COMMON STORAGE SPECIES OF ORYZAEPHILUS (COLEOPTERA, CUCUJIDAE)
Authors: HOWE R. W.
Published: February 2008

Oryzaephilus surinamensis (L.) and O. mercator (Fauv.) are distinct species which do not interbreed; they can be distinguished by the relative lengths of eye and temple and by the male genitalia. Both species are imported into Britain, O. surinamensis chiefly on cereal products and O. mercator chiefly on oilseed products. O. mercator is killed by cold in Britain, but O. surinamensis can survive and not infrequently becomes a pest.

Eggs hatched at temperatures from 17·5 to 40°C. Egg mortality was high below 20°C. and above 37·5°C. Low humidity also increased egg mortality but did not affect the length of the instar which was shortest at 35°C. and above. On wheat‐feed, the larva of O. mercator grew more slowly than that of O. surinamensis and was more sensitive to low humidities. The optimum for O. mercator was about 30–32·5°C. and that for O. surinamensis about 3–35°C. Low humidity increased the length of the larval period, and at 10% R.H., O. mercator died outside the range 25–32·5° C. The shortest pupal period was observed at over 35°C. On coconut meal at 30°C. and 70% R.H., O. mercator grew faster than O. surinamensis, which could not grow on this food at lower humidities. O. mercator grew more slowly on this food than on wheatfeed. Neither species completed development on groundnut meal unless yeast powder was added.

The usual number of larval moults before pupation was three, but a few individuals had four or two. The longer larval period of O. mercator is explained partly by the individual instars being slightly longer than in O. surinamensis and partly by the increased tendency for the latter species to have only two larval moults.

The preoviposition period of both species at 30 and 33°C. was 3–8 days, usually about 5. O. mercator reached a peak of three eggs per female per day and O. surinamensis of 6–10 per female per day by the end of a week and maintained these rates for a month, laying about 200 and 375 eggs per female respectively. About 95% of eggs hatched.

Both species can increase rapidly in the tropics, but neither can grow very quickly in unheated stores in Britain. O. surinamensis is a pest because it can survive in large numbers in the fabric of warehouses and multiply rapidly when warm or actively heating produce becomes available.
INVESTIGATIONS ON RESISTANCE TO DISEASE AMONG SPECIES OF THE GENUS AVENA
Authors: WILLIAMS WATKIN , VERMA U. N.
Published: February 2008

A collection of fifty‐three samples representing diploid and tetraploid species of the genus Avena was tested for resistance to three races of crown rust (Puccinia caronata avenue) and two races of stem rust (P. graminis avenae).

Resistance to some races of the two rust species was confined to one sample of subsp. strigosa and two samples of subsp. barbata of A. strigosa. Sample no. 20, representing subsp. barbata, alone possessed resistance to all the races of both rust species. This material had previously been shown to be resistant to six races of smuts (Ustilago spp.). Genotypes possessing combinations of resistance to a wide range of pathogens appear to be very rare, and intra‐specific variation in respect of these characters is so great, that taxonomic classification cannot be used with any degree of certainty to discover sources of resistance to disease.

The discovery of widespread resistance in a sample of the tetraploid subsp. barbata offers possibilities of the direct transference of genes to the cultivated species, thus dispensing with the need to synthesize amphidiploid bridging forms.

The reaction of the hexaploid variety, Richland, to stem rust proved to be sensitive to temperature. Resistance mechanisms which are subject to environmental influences are considered to be less effective in combating the evolution of new races of the pathogen.
OBSERVATIONS ON THE EMERGENCE PERIODS, LARVAL POPULATIONS AND PARASITISM OF THE CABBAGE ROOT FLY (ERIOISCHIA BRASSICAE BCHE)
Authors: MILES MARY
Published: February 2008

At Wye the overwintering generation of Erioischia brassicae emerged in captivity in a sharply defined period lasting from 4 April to 3 May 1954 and 75% (53 flies) emerged from n to 19 April.

The emergence period for first‐generation flies in 1954 was from 28 June to 24 September. There was no well‐defined peak period; flies emerged almost every day from 28 June to 16 August, with the highest numbers (11 flies per day) on 16–17 July and the greatest concentration of emergences (76 flies, 41%) from 11 to 21 July. In 1955, first‐generation flies emerged from 24 June to 23 August, with a peak emergence period from 6 to 16 July when 50% (348 flies) emerged. The differences between the times of peak periods of emergence in the 2 years were associated with differences in temperature in June and July; cooler weather appeared to delay emergence.

