bluuebunny/crossref_metadata_2025 huggingface dataset:
INCIDENCE OF TAKE‐ALL ON WHEAT AND BARLEY ON EXPERIMENTAL PLOTS AT WOBURN
Authors: GLYNNE MARY D.
Published: February 2008

Summary.

Surveys were made in 1931, 1932 and 1933 of the incidence of take‐all on wheat and barley grown in the continuous experiments at the Woburn Experimental Station. Ten random samples consisting of all the plants in two half‐metre lengths separated by a metre and taken from adjacent rows were obtained from each plot. The numbers of clean and diseased plants, their tillers and yield of straw and of grain were determined for each sample. No manure had been applied since 1925‐6 except to certain of the barley plots.

There was little or no take‐all on plots which had received ammonium sulphate alone, with minerals, or with 1–2 tons of lime, while the disease was present in most of the other plots.

In general there was a higher percentage infection on wheat, reaching a maximum of 52.5 per cent, on one plot, than on barley in which the highest percentage infection on any plot was 16.2.

Little or no take‐all appeared on either wheat or barley in plots whose pH. was 5 or less, comparatively little at pH 5.1 and in general considerably more at higher pH values. In spite of considerable variation in infection at the same pH. values there was a general tendency for percentage infection to rise with pH in wheat, but this was not apparent in barley.

The wheat plot 10 B which had received rape dust was exceptional in that though it had a pH. of 5.4 little infection appeared. The corresponding barley plot also had little infection but its pH. was only 5.1. No clear relationship between yield and incidence of take‐all was found.

In the three years in which observations were made take‐all appeared to increase in wheat till 35 per cent, of the plants were infected and then to decrease. Two years' observations on barley suggest that the corresponding figure for this crop is about 10 per cent.

The total number of plants obtained from all the wheat samples increased slightly from 1931 to 1932 and decreased by more than half in 1933. The average percentage of take‐all increased considerably from 1931 to 1932 and remained about the same in 1933.

The average loss in yield due to take‐all in thirteen affected plots rose from 16 per cent, in 1931 to 20 per cent, in 1933, with a maximum loss in any plot of 42 per cent.

A white mycelium belonging to an Agaric of the Cortinarius type was found frequently on the roots and basal parts of wheat and barley. In general it did not appear parasitic but there is some evidence that in certain plots it had become so, causing considerable loss in yield.

Take‐all was very much less on wheat grown in alternate years with green manure intervening than on the continuous wheat.
FURTHER EXPERIMENTS ON THE ARTIFICIAL FEEDING OF MYZUS PERSICAE (SULZ.)
Authors: HAMILTON M. A.
Published: February 2008

Summary.

 A method is described for the feeding of Myzus persicae on media of which one constituent is a radioactive indicator containing polonium.

 The results show that Myzus picks up the indicator from the medium and transmits it to a leaf on which it is subsequently fed.

 The volumes imbibed are of the same order of magnitude as those imbibed by aphids under natural feeding conditions.

 A constant proportion of the amount imbibed is transferred to the leaf, from which it is deduced that the polonium is transmitted through the bodies of the aphids and not on the outsides of the stylets.

 Evidence is given to show that the virus probably behaves in the same way as the polonium.
OBSERVATIONS ON THE TIMOTHY GRASS FLY (AMAUBOSOM A ARMILLATUM ZETT.)
Authors: KING L. A. L. , MEIKLE AGNES A. , BROADFOOT A.
Published: February 2008

Summary.

 A type of damage to the inflorescence of Timothy grass, which appears to be widely distributed, has been found in the west of Scotland to be due to Amaurosoma armillatum Zett.

 Information is given as to occurrence in the field, method of attack on the plant, life history and characteristics of the insect in its different stages. Three larval instars are distinguished and the life history is noted as monocyclic.

 Two Hymenopteron parasites are recorded.

 Experiments are described which were designed to test possible methods of control (a) by soil‐treatment, (b) by deterrents.

 Of the latter an emulsion of crude naphthalene in ground‐nut oil is recommended as promising.

 It is suggested that the grass to be reserved for seed should be set apart early in the season and sprayed with this fluid at a time as near as possible to that of the egg‐laying.
SHEEP BLOWFLY INVESTIGATIONS
Authors: DAVIES W. MALDWYN , HOBSON R. P.
Published: February 2008

Summary.

The present paper is intended as the first of a series dealing with various aspects of the sheep maggot problem, especially the causes of susceptibility. Since this pest is more common in moist weather, an investigation was made of the effect of humidity on sheep maggots; also, a method was devised for studying the humidity at the base of the wool–the site of attack.

The following is a brief summary of the results obtained:

 The eggs and young larvae of Luclia sericata Mg., the sheep maggot fly, are extremely sensitive to desiccation at 37° C.

 Dry conditions prevail in the fleece near the skin, except in the region of the rump, and the relative humidity seldom exceeds 70 per cent., even during wet weather.

 These results show that the microclimate at the base of the wool is normally too dry for the development of maggots; this has been confirmed by finding desiccated eggs and larvae on sheep in the field.

 Sheep do not become infested with maggots unless predisposing conditions are present; the humidity at the base of the wool appears to be the main factor which determines susceptibility.

 The wool around the rump is often moist owing to soiling with faeces and urine, the humid conditions favouring the development of eggs and maggots.
STUDIES ON THE SECRETION OF DIASTASE AND INVERTASE BY EMPOA8CA SOLAN A DELONG (RHYNCHOTA, HOMOPTERA, JASSIDAE)
Authors: HERFORD G. V. B.
Published: February 2008

Summary.

