bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Potato Virus Diseases: IX. Some Further Experiments ON THE Insect Transmission OF Potato Leaf‐Roll
Authors: Smith Kenneth M. 
Published: February 2008

Summary.

Experiments bearing on a possible relationship between the leaf‐roll virus and the aphis vector, M. persicae Sulz., are described. The following facts are elucidated by the experiments:

The non‐infective aphis can pick up the virus of leaf‐roll from an infected potato plant after 6 hours' feeding.
The infective aphis is capable of transmitting the leaf‐roll virus to a healthy potato plant after 2 hours' feeding.
The whole process whereby a non‐infective aphis picks up the leaf‐roll virus and infects a healthy plant cannot be performed in 8 hours; a minimum period of approximately 54 hours appears to be necessary.
The incubation period of the leaf‐roll vim in the potato plant, i.e. from the time of infection to the time of the appearance of first symptoms, averages 14 days under the Writer's conditions.

It has not been found possible to infect healthy potato plants with leaf‐roll by needle inoculation with the body juices of infective aphides.
Infection of progressive series of healthy potato plants with virus‐bearing M. persicae showed that the aphides were capable of infecting respectively 6, 7 and 10 healthy potato plants without again having access to a source of leaf‐roll infection. It is noteworthy that occasionally plants in the progressive series of infections failed to develop leaf‐roll, although plants before and after in the series became infected.
The leaf‐roll virus occurring in American potato varieties as exemplified by “Green Mountain,” is as easily disseminated by the aphis M. persicae as the leaf‐roll virus occurring in the British Isles.
Further inoculation tests with five additional species of aphides are described; of these five aphides, two were proved to be capable of transmitting the virus of potato leaf‐roll. These are the potato aphis, M. pseudosolani Theob. and the greenhouse aphis, M. circumfixus Buckt. Negative results were obtained with two other potato aphides, i.e. Macrosiphum gei Koch and A. rhamni Boyer, and one greenhouse apliis A. gossypi Glover.
Illustrations are given of the four chief potato‐feeding aphides in England, together with the greenhouse aphis Myzus circumflexus, which has been proved capable of transmitting leaf‐roll. The chief diagnostic characters of these five aphides are indicated.
Yield Studies in Oats: IV The Influence of Climatic Factors Upon the Growth of A Spring Sown Variety “Record”
Authors: Tincker M. A. H. , Jones Martin G. 
Published: February 2008

Summary.Previously reported studies with oats have been continued. The present paper deals with the rate of growth of the plants in the field in relation to the meteorological conditions experienced in mid Wales. The method employed was to lift plants at weekly intervals and to measure the leaf area and obtain the dry weight of the top growth.1. It has been shown that the Unit Leaf Rate (measured on the “tops” of the plants only) is correlated with the previous rainfall and also with the temperature, during that period of growth in which the plants are forming new leaves and increasing their leaf area.2. The relative rate at which the leaf are& increased is correlated also with the previous rainfall; high rainfall ensures leaf development. The rate at which the area increases was negatively correlated with temperature under the field conditions. That is to say that the plant is a cool‐loving cereal.3. When the relative rate at which the dry weight of the tops increased was employed as the index of growth it was not possible to trace out significant relationships with the meteorological data.4. A comparison with the correlation studies of other workers is also made. Some of the limitations of the method are pointed out, and brief reference to previous criticisms of similar methods employed by other investigators is made. The method has been shown to provide data of a reliable kind, in the case of field grown plants. Previously no such field studies with our common crops had been made.
The Physiology of Virus Diseases in Plants: II. Further Studies on the movement of mosaic in the Tomato Plant1
Authors: Caldwell John 
Published: February 2008

