bluuebunny/crossref_metadata_2025 huggingface dataset:
SOIL PROTOZOA; THEIR GROWTH ON VARIOUS MEDIA
Authors: DIXON ANNIE
Published: February 2008

The protozoan population of these tobacco soils were typical species generally found in soils. No soils were free of Protozoa, though very few were found in some of the lower depth samples and in the sandy soils.

Though there was an indication that higher numbers of Protozoa were found in the chernozem soils, no definite connexion was observed between either the numbers of Protozoa or the species with the types of soil examined.

The numbers generally showed a decrease with increasing depth of soil; there were a few exceptions to this.
STUDIES IN POTATO STORAGE: INVESTIGATION OF PHYSIOLOGICAL AND CHEMICAL CHANGES DURING THE DEVELOPMENT AND RIPENING OP POTATO TUBERS
Authors: SINGH B. N. , MATHUR P. B.
Published: February 2008

Summary

An attempt is made to correlate the stage of maturity of the tubers with certain characters in the ontogeny of the vines.

Data obtained with regard to the physiological behaviour and the chemical composition of potatoes of different stages of maturity indicate the existence of three more or less distinct stages—adolescence, maturity and ripening—during the development of potato tubers.
BACTERIUM SALICIS DAY, THE CAUSE OF THE WATERMARK DISEASE OF THE CRICKET‐BAT WILLOW
Authors: DOWSON W. J.
Published: February 2008

Summary

The results of Day's original investigation of the watermark disease of the cricket‐bat willow have been, confirmed by repeated inoculations and reisolations of an organism agreeing with Bacterium salicis Day. The organism has been studied in pure culture and has been compared with a similar bacterium isolated from watermarked white willow from which it differs very slightly. The morphological, cultural and physiological characters of B. salicis are recorded and it is shown that in these respects B. salicis is closely akin to B. tracheiphilus and to a lesser degree to B. amylovorus.

A new method is described for the determination of the optimum temperature for growth based upon acid production from sucrose.

The author gratefully acknowledges his indebtedness to Prof. Brooks for his interest and helpful criticism throughout, to Mr W. R. Day for assistance in getting into touch with willow growers and to Mr J. Bryce for unstinted co‐operation in the field and for Fig. 1.
“ENATION MOSAIC” OF TOMATO CAUSED BY A VIRUS OF THE TOBACCO VIRUS 1 TYPE
Authors: AINSWORTH G. C.
Published: February 2008

Summary

“Enation mosaic” (caused by a strain of tobacco virus 1), a disease of tomato characterized by extreme leaf malformation and the development of leafy outgrowths from the undersides of deformed leaves, is described.

An account of an investigation of the effects of environmental conditions on the symptoms of enation mosaic is given and the literature is reviewed and discussed.
THE ASPARAGUS MINER (MELAN AGROMYZA SIMPLEX H. LOEW) (AGROMYZIDAE; DIPTERA)
Authors: BARNES H. F.
Published: February 2008

Summary

The history and identification of the asparagus miner. Melanagromyza simplex H. Loew, are outlined. The fly was described in 1869, and associated with asparagus in the United States of America in 1896 and 1897. In Europe it was recognized about the same date.

The salient points of the morphology of all stages are briefly described.

Its geographical range is the United States of America and Europe. In Europe it has been reported from Hungary, France, Germany and England. In U.S.A. the most numerous records are from the eastern states but it has also been reported from Iowa and California.

There are two generations a year at Harpenden, England. The flies of the first flight are on the wing from early June to the end of July, those of the second from the beginning of August until about the second week in September. Details of the life history are given.

The damage caused by the larvae mining the stems of asparagus is not considered important in cutting beds, although seedling beds might suffer more. When, however, the mining is followed by an attack by the larvae of Lonchaea flavidipennis Zett. the damage is more important.

An attempt to assess the local abundance of the flies by direct field observation is described.

Three parasites—the braconid, Dacnusa ?bathyzona Marsh.; a pteromalid, Sphegigaster sp.; and a eulophid, Pleurotropis epigonus Walk.—have been identified by Dr Ferriere and in addition an unidentified parasite has been reared. Brief observational notes have been given concerning these parasites. It is noted that Dacnusa rondanii Giard has previously been recorded as a parasite.

Control measures recommended by other workers have been mentioned.
THE HOLLYHOCK SEED MOTH (PLATYEDRA MALVELLA HÜBN.), TOGETHER WITH NOTES ON THE DISTRIBUTION OF APION RADIOLUS KIRBY AND AN ASSOCIATED GLINODIPLOSIS SPECIES
Authors: BARNES H. F.
Published: February 2008

Summary

A survey has been made of the distribution of Platyedra malvella Hübn. in Great Britain and it has been found that the larvae are restricted on hollyhock to the south‐eastern counties of England.

Apion radiolus Kirby and a gall midge Clinodiplosis species which are also found in the seed‐heads of hollyhock are generally distributed throughout England; the Clinodiplosis species also occurs in Wales and Ireland.