 It has been shown that adults and nymphs of the Jassid, Empoasca solaria DeLong, are able to eject diastase into the feeding medium.

 This diastase, besides being secreted in the salivary glands, is apparently also formed by certain yeasts which are regurgitated from the gut of the insects.

 A technique is described for feeding the leaf‐hoppers on a liquid.

 The insects have also been shown to be capable of secreting an enzyme, probably invertase, which has the power of inverting pure sucrose.
EXPERIMENTS WITH FOLLICULAR AND OTHER HORMONES AND PLANT GROWTH
Authors: TINCKEK M. A. H.
Published: February 2008

Summary.

In the experiments described the writer failed to obtain accelerated growth or acceleration of flowering by presenting small quantities of ketohydroxyoestrin and theelol to flowering plants in different ways—in solution given to the roots, or by injection, or when applied to cut surfaces.

From one experiment, designed for another purpose, possible confirmation of the results of Knight and Fildes was obtained in that auxin accelerated bacterial growth.
FURTHER EXPERIMENTS ON THE FUSARIUM BULB ROT OF NARCISSUS
Authors: HAWKER LILIAN E.
Published: February 2008

Summary.

1. Experiments on the inoculation of roots of Narcissus with Fusarium bulbigenum in the autumn show that, under suitable conditions of moisture and rather high temperature, the fungus is able to penetrate and destroy the roots of all varieties tested. Under similar suitable conditions it can penetrate bulbs of susceptible varieties via the parasitised roots. It is concluded that temperature conditions in England are seldom favourable to such penetration via the young roots during the autumn.

2. Some evidence is given that penetration of the bulbs may take place via the old roots at the end of the growing season when soil temperature is likely to be more favourable to attack. Further work on this point is desirable.

3. Gregory's statements that heavy losses from Fusarium may follow the standard hot‐water treatment against bulb eelworm, when carried out in the autumn, and that in such cases penetration usually takes place at the base of the bulb are confirmed and amplified.

4. Experiments in which bulbs were hot‐water treated, with the addition of Fusarium spores to the water, at intervals during the storage period, indicate that bulbs pass through, a phase of minimum susceptibility in late August and early September, i.e. at the normal time of bathing.

5. It has been shown that, where bulbs are hot‐water treated in the presence of Fusarium spores, the addition of formalin (0.1 per cent. or more) to the water materially reduces the resulting losses.

6. A comprehensive series of experiments, with fourteen varieties, has been carried out during four seasons in order to test the effects of the addition of fungicide to the hot‐water bath. These experiments, for reasons which are discussed fully in the text, have not yielded any conclusive evidence on the effect of this treatment on the spread of the disease. It has been amply shown, however, that the incorporation of 0.1‐1.5 per cent. formalin in the bath has no harmful effects on foliage, date of flowering, quality and number of blooms or amount of increase in weight of bulbs during the growing season, but is often beneficial.

7. Cold steeps in 0.1 per cent. mercuric chloride solution led to a retardation of the date of flowering.

8. It is desirable that fungicidal treatment should take place before the normal date of hot‐water treatment, and experiments are in progress to test the efficacy of various cold steeps and dry dustings carried out in the early part of the storage season.

In conclusion the writer wishes to express her thanks to Prof. W. Brown, who suggested this work, for much advice and assistance during its progress. Thanks are also due to Dr A. K. Ghamrawi who carried out some of the observations in the 1931 experiments.
STUDIES ON EUROPEAN FOUL BROOD OF BEES
Authors: TARR H. L. A.
Published: February 2008

Summary.

An unidentified bacillus which appears to replace B. alvei in certain cases of European foul brood has been isolated from two different cases of this disease.

Strains of B. alvei from various sources exhibit certain differences in their fermentative powers, and it is suggested that these may form a basis for differentiating strains of this organism.

The etiology of European foul brood is discussed.
A NEW VIRUS DISEASE OF THE TOMATO
Authors: SMITH KENNETH M.
Published: February 2008

Summary.

A new virus disease of the tomato plant is described. An account is given of the symptoms produced on a variety of host plants, mostly in the Solanaceae. Some of the physical properties of the virus have been investigated and its particle size measured by ultrafiltration through Gradocol membranes. The size as measured by filtration in plant sap is approximately 17–25 mμ. The virus is compared with other viruses commonly affecting tomato and tobacco and methods of differentiating them are discussed.
AN ACCOUNT OF THE CONSTITUTION AND USE OF AN ATOMISED WHITE OIL—PYRETHRUM FLUID—TO CONTROLPLODIA INTERPUNCTELLAHB. ANDEPHESTIA ELUTELLAHB. IN WAREHOUSES
Authors: POTTER C.
Published: February 2008

Summary.

 The problem of the infestation of imported stored products by the Phycitid moths,Ephestia elutellaHb. andPlodia interpunctellaHb., is outlined.

 An outline account is given of the life history ofEphestia elutellaHb. andPlodia interpunctellaHb. in the London warehouse.

 The specification of the insecticidal material used is given, together with a description of its properties and the factors influencing its choice.

 An account is given of inflammability tests on the material when in an atomised state.

 The apparatus used is described.

 The process as used against moths is described.

 The process as used against migrating larvae is described.