Summary.In this paper the results of some experiments with aucuba mosaic in tomato are discussed. These results support the general thesis that the agent does not normally travel in the xylem stream. The movement of tobacco mosaic in tobacco and in tomato was found to be similar to that of aucuba mosaic. The majority of the experiments were carried out with aucuba mosaic in tomato.It was found that filtered virus juice from virus‐infected plants was readily absorbed at the cut end of a petiole and thence travelled into the xylem of the main stem. The removal of the treated petiole within 48 hours prevented infection taking place. On the other hand, when the petiole was left attached the experimental plant developed symptoms in the usual manner. This type of experiment was repeated with the exception that, after the removal of the treated petiole, the leaves above were crushed. Infection of the plant followed this treatment. This experiment was combined with the earlier experiments in which the living tissue of an internode was killed by steam. The agent was found to be carried mechanically in the xylem across the dead tissue.As a consequence of this observation the experiments with plants with “steamed” internodes were repeated. It was found that in no caw did crushing of the leaves induce symptoms on the upper part of the plant when inoculation had been made on the lower side of the “steamed” internode.It was concluded that the virus agent did not normally enter the water stream, and when it was introduced experimentally into it. though it was carried round, there was no mechanism by which it could leave the vessels.The absence of the agent from the hydathode exude was demonstrated.Apparently the agent cannot enter an unbroken cell, nor can it move through or out of dead cells. It has been found that great care must be taken to ensure the absence of traces of toxic substances from inocula to be tested, otherwise infection may not take place even in the presence of the agent itself.The rates of movement of the virus agent in the tomato are practically the same upward or downward. The slightly greater rate of upward movement appears to be associated with the greater metabolic activity which occurs in the upper portion of the plant. The movement of the virus agent along the protoplasmic strands has been examined by inoculating plants with infective juice after the removal of large portions of the vascular tissue. This treatment does not appear to delay the movement of the agent up the stem.In a final group of experiments, darkness did not appear to have any effect on the multiplication of the virus in the tissues. Too prolonged periods in the dark, however, caused the permanent wilting of both diseased and healthy plants. This “wilting” is considered us In‐mir due to the respiration of carbohydrates, etc., and the earlier collapse of the diseased plants as being due to a smaller carbohydrate supply in them.This work was carried out under the auspices of the Empire Marketing Board.
ON the Transmission of Potato Leaf‐Roll by Aphides
Authors: Whitehead T. 
Published: February 2008

Summary.1. Evidence is submitted to show that Myzus circumflexus (Buckton) is as efficient a vector of potato leaf‐roll as is Myzus persicae (Sulz). The implications, both practical and academic, of this fact are discussed, particularly in view of the retardation in the development of symptoms shown by plants infested with Myzus circumflexus carrying the leaf‐roll virus.2. Macrosiphum gei (Koch) only transmitted the disease once and its importance as a field vector is still an open question.The writer is glad to acknowledge the help given by the laboratory assistant, Mr G. L. Turner, in the above work.
Experiments on the Control of Tomato Leaf Mould (Cladosporium Fulvum) By Fungicides and Fumigants
Authors: Small T. 
Published: February 2008

Summary.1. Experiments have been made on the control of tomato leaf mould (Cladosporium fulvum) by fungicides and fumigants. The results showed that most fungicides gave better control of the disease when Agral I was added as a spreader instead of saponin. Effective control was obtained on pot plants sprayed with ammonium copper carbonate, colloidal sulphur A, and salicylanilide. Preliminary trials on commercial nurseries showed that ammonium copper carbonate and colloidal sulphur A were suitable fungicides for use on glasshouse tomato crops. Further work showed that ammonium copper carbonate was useful for spraying diseased tomato crops.2. The disease was controlled by the fumigants ethylene dibromide, quinone, and thymol, in laboratory experiments, and by quinone in trials made in a small glasshouse. Further work is necessary to ascertain if quinone fumigation is practicable for the control of tomato leaf mould in large glasshouses.3. Fumigation with Campbell's sulphur vaporiser protected only the upper side of the leaves from the disease and also failed to kill the spores on the under side of diseased leaves. Experiments made to determine on which leaf surface infection occurs under natural conditions were not successful, but inoculation tests showed that infection may occur on either side of the leaf.4. It has been shown that large empty glasshouses may be practically freed from infection by fumigation with formaldehyde or sulphur dioxide.
ON the Structure of the Immature Stages of the Frit Fly (Oscinella Frit Linn.)
Authors: Steel A. 
Published: February 2008