The life cycle of Platyedra malvella has been described. There is only one generation a year. The moths are on the wing late in June until the beginning of August. The larvae feed on the seeds of hollyhock perforating the seeds characteristically. When full grown from the middle of August onwards, the larvae descend to the soil where they spend the winter in cocoons. In May the larvae become active again and tunnel through the soil. They spin up again towards the end of May and in June for pupation. The host plants are Althaea rosea, A. officinalis and there is at least one record on cotton.
THE INSECTICIDAL PROPERTIES OF SOME EAST AFRICAN PLANTS: MUNDULEA SUBEROSA BENTH.1 PART 2, CHEMICAL CONSTITUENTS
Authors: WORSLEY R. R. le G.
Published: February 2008

Summary

A series of substances has been isolated from a sample of Mundulea bark consisting of rotenone, white crystals which are probably a mixture of l‐deguelin and tephrosin, yellow crystals which are probably dehydrorotenone, glucosides and alkaloids.

Only the rotenone is appreciably toxic to aphides.

The two sets of crystals having been obtained by use of alkali probably do not exist as such in the bark, but have been produced from a more toxic precursor, the existence of which must be assumed to account for the total toxicity of the sample.

All attempts to isolate crystals other than rotenone without using alkali have failed completely.
AN INVESTIGATION INTO THE “STRIPE” DISEASE OF NARCISSUS
Authors: CALDWELL J. , JAMES A. L.
Published: February 2008

The wide variation in appearance of infected plants gives rise to the question whether the name “Stripe” is being applied to one or more diseases. The histological bases of the various types of symptoms are described, and it is shown that they are all produced by the same three factors acting with varying degrees of relative intensity.

It is suggested that the disease is caused by a virus complex having at least three components. Inclusion bodies in the cells of diseased plants are described which resemble the X‐bodies associated with some virus diseases.

This investigation is being carried out under the auspices of the Agricultural Research Council.
INFECTION EXPERIMENTS WITH CLADOSPORIUM FULVUM COOKE AND RELATED SPECIES
Authors: BOND T. E. T.
Published: February 2008

1. Symptoms of infection on resistant and susceptible varieties of tomato (Lycopersicum esculentum Mill.) are briefly indicated, together with a numerical method of recording the progress of infection.

2. The histology of infection on tomato varieties is described. Penetration is stomatal and no appressoria or other modifications are formed. The mycelium is intercellular and without haustoria, and develops normally only for so long as the host cells are alive.

3. By the use of a controlled environment chamber, the frequency of penetration is shown to be far greater at a humidity fluctuating from saturation to 85 % than at constant saturation. The suggestion is made that penetration is controlled, in part at least, by a hydrotropic stimulus.

4. The initial rate of spread of the mycelium within the host, immediately subsequent to penetration, is lower in the variety “Mainerop” than in “Giant Red” and is lower also in the basal region of the plant than in the middle. This behaviour runs parallel with the subsequent differences observed in the external symptoms of infection.

5. Normal stomatal penetration occurs over a wide range of immune and “inappropriate” hosts.

6. Symptoms of infection have been recorded only in the varieties of L. esculentum, in L. Humboldtii Dun., and in two strains received as L. racemigerum which, appear to be more closely related to the cultivated varieties than, to the true currant tomato.

7. Confusion occurs as to the correct nomenclature of the currant tomato. The name Lycopersicum pimpinellifolium Mill, is preferred. L. racemigerum Lange (=Solanum racemigerum) and L. racemiforme Lange are synonyms.

8. The extent and distribution of the mycelium in the currant tomato appears to be determined largely by the age and relative maturity of the leaf. The mycelium is intercellular and without haustoria, and can apparently remain alive in the leaf for a considerable period of time. No conidiophores are produced. No reaction of the host cells is observed except where, on account of structural considerations, host and parasite are brought into more immediate contact. Here, individual host cells are frequently necrotic.

9. On many other Solanaceae, including species of Solatium, Hyos‐cyamus, Nicotiana, Schizanthus, and other genera, the course of events is essentially similar to that observed on the currant tomato.

10. In other Solanaceae, and in plants belonging to the Scrophu‐lariaceae, Compositae, and Cucurbitaceae, an extensive mycelium is never developed, even under apparently favourable conditions.
STUDIES OF THE MOSAIC DISEASES OF CASSAVA
Authors: STOREY H. H. , NICHOLS R. F. W.
Published: February 2008

The symptoms of mosaic disease in cassava, although generally typical of the mosaic group, show wide variations, due in part to the varietal reaction of the plant, to its stage of development and to the environment. The most important cause of variations however is differences in the strains of the virus, of which we have recognized, through the study of symptoms, two groups of severe and mild strains.

The viruses are transmitted across a graft, but we have failed to obtain mechanical transmission by needle or hypodermic injection.

A Bemisia sp. can transmit both groups of strains. It can inoculate the plant only through immature leaves, less than about one‐quarter of their full length. The virus so inoculated does not pass out of the leaf until about 8 days have elapsed. On the basis of this knowledge a convenient and reliable single‐leaf cage technique has been developed.

After the virus has entered the stem it passes rapidly to the base of this stem, but odp slowly into side branches from it or into other stems arising from the same original cutting.

Infection of a plant with a mild strain of virus failed entirely to confer immunity from infection by severe strains introduced by grafting. If the severe strains were inoculated by insects there was an indication of some conferred resistance but insufficient to make the procedure practically useful in control.
STUDIES ON APHIDES INFESTING THE POTATO CROP
Authors: DAVIES THE LATE W. MALDWYN , WHITEHEAD T.
Published: February 2008

Summary

The investigations were planned to ascertain the extent of the migrations of Winged aphides, their ability to detect individual plants, the development of aphis population following colonization, and the extent to which Virus diseases may be transmitted to isolated plants by winged aphides.