 The precautions which should be taken by operators are given.

 An account is given of a series of biological tests and observations made on the effects of this material and process on the moths and larvae ofPlodia interpunctellaHb. andEphestia elutellaHb.
ON THE OCCURRENCE OF APLANOBACTER RATHAYI E. F. SMITH ON DACTYLIS GLOMERATA IN ENGLAND
Authors: DOWSON W. J. , D'OLIVEIRA M.
Published: February 2008

The occurrence of baeteriosis of D. glomerata, with which is associated the non‐motile organism A. Rathayi E. F. Smith, is recorded for Cambridgeshire definitely for the first time, but there seems little doubt that the disease has been present unrecognised for some time and is being constantly introduced on imported Danish seed.

The disease is similar to that originally observed near Vienna in 1897, but differs from the latest account from Germany where the damage caused was far more severe. The general symptoms were partial or complete destruction of the spikelets which were embedded in a bright yellow bacterial slime.

The associated organism was isolated and found to agree exactly in its cultural and growth characters with the descriptions of Rathay and Smith.

The naturally occurring bacterial slime proved pathogenic when inoculated into a healthy shoot of Dactylis, but no infection resulted when pure cultures on artificial media were used.
A COMPARISON OF CERTAIN FOREIGN AND AMERICAN POTATO VIRUSES1
Authors: KOCH KAKL , JOHNSON JAMES
Published: February 2008

Potato viruses obtained from nine foreign countries have been compared with typical American forms. The chief emphasis has been placed on the potato “mottle,”“ring‐spot,” and “veinbanding” viruses.

The mottle and ring‐spot viruses were found in potatoes from all nine foreign countries, but only in about one‐half of the 75 varieties or lots tested. Hence these viruses appear to be less widespread in foreign than in standard American potato varieties. The veinbanding virus was found in potatoes from six of the nine foreign countries, and was often free from associated viruses.

The remarkable constancy of the viruses secured from widely different sources, when compared under identical conditions, was outstanding. Some degree of variation was found in certain cases, as for example between the veinbanding virus and the Y virus from England, though these viruses are very similar in most respects.

The possible relationships of certain other potato viruses are discussed, and a potato streak virus is briefly described.

Incomplete or unsatisfactory descriptions and synonomy in nomenclature are believed to be largely responsible for the existing confusion in potato virus literature. These difficulties may largely be overcome by devoting more attention to the description of the viruses themselves.
THE PHYSIOLOGY OF VIRUS DISEASES IN PLANTS
Authors: CALDWELL JOHN
Published: February 2008

Experiments on the purification of the virus of yellow mosaic of tomato are described and discussed. Vinson and Petre's methods of purification of the virus from infectious juice and subsequent elution with phosphate solution were slightly modified in these experiments. It was found that there was no evidence that the virus could be recovered in a crystalline form and that viruliferous material always contained traces of organic nitrogen. This virus was found to be active over a wide range of pH, viz. from 2.0 to 10.5. At the extremes of the scale, the excessive acidity or alkalinity was toxic to the inoculated leaves and adjustments had to be made before inoculation. Different protein precipitants were used in an attempt to free the virus from the proteins, and electrolytic methods were also tried. Proteolytic enzymes were employed on the purified virus juice but the results were rather unsatisfactory. Difficulty was experienced in ensuring that the effect of some reagents was on the virus and not on the tissues of the test plants.
THE CALCULATION OF THE DOSAGE‐MORTALITY CURVE
Authors: BLISS C. I.
Published: February 2008

The sigmoid dosage‐mortality curve, secured so commonly in toxicity tests upon multicellular organisms, is interpreted as a cumulative normal frequency distribution of the variation among the individuals of a population in their susceptibility to a toxic agent, which susceptibility is inversely proportional to the logarithm of the dose applied. In support of this interpretation is the fact that when dosage is inferred from the observed mortality on the assumption that susceptibility is distributed normally, such inferred dosages, in terms of units called probits, give straight lines when plotted against the logarithm of their corresponding observed dosages. It is shown that this use of the logarithm of the dosage can be interpreted in terms either of the Weber‐Fechner law or of the amount of poison fixed by the tissues of the organism. How this transformation to a straight regression line facilitates the precise estimation of the dosage‐mortality relationship and its accuracy is considered in detail. Statistical methods are described for taking account of tests which result in 0 or 100 per cent, kill, for giving each determination a weight proportional to its reliability, for computing the position and slope of the transformed dosage‐mortality curve, for measuring the goodness of fit of the regression line to the observations by the X2 test, and for calculating the error in position and in slope and their combined effect at any log. dosage. The terminology and procedures are consistent with those used by R. A. Fisher, who has contributed an appendix on the case of zero survivors. Except for a table of common logarithms, all the tables required to utilise the methods described are given either in the present paper or in Fisher's book. A numerical example selected from Strand's experiments upon Tribolium confusum with carbon disulphide has been worked out in detail.
THE INTERNAL TEMPERATURES OF ‐FRUIT‐TREE BUDS
Authors: GRAINGER JOHN , ALLEN A. L.
Published: February 2008

SUMMARY AND CONCLUSIONS

The temperatures of dormant and opening fruit buds of apple, black currant and raspberry have been investigated by thermoelectric methods.

Apple buds are warmer than the air by day, and usually cooler at night. Warming seems to be effected by radiation from the sun, since a screened bud was cooler than the air during the daytime as well as at night. Cooling would seem t o be a direct result of evaporation from the bud, with radiation as an important secondary factor on clear nights.