Summary.1. The morphology of the immature stages of Oscinella frit are described and figured and certain observations of a biological nature are recorded.2. The egg is described together with the method of eclosion of the first instar larva.3. The structure of the larva in its three instars is described in detail with particular reference to the cephalo‐pharyngeal skeleton and the spiracles.4. The first instar larva differs markedly in structure from that in the two instars which follow. Larvae in the second and third instars are distinguishable, apart from size, only in small structural details.5. The puparium is described, with particular reference to the spiracles, together with its method of dehiscence during the exit of the imago.
Leaf‐Spot Of Oats, Helminthosporium Avenae (Bri. And Cav.) Eid.
Authors: TURNER D. M. , MILLARD W. A. 
Published: February 2008

Summary.1. The symptoms of the disease are defined. There are two well‐marked phases as described by Ravn (1) on the seedling, (2) on the mature piant. The fist of these is responsible for considerable loss in seedling oats. The second brings about the infection of the grain. Both spot and “stripe” lesions are produced.2. The disease is especially dependent upon climatic factors. Under adverse conditions the extent and degree of infection is greatly increased, whilst with favourable conditions even plants from infected seed may escape the disease. It is for this reason that the disease assumes serious proportions in northern districts, where an inclement spring is the rule rather than the exception.3. The causative organism of the disease has been isolated and its pathogenicity verified. It is not pathogenic to wheat or barley.4. The disease is seed borne by adherent spores and resting mycelium within the pericarp. The percentage infection by spores on a number of commercial samples of Scottish grown oats ranged from 6 to 62 per cent.; the resting mycelium, however, is the more common and the more dangerous type of infection.5. The infection of the seedling by the fungus has been investigated. The mycelium within the pericarp penetrates the scutellum and the epiblast during the early stages of germination, and this is followed by the invasion of the first, second and third leaves. If the growing point is reached the seedling is killed. Spores are produced abundantly on the dead leaves and initiate the secondary stage on the fifth and subsequent leaves.No parallel has been found between the mode of infection described and that stated to occur in the smuts. The production of a “stripe” is due to the coalescence of individual spots, and there is, therefore, no analogy between the formation of such lesions and those of stripe on barley as described by Smith.6. The morphological and cultural characters of the causative fungus have been described and compared with those of other workers. The conclusion is drawn that it is identical with the H. avenae (Bri. and Cav.) Eid., and that whilst its close relationship to H. teres is admitted there are certain morphological and considerable cultural differences between the two species.7. Control measures for the disease are discussed.
A DISEASE OF THE ARUM LILY CAUSED BY PHYLLOSTICTA RICHARDIAE, N.SP.
Authors: BROOKS F. T. 
Published: February 2008

SUMMARY

A serious disease of the Arum Lily (Richardia africana) is described, which causes the formation of large brown blotches on all parts of the aerial shoot system.
The cause of the disease is Phyllosticta Richardiae n.sp., a diagnosis of which is given.
Suggestions are made for the control of this disease both under glass and in the open.
STUDIES ON BACTERIA ASSOCIATED WITH THE CHOCOLATE‐SPOT DISEASE OF BROAD BEANS1
Authors: RIKER A. J. , RIKER REGINA S. 
Published: February 2008