Counts of first‐generation larvae and puparia of E. brassicae in the latter half of June 1955 showed average populations of 59 per plant with a maximum of 132 per plant. Counts after exposure to attack during July and from mid‐August to November showed an average infestation of less than two per plant. Plants exposed to attack from mid‐May onwards until December showed average populations of 15 puparia per plant only two of which were viable. This gave further evidence that high infestation by E. brassicae occurs only in spring.

Larvae and puparia collected in June were allowed to complete their development in captivity. In 19–54 the emergences from 350 puparia were as follows: 188 flies (54%); 145 (41%) Trybliographa rapae Westw., a Cynipid (Hymenoptera) parasite; and 17 (5%) Aleochara bilineata Gyll., a Staphylinid beetle parasite. In 1955 the emergences from 990 puparia were 693 (70%) flies, 296 (30%) Trybliographa rapae and one Aleochara bilineata. The samples consisted of larvae and puparia in a ratio of about 3 : 1 and were therefore biased in favour of Trybliographa rapae. Observations on dates of emergence showed that in samples consisting wholly of viable puparia drawn after mid‐July, there is likely to be a bias in favour of the parasites because the peak of emergence of first‐generation flies has already passed.
THE EFFECT OF ORGANOPHOSPHORUS INSECTICIDAL SPRAYS ON THE GROWTH AND PHOSPHORUS CONTENT OF BRUSSELS SPROUTS
Authors: THORNE GILLIAN N.
Published: February 2008

No evidence was found that the insecticides schradan or demeton directly increase the growth of plants. The dry weight of Brussels sprouts plants grown in soil supplying little phosphorus was unaffected by spraying six times with schradan or demeton, or with sodium phosphate Solution supplying the same amount of phosphorus as the insecticides. The dry weight of larger plants grown in soil supplying more phosphorus was unaffected by spraying with demeton or inorganic phosphorus Solutions; schradan spray decreased it in one experiment but not in the other.

Spraying with schradan, or with the equivalent amount of phosphorus as sodium phosphate, in one experiment increased the phosphorus content of plants grown in soil supplying little phosphorus. With high phosphorus supply in the same experiment, sodium phosphate Solution, but not schradan, increased phosphorus content of the plants slightly, but not significantly. Phosphorus content was not affected either by schradan sprays in the other experiment or by demeton sprays in both experiments.
THE INSECTICIDAL ACTIVITY OF SOME ORGANOPHOSPHORUS COMPOUNDS AGAINST THE MIGRATORY LOCUST (LOCUSTA MIGRATORIA MIGRATORIOIDES REICHE & FAIRM.)
Authors: STRINGER A.
Published: February 2008

Although the insecticidal effectiveness of a compound is dependent on many factors, such as Solubilities and detoxification, there appear to be distinct relationships between chemical structure and insecticidal activity. The insecticidal activity of paraoxon was significantly greater to the adult males of Locusta migratoria migratorioides than that of all other nitrophenyl‐phosphorus compounds tested. This may be attributed to the direct action of the compound, involving no change from inactive to active form in vivo, and also to a better translocation of the compound from the point of application to the site of action. The toxicity of injected paraoxon was of the same order as that topically applied. Parathion, its isomers, and ethyl p‐nitrophenyl phenyl phosphonothionate (EPN) were approximately equivalent, whereas malathion, although relatively low in toxicity, with an ED50, of 29 μg./insect, was still a reasonably effective insecticide. Methyl, ethyl and iso‐propyl esters were effective in that order of toxicity. Substitution of other alkoxy or aryloxy groups resulted in loss of activity.
INVESTIGATIONS REGARDING THE NATURE OF THE INTERACTION BETWEEN IRON AND MOLYBDENUM OR VANADIUM IN NUTRIENT SOLUTIONS WITH AND WITHOUT A GROWING PLANT
Authors: WARINGTON KATHERINE
Published: February 2008

Iron offset the toxicity of molybdenum or vanadium in nutrient solutions more effectively when it was supplied at the same time as the molybdenum or vanadium than when it was given separately in alternate 3‐day periods.