Black currant and raspberry buds are usually cooler than the air at all times. Buds of these plants were opening, whilst apple buds were dormant, and it would seem that loss of heat by evaporation dominates even the warming effect of the sun during the day.

Apple buds seem to have a mechanism of resistance against frost, whilst no evidence of such protection has been found in black currant buds.

Results are discussed further under the various headings of the text.

In eonclusion, we desire to express our sincere thanks to Prof. J. H. Priestley for extensive help in the prosecution of the investigation here recorded, to Mr J. W. Eves of Leeds University, and to Mr A. Potts of the Fruit Station, Osgodby, for valuable assistance in obtaining the 1932 records.
TULIP FIRE
Authors: BEAUMONT A. , WESTON W. A. R. DILLON , WALLACE E. R.
Published: February 2008

The salient points that deal with the disease of tulip fire are discussed, its names, the various forms of the disease such as fire, spot and a rot of the bulb, the symptoms of these, the distribution of tulip fire, its economic importance, its host specialisation and the relative susceptibility of varieties to it.

The life history of the organism causing it, Botrytis Tulipae (Lib.) Lind is given, and the formation, germination, viability, and development of conidia and sclerotia in natural and artificial media are discussed. Infection studies in the laboratory and field with conidia and sclerotia are described, and the meteorological factors that favour artificial or natural epidemics.

Observations and experiments dealing with control measures are given.

Concluding this study the writers wish to acknowledge with sincere thanks the assistance given by growers and those otherwise interested in the cultivation of this crop, particularly to those that have given land, material, and the benefit of their experience.

A. Beaumont thanks Messrs Tomlin Bros., Penzance, for supplying bulbs for experiments and much information on spraying and dusting.

W. A. R. Dillon Weston thanks Mr H. Goude, the Horticultural Superintendent for Norfolk; Mr E. Cave, of Terrington St Clement,

Norfolk, for land, material and his valuable observations and co‐operation; Mr W. Leake, of Messrs R. H. Bath, Ltd., Wisbech, for information on the susceptibility of varieties, and Mr J. R. Booer, of Messrs F. W. Berk and Co., Ltd., for the preparation of chemicals for work on bulb disinfection.

E. R. Wallace thanks his colleagues at the Agricultural Institute, Kirton, and many growers in the Spalding district.
THE ORIGIN OF AN EARTHY OR MUDDY TAINT IN FISH
Authors: THAYSEN A. C.
Published: February 2008

Certain types of Actinomyces produce a pungent odour which has frequently been described as “earthy”. This odour is caused by an organic compound which is slightly soluble in water, volatile in steam, soluble in ether, and partly soluble in alcohol. In concentrated form the substance forms a brown amorphous material with a penetrating manurial odour.

When dissolved in water in concentrations as low as two parts in ten million it imparts to the water a pungent Actinomyces or “earthy” taint which is particularly noticeable when the reaction of the water is maintained on the alkaline side of the neutral point.

The existence of an excessive contamination of an important salmon river with odour‐producing actinomycetes was established. This contamination and the resultant pollution of the water with a pungent “earthy” taint was restricted to the tidal part of the river, where decaying organic matter was abundant.

Acknowledgment is due to the Inspector of Salmon Fisheries for Scotland for his interest in the work. Thanks are also due to the Director of Chemical Research in the Department of Scientific and Industrial Research for facilities afforded in publication of the results of these experiments with which the Water Pollution Research Board of the Department has also been concerned.
THE ORIGIN OF AN EARTHY OR MUDDY TAINT IN FISH
Authors: THAYSEN A. C. , PENTELOW F. T. K.
Published: February 2008

A muddy or “earthy” taste can be imparted to the flesh of trout by material produced by an odoriferous Actinomyces.

The taste resembles that imparted by a natural mud rich in actinomycetes.

The taint appears to be acquired through the gills and to be carried in the blood stream.

The taint can be slowly removed by clean flowing water.

The authors wish to express their thanks to the Director of Fishery Investigations of the Ministry of Agriculture and Fisheries for permission to publish these results, and to the Inspector of Salmon Fisheries for Scotland for his interest in the work. Acknowledgment is also due to the Director of Chemical Research in the Department of Scientific and Industrial Research for facilities afforded in publication of the results of these experiments with which the Water Pollution Research Board of the Department has also been concerned.
THE SORGHUM MIDGE IN THE ANGLO‐EGYPTIAN SUDAN
Authors: COWLAND J. W.
Published: February 2008

The sorghum midge, Contarinia sorghicola (Coq.), is reported for the first time from the Anglo‐Egyptian Sudan.

A short account is given of the distribution, life history, damage and control of this midge as it occurs in the Anglo‐Egyptian Sudan.
THE QUANTITATIVE DISTRIBUTION OF BORON IN VICIA FABA AND GOSSYPIUM HERBACEUM
Authors: MCLEAN R. C. , HUGHES W. L.
Published: February 2008

The content of boron in the tissues of plants, grown in solutions of known concentration, has been ascertained in‐ Vicia Faba and Gossypium herbaceum.

The distribution of boron is regular and definite. The highest percentage, per unit of dry weight, is in the leaves, increasing regularly with the age of the leaf. The petioles and the stem apex are approximately equal in percentage content, and have both approximately double the stem concentration. The roots have much the lowest concentration, only 0–07 of that in the stem.