Plants were isolated in root crops on seven farms and at varying distances from probable sources of virus infection. Four farms were located in districts where aphis population is usually high and viruses spread very rapidly; two in districts where both aphides and spread of viruses are minimal, whilst one farm could be regarded as intermediate in both respects.

Evidence is submitted to show that winged aphides have no difficulty in detecting and colonizing isolated plants. Their numbers were large at the four eastern centres and very small at the three western centres. In all cases the aphis population on isolated plants was less than that of the nearest general crop and suffered more from predators and parasites.

It is shown that isolated plants can be reached by migrants from a distance of at least a quarter of a mile, and probably much further. Additional evidence is given that these initial migrants introduce little virus infection to potato crops from extraneous sources. The importance, however, of the later movements of winged aphides, whether initial migrants or those subsequently produced on potatoes, in spreading Viruses from crop to crop, is emphasized.

The practical aspects of protecting potato stocks is discussed under conditions of (a) heavy infestation by winged aphides and proximity of partially diseased crops; (b) minimal winged aphis infeatation where numerous sources of virus infection occur in neighbouring crops; and (c) where both aphis infestation and sources of infection are minimal. It is considered that regulations for the improvement of health in seed‐potato stocks should take cognisance of these various possibilities.
THE VIABILITY OF WEED SEEDS AT VARIOUS STAGES OF MATURITY
Authors: GILL N. T.
Published: February 2008

Summary

Certain plants within the family Compositae wher cut lown in the flowering condition produce viable seeds; others do not. The first group includes: Sonchus oleraceus, Senecio Jacobaea, S. vulgaris and Aster Tripolium, whilst the second group includes: Taraxcum vulgare, Hypochaeris radicata, Cirsium arvense and C. lanceolatum.

Certain species in other families produce viable seeds when cut down at various stages of maturation of the fruits following fertilization.

When the mature seeds exhibit a prolonged dormant period, the seeds harvested in an immature state exhibit a similar period of dormancy.

In Papaver dubium and Datura stramonium, the immature seed germinated more readily than the fully ripened seed, owing to the impermeability of the seed coat of the latter.

A combination of fluctuating temperature and illumination improved the germination of the two Rumex species when tested soon after harvesting, but had no effect on other species found difficult to germinate in an incubator at constant temperature. Three months after harvesting of the Rumex species the seeds germinated equally well in the incubator at constant temperature.
THE ECOLOGY OF THE LARGER FUNGI
Authors: WILKINS W. H. , HARLEY J. L. , KENT G. C.
Published: February 2008

Summary

The paper is the second of a series which is dealing with investigations into the ecology of the larger fungi.

It represents a somewhat detailed examination of the fungus flora of a plateau beech wood in relation to (a) vegetation and (b) substrate.

In the first case, distribution of fungi in the three subtypes—No field layer, Oxalis societies and Mercurialis societiesis recorded and discussed.

The second section deals with distribution in relation to soil types, humus and leaf litter, with notes on hydrogen‐ion concentration.

There is a brief discussion of results.
SOME SPECIES OF PYTHIUM PARASITIC ON WHEAT IN CANADA AND ENGLAND1
Authors: VANTERPOOL T. C.
Published: February 2008

Summary

The results of a comparative study of six species of Pythium pathogenic to wheat seedlings are presented. P. arrhenomnes, P. volutum, and P. tardicrescens n.sp., were found in both Canada and England; or, for P. graminicolum and P. torulosum [?] in England and not in Canada; and P. aristosporum. n.sp., only in Canada. The English forms were obtained from Bucks, Cambs, Kent, Herts, Berks, and Lincs, and the Canadian forms from Saskatchewan. The similarity of the English form considered as a geographic strain of P. torulosum with the form reported on wheat in Italy by Petri is pointed out. Attention is drawn to the wide geographic distribution of species of Pythium on graminaceous hosts. By the method of isolation used, it was relatively easy to obtain one or more of these fungi either from wheat seedlings grown in potted soil collected at random from virtually any field with cereals in the rotation, or from seedlings collected from the poorer looking parts of such fields. All of the parasitic species isolated belong to the group of the genus with lobulate sporangia. It is suggested that the many sphaerosporangial forms encountered may render the wheat seedlings more liable to attack by the pathogenic forms themselves. The use of fertilizers may prove beneficial.
FURTHER OBSERVATIONS OF THE INCIDENCE OF BLOTCHY RIPENING OF THE TOMATO
Authors: WHITE H. L.
Published: February 2008

Summary

The annual fluctuation in percentage o‐f fruit affected with “blotchy ripening” on potassium‐deficient and nitrogendeficient plots at the Cheshunt Experimental Station is significantly negatively correlated with the mean daily number of hours of bright sunshine between 1 April and 31 August.

The weight of fruit of potassium‐deficient plants is raised and the percentage of blotchy fruit reduced, either by increase of potassium supply or by increase of light. This beneficial effect of increase of light on the crop of potassium‐deficient plants is of much greater magnitude than any corresponding effect on the crop of nitrogen‐deficient or completely manured plants.

The juice of the blotchy areas of potassium‐starved fruits has diminished capacity for starch hydrolysis.