SUMMARYA bacterium which resembles Ps. seminum Cayley has been isolated from broad beans showing symptoms of chocolate spot in the field. The broad‐bean organism was found to be vigorously pathogenic to broad beans and to garden peas grown in the greenhouse. Two strains have both been passed five successive times through the cycle of isolation, inoculation into broad‐bean plants, the production of disease, and re‐isolation. Further study is necessary before a causal connection between this organism and the disease can be regarded as established.Temperatures between 20 and 30o C. and high humidity favour infection.Histological studies of stems which became diseased following puncture inoculations showed the presence of the broad‐bean organism within the vessels, in the intercellular spaces, and inside the cells of the invaded tissue. The tissues about the vessels and immediately under the epidermis seem to be invaded earlier than other tissues.Bacteriological characters of the broad‐bean organism are described.A non‐pathogenic strain was found which corresponded in bacteriological characters with the pathogenic strains.
THE GROWTH AND RESPIRATION OF BACTERIA IN SAND CULTURES IN THE PRESENCE AND ABSENCE OF PROTOZOA1
Authors: TELEGDY‐KOVATS L. DE 
Published: February 2008

SUMMARYExperiments have been carried out on carbon dioxide production from sand cultures with peptone and glucose solution inoculated with various types of bacteria and protozoa, and with glucose and ammonium sulphate solutions of varying concentrations and C/N ratio. The following results were obtained:

The presence of protozoa increases the carbon dioxide production especially in mixed bacterial cultsres
The increase of carbon dioxide production is greater in glucose solution than in peptone.
A further increase in the number of protozoa has an unfavourable effect on the carbon dioxide production.
The number of bacteria is smaller in the presence of protozoa than in their absence, but the bacterial efficiency is greater and more uniform.
The bacterial numbers and carbon dioxide production are definitely correlated in peptone, but in glucose to a less degree especially in the presence of protozoa.
The reduction of concentrations of glucose from 0–6 to 0–2 per cent. resulted in a greater percentage production of carbon dioxide.
With a lower concentration (0–2 per cent.) of glucose the presence of protozoa causes a greater increase in carbon dioxide production than in higher concentrations (0–6 per cent.).
In the absence of protozoa increasing the C/N ratio had no or only a slight depressing effect on carbon dioxide production.
In the presence of protozoa increasing the C/N ratio is followed by a marked increase in carbon dioxide production.
In bacterial cultures a lessening of the C/N ratio below 10/1 results in a fluctuation of bacterial numbers.I am indebted to Sir John Russell for his kindness in giving me facilities to carry out the work in this Institution. The work was done in Mr D. Ward Cutler's department, and I take this opportunity of expressing my gratitude for his ever ready help and unfailing kindness. For the culture of Colpidium I am greatly indebted to Miss Jane Meiklejohn of the same department.
A BARK DISEASE OF COFFEE IN EAST AFRICA
Authors: STOREY H. H. 
Published: February 2008

SUMMARYA disease of the bark of young leader shoots of arabica coffee occurs in the Usambara Mountains of Tanganyika Territory. The disease may be important when “stumping” is practised in the regeneration of old plantations. A brown sunken lesion, formed of dead extra‐cambial tissues, usually gradually extends and rings the shoots; after a period varying from a few days to several months after complete ringing the foliage above wilts and dies. A leaf spot is also due to the same cause.The fungus, Fusarium lateritium Nees var. longum Wr., among several isolated from lesions, has been shown to be capable of reproducing the disease by pure culture inoculation. A proportion of the experimental inoculations resulted in the ringing and death of the shoots; many of the lesions, however, after a time ceased to advance and became callused at the margin. Similar recoveries from the disease were observed in the field.Field observations and experiments demonstrated that a common mode of entry of the fungus into the stem tissues was through freshly exposed leaf scars, and occasionally from a leaf‐spot down the petiole of a leaf. Many shoots also in the field became diseased as the result of the fungus passing to them through the tissues of a stump from the base of a dead shoot. Coffea arabica alone, of a number of coffee species tested, was susceptible to any extent to this disease.Excision of the affected bark of a stump was effective in checking the spread of the fungus through the stump. The operation, however, is not considered to offer a practicable means of control in the plantation.
AN ECOLOGICAL STUDY OF CLOSELY CUT TURF TREATED WITH AMMONIUM AND FERROUS SULPHATES
Authors: BLACKMAJST G. E. 
Published: February 2008