This distribution of boron does not appear to be entirely due to passive transportation in the transpiration current.

Boron is also present in seed grown on ordinary soil, but is confined to the cotyledons, the percentage content, in Vicia, being 50 per cent, above that of the plant stems.

The amounts of boron absorbed are extremely small, though there is some storage in the tissues, and they are not directly dependent on the concentration supplied. The amounts are too small to allow of boron being regarded as a nutrient in the ordinary sense. Its importance is more probably that of an activator or regulator of metabolic processes.
THE BIOLOGY OF OAT SMUTS
Authors: WESTERN J. H.
Published: February 2008

The progress of the mycelium of two forms of Ustilago Avenae within resistant and susceptible hosts has been described and attention drawn to differences between them.

Form Lx on Avena strigosa was found to persist longer than form L11 on the variety Potato, althouch both of these Oats failed to produce infected panicles with these smuts.

The response of the resistant variety, Markton, to attack by six collections of Ustilago Avenae and U. Kolleri was found to vary considerably. Forms C1 and L11 failed to penetrate, while form C2 entered easily and the mycelium persisted for some time.

The types of sheathing structures around the penetrating tubes have been found in Markton inoculated with forms C1 and C4. Their reaction to microchemical tests was investigated.

A hypersensitive reaction resulting in the formation of necrotic areas around the parasite hyphae has been found in Markton invaded by forms C4,L1 and L2.

The varieties studied have been classified according to the grade of resistance offered to particular forms of smut. Five grades have been described.

In oats, resistance to smut is expressed in at least three ways, (i) a reaction of the epidermal cell wall which prevents penetration, (ii) necrosis of host cells, and (iii) a retarding effect on the growth of mycelium within the host.
A TEMPERATURE STUDY OF PYTHIUM ATTACK ON SWEDE SEEDLINGS
Authors: GREEVES T. N. , MUSKETT A. E.
Published: February 2008

The type of seedling disease caused by Pyihium attack on swede seedlings is closely correlated with the temperature under which the plants are raised. Low temperature conditions favour the occurrence of the pre‐emergence phase of disease and produce no damping‐off. Medium temperatures also produce no damping‐off and result in a big reduction in the pre‐emergence phase. High temperatures show the pre‐emergence phase at a minimum but encourage damping‐off.

The disease in general is likely to be best evaded by germinating the seed under conditions of high temperature until the emergence of the seedlings. The temperature should then be lowered in order to encourage the production of sturdy seedlings not likely to be subject to damping‐off.

In these experiments the disinfection of the seed with an organic mercury compound prior to sowing did not secure any control of the disease.

The two varieties of swede used–Tipperary and Ideal–proved to be equally susceptible to the disease.
A STUDY OF THE FOOD RELATIONS OF THE LYCTUS POWDER‐POST BEETLES
Authors: PARKIN E. A.
Published: February 2008

The histology of the larval gut of Lyctus is described: owing to the absence of salivary glands and caeca, the digestive juices must be secreted by the midgut with doubtful contribution from the hindgut.

The mycetomes contain organisms which are apparently not symbiotic in relation to digestion.

The skeletal substance of wood passes through the larval gut unaltered, nourishment being derived from the cell contents.

A substance, soluble in water at 60o C, is necessary in oak sapwood for normal larval development.

Larvae are unable to develop in wood from which starch is absent.

Larvae living in wood containing relatively little starch may take two years to complete their development, instead of the normal one year.

Enzymes capable of hydrolysing starch, maltose, sucrose, lactose and protein were detected in tissue suspensions of the gut and its contents.

By feeding larvae on artificial diets it has been shown that starch, sugars and protein are necessary constituents of the larval food. Furthermore, larvae have been reared to the imaginal stage on a substrate which contains no wood.

The ability of the female beetles to determine the suitability of wood for larval development is demonstrated and the importance of the so‐called “tasting” marks discussed.

An account is given of the occurrence of starch in timber and the difficulties involved in its estimation and removal from the wood.
REPORT OF THE COUNCIL OF THE ASSOCIATION OF APPLIED BIOLOGISTS FOR THE YEAR 1935
Authors: FOX‐WILSON G. , STOUGHTON R. H.
Published: February 2008

Hon Secretaries
THE SUSCEPTIBILITY OF THE PLANT CELL TO VIRUS DISEASE
Authors: SHEFFIELD F. M. L.
Published: February 2008

A number of spraying experiments showed that the virus cannot enter a plant unless some of the cells are injured. It is not essential that such injury should be brought about in the presence of the virus. The chances of infection fall off rapidly in the first few minutes after injury, but infection occurs occasionally as long as half an hour after the cell is damaged.

Inoculations by micropipette into single cells of the host plant yielded only about one‐tenth of the expected number of infections. This suggests differences in the susceptibility of the cells to virus attack.
A COMPARATIVE STUDY OF LACTOBACILLI FROM GRASS SILAGE AND OTHER SOURCES
Authors: ALLEN L. A. , HARRISON J.
Published: February 2008

Samples of 152 strains of lacto bacilli isolated from six different types of grass silage, which had been subjected to various treatments at the time of ensiling, and five strains isolated from other sources for comparative purposes, were tested by their reactions in litmus milk, yeast extract litmus milk, dextrose litmus milk, yeast extract dextrose litmus milk and in various carbohydrate broths. The metabolic products formed from dextrose by nineteen selected strains were identified and estimated.