Increasing severity of potassium starvation is associated with progressive increase in level of dry weight per unit area of the leaves.

The influence of potassium on the production of blotchy fruit is briefly discussed.
SHEEP BLOW‐FLY INVESTIGATIONS
Authors: HOBSON R. P.
Published: February 2008

Summary

An investigation has been made of the effect of temperature upon the time required for the development of the ovaries in the sheep maggot fly.

It has been shown that two meat meals are essential for the development of mature eggs in the ovaries. This applies also to the further production of eggs after opposition.

Neither plant materials nor animal excreta can replace meat in the diet of the female fly if eggs are to develop in the ovaries.

Various products of putrehction stimulate gravid females to opposite, but these substances do not attract flies from a distance.
THE MANURIAL REQUIREMENTS OE PYRETHRUM (CHRYSANTHEMUM CINERARIAEFOLIUM TREV.)
Authors: MARTIN J. T. , MANN H. H. , TATTERSFIELD F.
Published: February 2008

Summary

A small field experiment upon the manurial requirements of the insecticidal pyrethrum plant, grown upon sandy soil of low fertility, is described. Lime had the effect of producing slight, but not significant, increases each year in the yield of flowers and their content of the pyrethrins, and decreased the percentages of plant failures in the fourth and fifth years of the experiment. There was a significant depression in the yield of flowers in the year after the single application of double dressings of the manures, but no effect in later years. The yearly application of moderate dressings of manures gave significant increases in the yield of flowers in the second and fifth years, and significant increases in the pyrethrin I content of the flowers in the fourth and fifth years of the experiment.
STUDIES ON PUCCINIA ANOMALA ROST.
Authors: N‘OLIVBIRA BRANQUINHO
Published: February 2008

Summary

Methods of establishing pure cultures of rusts are discussed and a new spore‐proof and insect‐proof cellophane cylinder is described.

Eighty‐two cultures, isolated from collections of P. anomala in Great Britain, Portugal and Spain, have been tested for the determination of physiologic races. The barleys used as differential hosts were those used by Hey and Mains and also Aegyptische 4‐zeilige Sommergerste. Eleven new physiologic races have been identified and are numbered 12–22. Race 12 was found to be widely distributed in Great Britain, Portugal and Spain, the other ten were localized. Races 13, 14, 15 and probably 18 were found in Britain, races 18, 19 and 20 in Portugal, and races 16, 17, 21 and 22 in Spain.

A mutant, differing in colour (orange and yellow) and in pathogenicity, is recorded for P. anomala. The mutant arose from an unstable culture of race 14 cultivated on Hordeum vulgare pallidum (Sudan), and is numbered physiologic race 23.

Segregation and hybridization of physiologic races occurred through the aecidial stage on Ornithogalum umbellatum L. The heterozygous condition of physiologic races 12, 13 and 23 was demonstrated. Self‐fertilized material from race 12 gave rise to the parent race, to races 16 (?) and 19 and to four new races described under the numbers 24, 25, 26 and 27. From self‐fertilized material of race 13, races 12(?), 13, 22 and 24 were isolated and also two new races numbered 28 and 29. From self‐fertilized material of race 23, races 12, 19, 20 and 22 were isolated. A reciprocal cross between physiologic races 13 and 23 was achieved; in one direction the progeny gave rise to a single physiologic race, which proved to be new and is numbered 30; in the other direction the two physiologic races 30 and 18 were produced. This result is discussed and is attributed to cytoplasmic inheritance.

Several biotypes of physiologic races 12 and 13 were found; they seem to establish a linkage between the two races.

A new selection of differential hosts for the differentiation of physiologic races of P. anomala on cultivated barleys is proposed. A “Numerical Table” of the thirty physiologic races and an “Analytical Key” for their determination are given.

The distribution of physiologic races of P. anomala on cultivated barleys in Great Britain, Portugal and Spain is discussed.

From field observations it is concluded that at Cambridge P. anomala may overwinter in its uredospore stage. Evidence is given that in Portugal the uredospores survive the summer in the mountains.
STUDIES ON APHIDES INFESTING THE POTATO CROP
Authors: DAVIES W. MALDWYN , Whitehead T.
Published: February 2008

Summary

This communication is the substance of a report on a survey of the aphis population in certain districts of Scotland carried out from 24 July to 4 August 1936.

Forty‐three centres in eastern Scotland, from Midlothian in the south to Ross‐shire in the north, were examined by the standard method for determining the aphis “index” figure.

The varying figures obtained have been analysed with a view to establishing any relation there might be with (a) proximity to winter host plants, and (b) meteorological conditions such as temperature, humidity and wind velocity.

The results have been summarized in a discussion in which are indicated the special precautions necessary to ensure health in seed‐potato stocks.
THE ASSOCIATION OF APPLIED BIOLOGISTS AND THE ANNALS OF APPLIED BIOLOGY— A RETROSPECT (1904‐38)
Authors: BRIERLEY WILLIAM B.
Published: February 2008

With the close of 1938 the Annals of Applied Biology completed its first 25 volumes, and the occasion appeared to be a suitable one on which to review progress in the Association and its journal.