Allowing nutrient solutions of pH 4.6 containing high concentrations of iron, with or without vanadium, to stand for 4 days before use did not delay the restoration of colour to chlorotic plants, but even z days' standing reduced the iron content of their roots and the vanadium content of both shoot and root. The presence of vanadium had little effect on iron uptake.

In parallel experiments with molybdenum, standing the solutions for 7–9 days before use delayed colour recovery, but shorter periods had no effect. Standing for z days or longer greatly reduced the iron content of the root, but the molybdenum content was unaffected or increased. High molybdenum greatly increased the iron in the root, but had little effect on that in the shoot.

Precipitation of iron in the nutrient solution was delayed by high concentrations of either ammonium or sodium molybdate if the initial pH was 4.6, but not if it was 6.6. Vanadium had no influence on the precipitation of iron at pH 4.6.

At least part of the compensating action of iron on molybdenum or vanadium toxicity would appear to take place outside the plant.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M.
Published: February 2008

Extracts of the coats of seeds inoculated with Trichoderma viride, Penicillium frequentans or P. gladioli and sown in soil contained antibiotics, identified by paper chromatography as gliotoxin, frequentin and gladiolic acid respectively. Three actinomycetes, Streptoniyces griseus, S. venezuelae and S. nureofaciens failed to produce an antibiotic in the coats of seeds sown in either John Innes potting compost or a calcareous soil.

When uninoculated pea seeds were sown in a soil in which an unintroduced gliotoxin‐producing strain of Trichoderma viride was growing vigorously, gliotoxin was detected in the seed coats.
STUDIES ON THE UPTAKE AND TRANSLOCATION OF STREPTOMYCIN BY PEACH SEEDLINGS
Authors: DYE M. H.
Published: February 2008

Measurements of the antibiotic activity in the foliage of peach seedlings, kept with their roots in mineral nutrient solutions containing streptomycin, showed that streptomycin passed into the foliage and sometimes reached concentrations above those of the solutions surrounding the roots. The amount of the antibiotic in leaves varied with the time that roots were kept in the solutions and with the streptomycin concentrations of the solutions. Lower leaves contained much more than upper leaves.

Adding macerated leaf tissue to streptomycin solutions decreased the amount of streptomycin detectable in the supernatant liquid more than could be accounted for by dilution or alteration of pH.

Streptomycin first affected plants by decreasing apical growth, but at higher concentrations it caused chlorotic and necrotic areas on leaves and stems.
STUDIES OF THE BIOLOGY OF SCLEROTIUM CEPIVORUM BERK.
Authors: SCOTT M. R.
Published: February 2008

Sclerotium cepivorum did not grow from agar into unsterile soil, but growth of restricted duration and extent was observed from infected onion tissue. Growth depended on the food reserves and its extent was determined by the size and age of the infected tissue. In sterile soil the mycelium grew only very slowly even in the presence of organic supplements. In addition to being inadequate nutritionally, unsterile soil has a microflora that interferes with the growth of S. cepivorum. It is concluded that S. cepivorum does not persist as growing mycelium in natural soils.
THE EFFECT, ON OYSTER SPATFALL, OF CONTROLLING BARNACLE SETTLEMENT WITH DDT
Authors: WAUGH G. DUNCAN , ANSELL A.
Published: February 2008

During the summer of 1955 experiments were made with DDT to control barnacle fouling of oyster spat collectors. Results showed that effective control of barnacles on artificial collectors doubled the yield of oyster spat. Shell cultch treated in the same way gave less conclusive results, partly because of the poor spatfall experienced.

Oyster spat on treated artificial collectors were approximately 40% bigger, at the end of 2 1/2 months, than those on controls. Evidence from shells, however, indicated that DDT initially inhibited the growth of oyster spat. Apparently spat become stunted in natural conditions, because they are unable to compete effectively for food with the dense barnacle populations. Competition amongst barnacles themselves also causes stunting.