The evidence obtained in this way pointed to the conclusion that the majority of lactobacilli in grass silage are strains of Streptobacterium plantarum, characterized by comparative inactivity in ntmns milk, bat markedly stimulated by addition of yeast extract. They produce from dextrose mainly lactic acid (usually the inactive form) with a small quantity of acetic acid. A strain was encountered which also produced alcohol and butyric acid, but the numbers of this type in silage was negligible. Considerable differences were found in the ability of the various strains to ferment carbohydrates.

Of the five strains isolated from dairy products three woe of the Streptobacterium plantarum type and two were of a kind which rapidly clotted litmus milk and exhibited reactions corresponding to the true milk strains.

The authors wish to record their thanks to the Research Council of Imperial Chemical Industries, Ltd., for a grant which rendered this work possible, to Dr S. J. Watson for supplying samples of grass and silage, and to Dr J. 6. Davis for valuable suggestions.
ON THE OCCURRENCE IN ENGLAND OF THE PEAR FRUIT SAW‐FLY, HOPLOCAMPA BEE VIS KLUG
Authors: THOMAS I.
Published: February 2008

Larvae of Hoplocampa brevis Klug., the Pear Fruit Saw‐fly, have been found attacking pears in two gardens in Cambridge. In some continental countries this is a serious pest of pears; this is the first record of damage by this pest in England.

A preliminary study of the biology of this species has been made, and the egg, larval stages and cocoon have been briefly described.

The writer is indebted to Dr H. W. Miles for the identification of the saw‐fly and for helpful criticism.
THE COMMON RUSTIC MOTH, APAMEA {H ADEN A) SECALIS L., ATTACKING WINTER CEREALS
Authors: PETHERBRIDGE F. R. , THOMAS I.
Published: February 2008

An account is given of damage to winter cereals by larvae of the Common Rustic Moth (Apamea secalis L.).
OBSERVATIONS ON THE BLACK‐STEM DISEASE OF LUCERNE IN BRITAIN
Authors: TOOVEY F. W. , WATERSTON J. M. , BROOKS F. T.
Published: February 2008

Black‐stem disease of lucerne, which may result in a serious loss of herbage, is recorded in this country for the first time.

The disease first appears on the young shoots early in spring. It is characterized by large, irregular, brownish or blackish lesions on the leaves, petioles and stems. Severe attack of the stems may involve the formation of “cankers” and may lead to wilting and death of the shoots.

The cause of the disease is a species of Ascochyta which has been determined as A. imperfecta Peck. The dimensions of the spores and the percentage of uniseptate spores in the pycnidia are extremely variable. Some field collections and cultures of the fungus possess only “phomoid” (i.e. unicellular) spores.

The characteristics of the fungus in culture are described. It has been compared with cultures of Ascochyta imperfecta Peck and Phoma Medicaginis Malbr. & Roum. from North America. All the American cultures agree with the fungus isolated from black‐stem disease of lucerne in Britain. It is concluded that the fungus which has been referred to as P. Medicaginis Malbr. & Bourn, in the United States is synonymous with Ascochyta imperfecta Peck. This opinion is substantiated by the formation of identical types of lesions on lucerne by the cultures sent from North America and by the British fungus in simultaneous inoculation experiments.

Herbarium material of Phoma Medicaginis and Ascochyta imperfecta, including type material of the latter, sent from the United States has been compared with British material of the black‐stem disease of lucerne. It is concluded that the fungus in all these collections is the same, viz. A. imperfecta Peck.

Under artificial conditions A. imperfecta can also infect Medicago lupulina and TrifoUum pratense, but it has not been found on these hosts in the field.

Ascochyta imperfecta overwinters by means of pycnidia in dead lucerne stems.

The black‐stem disease of lucerne can be held in check by early cutting of the first crop each season.
THE CONTROL OF COMMON SCAB (ACTINOMYCES SCABIES (THAXT.) GÜSS.) OF THE POTATO BY TUBER DISINFECTION
Authors: CAIRNS H. , GREEVES T. N. , MUSKETT A. E.
Published: February 2008

This investigation deals with an attempt to determine the value of seed tuber disinfection as a method for controlling common scab (Actinomyces scabies (Thaxt.) Güss.) of the potato crop when tubers affected with the disease are used for planting.

A résumé is given of previous work by other investigators dealing with the control of this disease.

Under Northern Ireland conditions it has been found that a satisfactory control of the disease may be obtained by the disinfection of afEected seed tubers before planting providing that a sufficient interval has elapsed between the growing of successive potato crops in the same land. After a 6‐year interval, which is normal in Northern Ireland farm practice, satisfactory control was obtained in all cases, and it is suggested that a 4‐year interval would probably be sufficient to ensure satisfactory results. Although good control has been obtained after the lapse of shorter intervals, such is not always the case, and the method cannot be relied upon with certainty. No control was obtained where no interval elapsed between the taking of successive potato crops.

Solutions of mercuric chloride, formaldehyde, copper sulphate, Burgundy mixture and proprietary organic mercury compounds employed in various ways were used in these experiments. The most satisfactory method for the farmer's use was found to consist of the instantaneous dipping of the tubers in solutions of proprietary organic mercurials.

The results obtained indicate that in some cases the planting of very slightly afEected seed in land which has not carried potatoes for many years may result in a high incidence of the disease in the resultant crop.