I am indebted to various senior Members who read this account in typescript and pave me the benefit of their greater knowledge and experience.
A STUDY OF CERTAIN SPECIES OF THE GENUS SCLEROTINIA
Authors: KEAY MARGARET A.
Published: February 2008

Investigations were carried out on Schrotinia serica, two strains of S. Sclerotiorum de Bary, five strains of S. Trifoliorum Eriks., two forms of S. minor Jagger, four isolations of a Sclerotinia from Vicia Faba considered to be a variety of Sclerotinia Trifoliorum, and a variant which arose from one of these isolations.

Their pathogenicity to several different plants was tested and the fungi were found to fall into three groups: (1) S. Sclerotiorum and S. minor, (2) S. Trifoliorum and its variety Fabae, and (3) S. serica.

A variant with light brown sclerotia which arose from S. Trifoliorum var. Fabae differed from the parent form in pathogenicity.

Ascospores of S. Sclerotiorum, S. minor and S. Trifoliorum did not infect healthy leaves.

The production of mycelium by sclerotia in the soil was not observed.

S. serica differed from the other fungi in that it produced numerous apothecial stipes and several apothecia in test‐tube cultures.

Exposing sclerotia to different conditions of temperature and moisture after their removal from culture and before their burial in damp sand did not hasten apothecial production.

Sclerotia formed in cultures grown over a wide temperature range produced apothecia when subsequently buried in damp sand.

Single‐spore lines of S. serica, S. Sclerotiorum, S. minor and S. Trifoliorum produced apothecia.

Apothecial production took place over a wide temperature range.

Apothecia of one form of S. minor arising from sclerotia formed on sterilized vegetables were larger than those from sclerotia formed on malt‐extract. The dimensions of the apothecia are given and a description of the apothecia of S. Sclerotiorum, S. minor, S. Trifoliorum and S. Trifoliorum var. Fabae.

Measurements are given of asci and ascospores.

The minimum, maximum and optimum temperatures fpr linear spread of mycelium are given: also the time taken by cultures to reach a diameter of 6 cm. at 207deg;C. The view is expressed that such data should not be used for differentiating species. S. serica spread more slowly than the other species. The variant of S. Trifoliorum var. Fabae had different temperature relations from the parent form.

A brief description is given of the cultural appearance of S. Sclerotiorum, S. Trifoliorum, S. minor, S. Trifoliorum var. Fabae and its variant.

The classification of the fungi is discussed.
A COMPARISON OF THE METABOLISM OF MOSAIC DISEASED POTATOES WITH THAT OF NORMAL POTATOES
Authors: COCKERHAM GEORGE
Published: February 2008

Summary

The effects of potato virus X upon the carbohydrate and total nitrogen contents of potato leaves have been followed over diurnal and seasonal periods in the varieties President and Arran Victory.

The gross metabolism of carbohydrates has been found to be similar in both mosaic‐diseased and normal leaves.

Three major trends of carbohydrate metabolism, each of which may be identified with a particular stage of leaf development, have been recognized and discussed.

Slight modifications of the fundamental metabolism of diseased leaves have been found in a reduced photosynthetic activity, disturbed starch‐sugar relationships, and an impediment in translocation during the pre‐senescent stage. All these have been ascribed to secondary effects arising out of the pathological change brought about as a result of virus infection.

Transient modifications in carbohydrate metabolism have been traced to prematurely retarded growth activities leading to a diminished demand for carbohydrate in support of growth in the diseased plants.

A significantly greater content of nitrogen has been found in diseased leaves at all stages of growth, and it has been suggested that the pathological symptoms and prematurely retarded growth activities which give rise to disturbances in carbohydrate metabolism are direct manifestations of a disorganized nitrogen metabolism.
PHYTOPHTHORA ERYTHROSEPTICA PETHYBR. IN RELATION TO ITS ENVIRONMENT
Authors: CAIRNS H. , MUSKETT A. E.
Published: February 2008

Summary

The present contribution, as part of a general study of pink rot of the potato, deals with Phytophthora erythroseptica Pethybr. in its relation to staling, light, acidity, moisture and temperature.

In natural media the fungus is not, or but very slightly, affected by its own staling products, but, in general, is intensely intolerant to the presence of other fungi and bacteria.

Ordinary daylight is not concerned in the growth or reproduction of the fungus.

Growth occurs over a wide pH range (3·2 to circa 9·0–10·0); sexual reproduction occurs over this range except towards the limits of acidity and alkalinity; asexual reproduction was not investigated experimentally. It is considered that modification of the soil reaction, within practical limits, does not offer a means for control of the disease.

The moisture factor controls directly the incidence of the disease in contaminated soil—with low moisture infection is inhibited; with normal moisture infection occurs via the dead or moribund stolon through the “heel” of the tuber; with high moisture the tuber is infected directly in the region of an “eye”. Sporangia are only formed under aquatic conditions and it is considered probable that “eye” infection is brought about through the agency of zoospores.

The temperature limits of growth are 0–32°C. with an optimum at 25°C. Oospore production occurs only between the optimum and minimum growth temperatures (0–25°C), being inhibited above the growth optimum. Asexual reproduction seems to be similarly related to temperature.
FACTORS AFFECTING THE RESISTANCE OF THE FLOUR BEETLE, TRIBOLIUM CONFUSUM DUV., TO HYDROGEN CYANIDE1
Authors: GOUGH H. C.
Published: February 2008

Summary

Two types of apparatus for exposing insects to known concentrations of toxic gases, under controlled conditions, were constructed and are described.