The dense population of Elminius modestus on the east coast oyster grounds may have a long‐term effect on both the yield and growth of oysters.
THE ANTI‐ESTERASE ACTIVITY OF PARATHION AND SOME RELATED ORGANOPHOSPHORUS COMPOUNDS
Authors: STRINGER A. , FIELDING A. H.
Published: February 2008

The in vitro activity of cholinesterase and acetylesterase of two insect species‐ Locusta migratoria migratorioides R. &F. and Calandra granaria L.—has been examined.

There appear to be two distinct enzymes present, and in both insects their activities are at comparable levels and their inhibition by the organophosphorus compounds examined are also similar.

Compounds possessing the phosphoryl group have high inhibitory activity and those with the thiophosphoryl group have low activity in vitro.
THE CYST OF THE POTATO‐ROOT EELWORM (HETERODERA ROSTOCHIENSIS WOLLENWEBER) AS A HATCHING UNIT
Authors: ELLENBY C.
Published: February 2008

Two series of experiments are described: in one, the hatching of half and whole cysts is compared, in some cases after they have been subjected to tryptic digestion; in the second series, the hatching of free eggs is considered.

Total emergence from halved cysts was very much greater than that from intact cysts. Emergence from trypsin‐treated halved cysts was greater than emergence from control halved cysts, suggesting that the enzyme affects the egg shell or the larva inside; it is possible, however, that the enzyme also affects the cyst wall, for treated whole cysts shrink more rapidly and to a greater extent when exposed to air.

Total emergence from trypsin‐treated whole cysts did not differ significantly from that of untreated whole cysts, unlike previous findings (Ellenby, 1946 a); however, emergence began sooner from these cysts. Halving the cysts also resulted in earlier emergence, the biggest effect being produced by a combination of both trypsin and subsequent halving.

The variability shown by the intact cysts was considerably greater than that shown by the halved cysts; halving the cysts reduced the coefficient of variation from 0·55 for whole untreated cysts, to 0·19 for untreated halved cysts, and to 0·13 for trypsin‐treated halved cysts. Apparently some of the variability in emergence, like the limitation of total emergence, is bound up with the nature of the cyst as a more or less closed system.

In two experiments the hatching of eggs freed from half‐cysts was compared with that of eggs in their fellow intact halves. In one experiment there was no difference; in the other it was possible to show that a higher proportion of free eggs hatched. Evidently factors limiting hatching may operate among eggs in a mass, even though they are no longer completely enclosed in a cyst.
THE SUSCEPTIBILITY OF POTATO VARIETIES TO INFESTATION BY THE EELWORMS DITYLENCHUS DESTRUCTOR AND D. DIPSACI
Authors: GOODEY J. BASIL
Published: February 2008

Twenty‐five varieties of potato in common commercial cultivation were found to be susceptible to tuber attack by potato‐derived populations of Ditylenchus destructor under field and pot experimental conditions. Stunting and leaf deformation may also be caused by the eelworms but appear less consistently. A race of D. destructor from mushroom spawn had almost no effect on potatoes. Various races of D. dipsaci can reproduce in the shoot tissue of potato, sometimes causing damage. One population of this stem eelworm produced lesions on the tubers.
THE INFESTATION OF WINTER LETTUCE BY APHIDS AND ITS CONTROL
Authors: SMIETON M. J. , MONTGOMERY N.
Published: February 2008

Observations have been made on the infestation by aphids of winter lettuce at Imperial College Field Station, Slough, for the seasons 1947–8 and 1949–54. The effects of transplanting and of the use of insecticides have been studied.

Plants drilled in September where they were to mature were ready for cutting a little earlier than those transplanted in November, but in years when aphids were numerous the drilled lettuces were heavily infested and very few of them hearted.

The infestation of young crops varied from year to year; in some winters it fell to a low level, in others it increased rapidly and persisted with serious effect on the crop. In some years lettuce mosaic virus was also prevalent. The dominant aphid species was Nusonovia ribis‐nigri (Mosley).

An early and persistent attack, even in the absence of virus disease, much reduced the number of hearted plants and their average weight. A late attack by winged aphids in early spring sometimes spoilt fully hearted lettuces.

Dipping the plants in nicotine solution at the time of transplanting in November reduced aphid infestation; dusting with benzene hexachloride proved more effective.

If transplanting was delayed until February or March a relatively clean crop could be produced by insecticide treatment, but losses from fungal disease were usually high.