A slight depression in growth was sometimes observed to result from the planting of disinfected tubers, and this was particularly noticeable in the case of the variety Majestic. After a period of from 10 to 12 weeks it disappeared and the crop grew out normally. In some cases tuber disinfection stimulated the growth of the plants. Some of the results obtained suggest an increase in tuber yield due to disinfection of the seed tubers, but the experiments were not laid down in such a way as to permit a statistical analysis of the yields being made.
STUDIES IN BACTERIOSIS
Authors: LACEY MARGARET S.
Published: February 2008

Strains of a bacterium causing fasciation of sweet peas have been isolated from galls on Nicotiana glutinosa, asparagus, Heuchera sanguinea and Gladiolus in addition to the host plants reported in a previous paper. These four new strains all produced fasciation on inoculation into sweet‐pea seedlings.

Histological examination of sweet‐pea seedlings 2–11 weeks after inoculation showed that abnormal growth occurred in the hypocotyl region. In certain areas bacterial zoogloea formed a film on the outside of the tissue, and some penetration of bacteria into the epidermal cells, and in later stages into the intercellular spaces, was observed.

Reisolation tests confirmed the evidence from the microscopical examination, that the pathogen is mainly confined to the exterior of the tissue.

A comparison is made between the action of the sweet‐pea organism and Bad. tumefaciens in causing abnormal plant growths.
EXPERIMENTS ON THE RESISTANCE OF THE FLOUR MOTH (EPHESTIA KVHNIELLA ZELL.) TO ABNORMALLY HIGH TEMPERATURES
Authors: MANSBRIDGE G. H.
Published: February 2008

Experiments are described on the resistance to heat of E. kühniella in all its stages.

With eggs exposed to 45oC. (113o F.) and 47oC. (116‐5o F.) it is seen that:

One‐day‐old eggs are more resistant than older ones.

Eggs are more resistant to heat at low than at high humidities.

Eggs appear to be able to cool themselves at low humidities in a high temperature by the evaporation of water.

After heating, eggs can regain water they have lost if they are kept in a moist atmosphere.

After heating at low humidities, there is a bigger survival if the eggs are kept in a moist atmosphere than if they are kept in a dry atmosphere.

There is great variation in stock direct from a mill. Eggs from different pairs of moths may have widely different degrees of resistance.

Stock which has been inbred in the insectaries for twelve generations, shows less variation in resistance than stock direct from a mill.

Larvae are much less resistant than eggs. Newly hatched larvae and all larvae until they are full grown have about the same resistance. Last‐stage larvae are far more resistant than other larvae.

Pupae are more resistant than feeding larvae.

Adults are the most susceptible stage to heat. At low humidities the females are more resistant than the males.

Experiments on all stages in undisturbed cultures show that a temperature of 45–46o C, maintained for 3 hours, kills all stages.

This work was carried out under the direction of Prof. J. W. Munro, to whom I am grateful for his constant encouragement. I have to thank Mr G. V. B. Herford for his help in devising and constructing the apparatus and reading through the typescript, and I am also indebted to Dr 0. W. Richards for his helpful advice on many occasions, and to Mrs Richards who kindly supplied me with a highly inbred strain of E. kühniella. Lastly I thank Dr G. Fraenkel for many important suggestions, especially those contained in the discussion.
THE USE OF NUMBERS OF INFECTIONS FOR COMPARING THE CONCENTRATION OF PLANT VIRUS SUSPENSIONS: THE EFFECT OF CARBON ON THE PRODUCTION OF LESIONS BY VIRUSES OF THE TOBACCO MOSAIC GROUP
Authors: BALD J. G.
Published: February 2008

Tests were made of the spreading power of suspensions of plant juice, finely divided carbon, a commercial spreader, and water on leaves of Nicotiana glutinosa and paraffin wax surfaces.

The contact angle of the suspensions of the plant juice and the “spreader” was lower than that of water and suspensions of carbon.

When rubbed over the surface the plant juice and “spreader” gave good contact compared with the water, and the particles of carbon adhered to the surface carrying with them a film of water.

The effect of carbon and plant juice in raising the number of lesions when present in the inoculum may be explained by the better contact of the inoculum with the leaf surface.

Carbon in the form of lamp‐black caused an equal rise in number of lesions with purified suspensions of three viruses.

The same virus sample at a number of dilutions showed approximately equal rises in number of lesions in the presence of a uniform amount of lamp‐black. When the lamp‐black was diluted in the same ratio as the virus, the effect diminished.

The extent of the rise given by carbon was shown to be largely a function of the leaf tissues, probably of the nature of the leaf surface. Differences were observed between plants and between leaves of the same plant.
ANAEROBIC SPORE‐FORMERS IN GRASS AND GRASS SILAGE
Authors: ALLEN L. A. , HARBISON J.
Published: February 2008

The number of anaerobic spores in fresh grass appears always to be small but, in silage made from such grass, this group of organisms increases in numbers after the first few days until approximately 1,000,000 or rather more per g. are present, and these high numbers are maintained usually for several weeks. In silages made from young spring grass Clostridium sporogenes was isolated at all stages of ripening, and no other types were found in comparable numbers. In silage made from autumn grass, however, which had a considerably higher moisture content owing to inefficient drainage in the silos, and in silage made from similar grass to which various substances containing available carbohydrates had been added at the time of ensiling, strains of saccharolytic anaerobes were isolated in addition to Cl. sporogenes.
THE CHOCOLATE SPOT DISEASE OF BEANS (VICIA FABA L.) CAUSED BY BOTRYTIS CINEREA PERS
Authors: WILSON A. R.
Published: February 2008

Chocolate spot disease of broad and field beans in Britain is caused by forms of Botrytis cinerea. This disease should not be confused with the chocolate‐coloured lesions of Aphis injury, frost injury, mechanical injury, etc., and leaf spot (Cercospora Fabae and Ascochyta Fabae). All forms of Botrytis cinerea tested and some other species of Botrytis were capable of causing chocolate spot.