The relative resistance of different stages of the flour beetle, Tribolium confusum Duv., to hydrogen cyanide was determined, the results being treated by Bliss's method. The order of resistance was pupa (most resistant), adult, larva, egg. The difference in resistance at different ages was found for the pupa, adult and egg. The application to all these results of Cotton's theory of the relation of rate of metabolism and susceptibility to fumigants is discussed. It is considered that this theory might hold for stages other than the egg.

A series of experiments was carried out to discover whether individual resistance to hydrogen cyanide was inherited. It was found that the offspring of resistant individuals were significantly more resistant than the offspring of susceptible individuals, and that this difference was maintained over several generations.

A considerable increase in resistance was found to occur if adult beetles were removed from their flour about an hour, instead of immediately, prior to their fumigation. The reason for this increase was not determined, but various suggestions to account for it are discussed.

It was noted that under certain conditions, adult beetles emitted a volatile substance which was self‐toxic, and also appeared to react with cyanide.

The dosage‐mortality curves for all the experiments are discussed and possible reasons for their apparent abnormality put forward.

The experiments here described, which must only be regarded as preliminary, emphasize

The complexity of the problems arising in the study of the resistance of living organisms to toxic substances.

The need for carrying out such experiments under as natural conditions as possible.

The importance of a careful analysis of factors which affect the resistance of the organism.
STUDIES UPON THE TIME OF FLOWERING OF PLANTS: ANATOMICAL, FLORISTIC AND PHENOLOGICAL ASPECTS OP THE PROBLEM
Authors: GRAINGER JOHN
Published: February 2008

Summary

The growing points of more than 100 plant species of diverse habit have been examined between 1937 and 1939, in order to find the exact times of flower initiation.

Types of organization for flowering may be classified into (a) direct‐flowering plants, (b) indirect‐flowering plants, (c) cumulative‐flowering plants and (d) climax flowering plants. Initiation of the flower in (a), (b) and (c) may either begin (i) during the period of maximum vegetative growth or (ii) when vegetative growth is at a minimum. In the latter class, any direct cause of flowering operated entirely or largely by external influences, such as those affecting the vigour of photosynthesis, would appear to be eliminated.

Abnormal flowering of some indirect‐flowering plants during the autumn of 1938 suggests that their physiological rest periods were concluded at that time. Their normal extension of dormancy until the following spring is probably a direct effect of winter climate.

Plant habit, as annual, biennial, perennial, does not appear to affect the time of flowering, unless associated with a store of food, but not all plants with stored food flower early.

A series of correlation diagrams of the two variables, temperature and time of flowering, has been prepared from the Royal Meteorological Society's phenological data. These suggest that temperatures before the initiation of flower bud formation, in addition to those at other periods of floral development, may affect the time of flowering. Some species appear to be hastened by higher temperatures than normal at this period, e.g. ivy, and yet other kinds by temperatures lower than normal, e.g. coltsfoot.

Flower emergence in thirteen wild plants is hastened by a temperature higher than that of normal climate for a period just before the time of opening.
INTRANUCLEAR INCLUSIONS IN VIRUS INFECTED PLANTS
Authors: KASSANIS BASILIOS
Published: February 2008

Summary

Two kinds of intracellular inclusions in solanaceous plants infected with severe etch virus are described. One occurs in the cytoplasm and is similar to the X‐bodies found in many other plant virus diseases. The other occurs only in the nuclei. These intranuclear inclusions appear to be crystalline, have the form of thin rectangular plates, and resemble the inclusions described in the polyhedral disease of silkworms more than any other type of previously recognized virus‐inclusion.
THE MORPHOLOGY AND BIOLOGY OF THE BRAMBLE SHOOT‐WEBBER, NOTOCELIA UDDMANNIANA L. (TORTRICIDAE)
Authors: DICKER G. H. L.
Published: February 2008

Summary

A detailed study of the morphology and biology of all stages in the life cycle of Notocelia uddmanniana L. has been made over a period of 2 1/2 years.

This tortricid is a pest of loganberry in certain fruit‐growing areas.

The widths of the head capsules in all larval instars have been measured and found to follow Dyar's Law.

In the East Mailing district an ichneumonid, Omorgus mutabilis H.Gr., parasitizes 35–50 % of the larvae. A few specimens of an undescribed species of Apanteles have been bred from larvae, and also a tachinid fly, Nenwrilla notabilis Mg.

Preliminary control measures have given poor results.
ON THE LIFE‐HISTORY AND ECOLOGY OF LUMBRICILLUS LINEATUS MULL. (OLIGOCHAETA)
Authors: REYNOLDSON T. B.
Published: February 2008

Summary

A survey of the natural and artificial habitats of Lumbricillus lineatus Mull, shows a wide range and toleration of diverse chemical conditions.

The bacteria beds are described in relation to the needs of the worm.

An account is given of the life‐history of the worm including breeding season, copulation, cocoon deposition, development and hatching. The latter is given in detail since it is believed to be new. It demonstrates a use of the eversible pharyngeal plate. Experiments show that the hatching worms increase in size with an increase in quantity of food available within the cocoon in the form of undeveloped ova.

A short account of the parasites and possible predators is given.

Experiment shows that the worms migrate from low temperatures to higher, a reaction observed in the beds during cold weather.

Temperatures below 6°C. affect adversely: (a) cocoon deposition, (b) rate of development, (c) hatching. The beds, in contrast to natural habitats, rarely fall below 6°C. Egg sterility is increased at a temperature of 20°C.