B. cinerea will attack other species and genera of the Leguminosae, producing in some instances lesions similar to those of chocolate spot disease of beans.

Chocolate spot infection is of two types, “aggressive”, causing blackening and death of part or the whole of the shoot system, and “non‐aggressive”, causing discrete or coalesced chocolate‐coloured lesions. The former type of attack is responsible for the greater part of the damage done by epidemics of the disease.

Under suitable environmental conditions, there is a progressive increase in the total number of visible lesions over a period of at least 5 days after treatment with a suspension of Botrytis spores. When a dilute spore suspension is used “non‐aggressive” infection occurs. When a dense suspension is used, “progressive” infection results in “aggressive” infection: if, however, plants are removed after 24 hours to an environment unsuited to infection, the attack remains “non‐aggressive”

While hyphae are abundant in the lesions of “aggressive” infection only a sparse mycelium is present in those of “non‐aggressive” infection.

The maximum temperature for infection is about 30° C, the optimum about 20° C. and the minimum between +1 and ‐1° C. A water film is essential for infection, and any factors increasing the rate of evaporation of this film inhibit or decrease infection.

The optimum conditions for “aggressive” infection are (a) the presence of large numbers of spores of the pathogen, (b) rain, (c) high humidity and rain to maintain the water film on the foliage for some days, (d) little or no wind and (e) a temperature between 15 and 20° C.

Statistical treatment of data has established a correlation between rainfall and the severity of chocolate spot disease. Epidemics are correlated with abnormally heavy rainfall during the critical months of April, May, June and July.

Spores of B. cinerea will remain viable on the leaf surface for periods of more than a month under adverse conditions.

Any factor tending to weaken the crop, such as sour soil, potash and phosphate deficiency and waterlogging of the soil, renders it more liable to “aggressive” infection. In addition, chocolate spot disease appears to be favoured by a dense stand of beans and shelter from the prevailing wind.

No economic method of control has been found. Care should, however, be taken to see that the crop is not weakened or in any way rendered more liable to attack.
THE BIOLOGY OF LEPTOBYRSA RHODODENDRI HORVATH (HEMIPTERA, TINGITIDAE), THE RHODODENDRON LACEBUG: FEEDING HABITS AND THE HISTOLOGY OF THE FEEDING LESIONS PRODUCED IN RHODODENDRON LEAVES
Authors: JOHNSON C. G.
Published: February 2008

Brief mention is made of the plants attacked by Leptobyrsa rhododendri Horv. and of the problem of immunity and susceptibility of rhododendrons to attack by the bug.

The methods and habits of feeding of L. rhododendri on rhododendrons are described. The principal feeding method consists in probing the leaf with the stylets and results in the production of a characteristic, whitish mottling on the upper leaf surface (lesion I). A less common feeding method, in which no probing occurs, often produces a brown spot (lesion II).

The character and histology of lesions I and II are described. Lesion I consists mainly of empty palisade cells with an occasional cell showing a similar reaction to saliva as cells in lesion II. Lesion II is composed mostly of unbroken cells which show a browning of the cell contents and the cell walls: apart from the change in colour, the cells in lesion II have, in sections, a normal appearance for at least 3 days after the production of the lesion. No stylet sheath is present in lesion I or lesion II. Toxic action of the saliva appears to play only a small part in the production of extensive damage, most of which results from the emptying of palisade cells (lesion I).

L. rhododendri is a mesophyll feeder and the object of the stylets is the palisade tissue of the leaf. Vascular bundles are only accidentally pierced and never become plugged as the result of salivary action.

Microchemical tests on the brown substance in lesion II are described.

Lesions very similar to lesion II can be made by scratching the surface of a rhododendron leaf with a needle. The production and spread of the brown area around a scratch is much slower than from the puncture made by a bug. The brown material in lesion II is probably produced by the oxidation of chromogens.

The lesions produced by L. rhododendri are discussed and compared with hemipterous lesions described by other workers.
THE USE OF LOGARITHMS IN THE INTERPRETATION OF CERTAIN ENTOMOLOGICAL PROBLEMS
Authors: WILLIAMS C. B.
Published: February 2008

Evidence is brought forward that in comparing the numbers of insects caught under varying conditions, with particular reference to captures in a light trap, more consistent results are obtained if the geometric means are compared than by the use of arithmetic means. This is most conveniently done by summing the logarithms of the numbers instead of the numbers themselves. If any of the numbers in the series is zero it has been found practical to add one unit to all the captures in the series and so deal with log (n+1) instead of logn.

The use of the logarithms prevents the swamping of the results in a series of observations by very high numbers on a single night. It also gives a more normal distribution of departures from a mean. As a result of the latter it is possible to apply the statistical formulae for standard deviation etc. which are not applicable to the skew curve obtained by the use of the departures of the numbers themselves from an arithmetic mean.