The bacteria beds form an environment for this worm which includes all the main features of its natural habitats. The higher temperature in winter, the protection from desiccation and birds, and the scarcity of natural predators allow excessive multiplication of the worm. Further, certain factors in the beds, probably the peculiar chemical conditions, prevent colonization by other similar worms so that competition with other Oligochaetes is at a minimum. Thus, by virtue of its great degree of physiological adaptability, this worm is able to thrive in the bacteria beds to an extent not found in any natural habitat.
NOTE ON THE LIMITATION OF INFECTION OF WHEAT BY ASCOSPORES OF OPHIOBOLUS GRAMINIS SAAC. A POSSIBLE EXPLANATION
Authors: PADWICK G. WATTS
Published: February 2008

Single spore cultures of O. graminis Sacc. produced ascospores on the host, confirming the conclusion of Davis (1925) that the fungus is homothallic.

Single spores removed from a Petri dish took several weeks to germinate, whereas the spores remaining in the dishes germinated within 24 hr.

It is suggested that a retardation of spore germination may have been due to dilution of some necessary chemical substance.

The significance of slow spore germination in relation to the results obtained by Garrett (1939) on infection of wheat seedlings by the ascospores of O. graminis is discussed.
AEROBIC DENITRIFICATION
Authors: Meiklejohn Jane
Published: February 2008

DENITRIFICAITION is the reduction of nitrates to gaseous nitrogen, sometimes mixed with oxides of nitrogen: it is the only process which certainly causes a loss of nitrogen in nature, because the nitrogen gas escapes into the atmosphere. It is known that nitrite certainly, and probably hyponitrite, are formed as intermediates in the course of the reaction; it is obvious that nitrate (or nitrite) must be present if denitrification is to take place; and it is also known that a compound to act as a hydrogen donator is necessary for the process. Karlsen (1938) published a detailed study of the effect of pH and of iron on denitrification by Pseudomonas aeruginosa; and Elema (1932) and Elemaet al. (1934) studied the changes in oxidation‐reduction potential during denitrification by Micrococcus denitrificans. Elema's paper includes a set of equations which represents the most probable course of the reaction.

Several details of the process remain obscure, among them being the effect of aeration. The generally accepted view is that denitrification is an essentially anaerobic process, and that it is diminished or stopped by the admission of air. This supposition is probably accepted mainly because it provides a neat teleological explanation for the fact of denitrification; oxygen is made available by the reduction of nitrate; so under anaerobic conditions the bacteria reduce the nitrate in order to supply themselves with oxygen. Under aerobic conditions they need not reduce nitrate to obtain oxygen, and it is therefore assumed that they do not reduce it. This supposition is based on very little experimental evidence; though Weissenberg (1902) described a strain of Pseudomonas aerugimsa, which grew on nitrite under aerobic conditions, but did not reduce it, while in anaerobic cultures the nitrite was all reduced with much gas production. There is no reason to suppose, however, that every denitrifying species is affected by aeration in the same way. Seiser & Walz (1925) found that nitrogen was lost from both aerobic and anaerobic cultures of Ps. putida. The effect of aeration on Ps. deniirofIuolescetrs was studied by Korochkina (1936), who remarks “a relatively high rH value does not exclude denitrification. Therefore it is very difficult to eliminate denitrification by means of increased aeration.”

The experiments described in the present paper were mainly concerned with the effect of aeration on denitrification; they were performed with pure cultures of two denitrifying species in simple synthetic liquid media.
The resistance of potato varieties to Heterodera schachtii Schmidt, the potato‐root eelworm
Authors: Gemmell Alan R.
Published: February 2008

The potato varieties Epicure and Doon Star permitted the production of fewer and smaller cysts of Heterodera schachtii on their roots than the varieties Golden Wonder and Majestic, when all were grown under standard conditions. Under the stimulus of potato‐root excretion the number of larvae which emerged from Epicure and Doon Star cysts was less than that from Majestic or Golden Wonder cysts of the same volume. Accepting Lapage's (1938) criteria of resistance to nematode infestation in animals and applying them to plants, it is concluded that this deleterious effect of the variety on the eelworm is probably of the nature of a degree of resistance to eelworm attack specific to each variety and is physiological and not anatomical in action. Of the varieties tested, Epicure is judged the most resistant, closely followed by Doon Star. Majestic is fairly susceptible but not so much so as Golden Wonder on which the eelworm forms large cysts that are extremely productive of larvae.
The moisture content of timber in relation to attack by Lyctus powder‐post beetles
Authors: Parkin E. A.
Published: February 2008

The relation between moisture content of oak sapwood and rate of development of Lyctus brunneus has been investigated at 23d̀C. Oviposition took place normally in samples of various moisture contents between 5.5 and 23.5%. The eggs hatched in wood of 7.7% moisture content, but not of 61% moisture content, although the embryos developed fully. The rate of gain in weight of young larvae increased to a maximum as the moisture content of the wood rose to about 14.2% and then fell again. The rate of development from egg to adult followed a somewhat similar curve with a maximum at 16% moisture content. At all moisture contents the first male emerged a few days earlier than the first female. The average weight of the male beetles was less and their moisture content greater than those of the corresponding females. The average weight of the beetles showed a tendency to increase at moisture contents of the wood above 97%. The average moisture content of the males was fairly constant up to 156% moisture content of the wood, but that of the females rose slowly as the moisture content of the samples increased. In wood of 15.6% moisture content at 23d̀C. the minimum period of development from egg to adult was 167 days; at 14.2% moisture content and 27.5d̀ C. this was reduced to 142 days. Green timber was shown to be liable to infestation as soon as a superficial skin was formed of a suitable moisture content; the upper limiting moisture content is probably the fibre saturation point. Control of moisture content of timber cannot be achieved sufficiently easily for it to become an important method for the control of Lyctus infestation.
Field studies of potato‐root eelworm, Heterodera rostochiensis Wollenweber, 1938‐40
Authors: Miles H. W. , Henderson V. E. , Miles M.
Published: February 2008

Field studies of potato crops under different soil and fertility conditions and exposed to attack by diverse concentrations of potato‐root eelworm led to the following conclusions:

In the north‐western agricultural advisory province potato‐root eelworm is not a major cause of failure or partial failure of potato crops on land where the viable cyst concentration is low (under 10/10 c.c. of soil). On such land increased yields can be obtained by improving conditions for plant growth, widening the rotation and increasing the fertility of the soil.

The production of satisfactory crops on land with a low eelworm population is likely to be accompanied by considerable increases in the numbers of root eelworms in the soil.

Crops free from signs of ‘potato sickness’ or ‘potato‐root eelworm disease’ can be grown on land heavily infested with root eelworms (viable cyst concentration exceeding 25/10 c.c.), if no other adverse condition, such as unsuitable weather, lack of available food or incidence of fungus disease, affects the growth of the crop, but yields from heavily infested land are not likely to be more than moderate.

The treatments used against eelworms in the trials described here did not give results commensurate with their cost.

The practical difficulties of incorporating lethal substances with soil in the field are considerable, and this may have contributed to the disappointing results obtained.

The study of the influence of host variety on cyst production suggests that varietal differences in the host plants may influence the numbers of cysts formed on the crop, but the evidence is not conclusive.
The depletion of starch from the sapwood of the ash (Fraxinus excelsior) and its relation to attack by powder‐post beetles (Lyctus spp.)
Authors: Henderson F. Y.
Published: February 2008

The depletion of starch in the living sapwood of ash was examined as a possible means of rendering converted timber immune from attack by Lyctus (powder‐post beetle).

Observations on disks of timber kept under controlled conditions showed that depletion is conditioned by access of oxygen; thus although in the standing tree depletion proceeds from without inwards, it can be induced in any part of the sapwood, and in any direction, by permitting access of oxygen, i.e. there is no polarity in depletion. The optimum temperature range for depletion in ash is from 31 to 36d̀ C.: above 45d̀ C. death of the cells may interrupt depletion.

The presence of β‐indoly acetic acid does not influence rate of depletion. Reformation of the starch in the depleted wood in the presence of cane sugar could not be induced. The enzyme concerned in mobilization of the starch appears to be a labile one with an optimum in the neighbourhood of 40d̀ C. and to be produced during the active respiration of the cells, starch depletion ceasing when oxygen is withdrawn.

In transversely cut disks the rate of respiration at 33d̀ C. ceases to be proportional to the volume of tissue after a thickness of about 6 mm. has been attained. At 20d̀ C. disks 10 mm. thick may be evenly depleted. Infestation experiments upon timber undergoing depletion showed that the attack by Lyctus is circumscribed by starch‐level and not by total nitrogen or soluble sugars.

Under correct conditions of kilning, 1 in. sapwood plank can be rendered starch‐free in about 20 days: with larger sizes depletion is uncertain and probably uneconomic.

The methods of starch and sugar analysis used in the work are appended.
Studies in the physiology of the onion plant
Authors: Heath O. V. S.
Published: February 2008

The investigation concerns the effects of five factors upon the tendency of onion sets to bolt and the production and ripening of bulbs. The factors studied fall into three categories: (1) conditions under which seedlings were grown to produce sets, (2) conditions of storage of sets during dormancy, (3) conditions of growth during the second season. The first comprised sowing date of seed (day‐length and temperature effects) and temperature of growth while forming sets; the second, high‐and low‐temperature storage for different periods and throughout the winter; the third, temperature and day length during the second season. Field trials and experiments with controlled environment were carried out. The main results of the former were as follows: Large sets were much more liable to bolting than small. Sets produced at high temperature under glass were practically free from bolting when grown on, irrespective of the storage conditions. Storage throughout the winter (22 weeks) at 30d̀ C. practically eliminated bolting; 30d̀ C. for the first 8 weeks reduced bolting but given for the last 8 weeks was much less effective. Cold storage (od̀ C.) throughout or for the first 8 weeks considerably reduced bolting, but when given for the last 8 weeks tended towards increase. High‐temperature storage leads to loss in weight; the maximum loss in any treatment, 75%, was associated with 77% mortality in the field. This detrimental effect on survival is confined to sets produced at high temperature (which require no heat treatment as they have no tendency to bolt), while sets produced at lower temperatures show no high mortality during or after high‐temperature storage. The reduction in bolting following high‐temperature storage is not due to water loss by the sets. High temperature of storage throughout or for the last 8 weeks delayed ripening of the bulbs, and resulted in larger yields; no such effect was obtained by high‐temperature storage during the first 8 weeks.