SUMMARYThe changes in botanical composition of closely cut turf (such as that of lawns) which result from the periodic applications of heavy dressings of ammonium sulphate have been followed at five centres during a period of 3 years. These dressings were applied at the rate of 3 lb./1000 sq. ft. (1–2 cwt. per acre) every 2 weeks during the spring and summer months. The applications were “watered in” to avoid injury from a solution of high concentration.A method of botanical analysis by means of randomly selected quadrats was employed. The changes in botanical composition are expressed as changes in the area covered by each individual species. The data have been treated statistically where possible.As a result of the treatment the areas covered by the weeds (i.e. all species other than the Gramineae) were greatly diminished. Some species such as Trifolium repens and Achillea Millefolium were more susceptible than others. As an illustration of the order of magnitude of this effect it was found at one centre that there was a decrease in “total weeds” (i.e. the sum of the areas covered by individual species) from 17‐0 to 3–7 per cent., between April and September, of the total area examined. On the control plots the changes were slight.A reduction in the “total weeds” was associated with an increase in the area covered by the grasses, the dominant species in each case showing the greatest expansion.In addition to trials with ammonium sulphate, two experiments were carried out, one with ferrous ammonium sulphate and the other with an equivalent mixture of ferrous and ammonium sulphates. It was found that both these treatments produced greater reductions than ammonium sulphate alone. In one case ferrous ammonium sulphate at 10 lb./1000 ft.2 reduced the “weed area” from 12‐5 to 0–3 per cent., while ammonium sulphate applied at an equivalent nitrogen rate, reduced the area from 10‐6 to 5‐0 per cent, during the same period.The changes of soil reaction show that the view that soil acidity is a pre‐requisite for weed diminution by ammonium sulphate is untenable.It is suggested that the effect of the ammonium sulphate is due to a differential action of the ammonium ions, which are toxic to the majority of the weeds while increasing the growth of the grasses.The writer wishes to thank the Secretaries of the Bishop's Stortford, Royal Worlington, Gog and Magog and Stoke Poges Golf Clubs for their help, and also to express his gratitude to Sir Frederick Keeble and Mr Page for their suggestions. Finally, he is indebted to Mr Marmoy of Jealott's Hill for the bulk of the pH determinations.
ON THE GALL MIDGES INJURIOUS TO THE CULTIVATION OF WILLOWS
Authors: BARNES H. F. 
Published: February 2008

SUMMARY

The bionomics of the bat willow gall midge (Rhabdophaga terminalis H.Lw.), which does serious damage to certain willows grown for basket making and the cricket bat willow grown for sets, have been studied.
The midge exhibits a distinct host‐plant preference, choosing the bat willow (S. coerulea) when possible. But it also breeds readily on a golden willow, S. alba var. vitellina. It will not attack Black Maul (S triandra), Long Skin (S. viminalis) and Dicky Meadow (S. purpurea).
It is shown to be a species which sometimes occurs in epidemic numbers. Intensive cultivation is suggested as a control.
EXPERIMENTS IN ENGLAND, WALES AND AUSTRALIA ON THE EFFECT OF LENGTH OF DAY ON VARIOUS CULTIVATED VARIETIES OF WHEAT
Authors: FOESTEE H. C. , TINCKEE M. A. H. , VASEY A. J. , WADHAM S. M. 
Published: February 2008

SUMMARY

This paper reports the results of experiments carried out in Surrey and Cardiganshire (lat. 51o 19′ N. and 52o 25′ N.) and a t Werribee in Victoria (lat. 37o 54′ S.) designed to test some Australian and British wheats grown under various periods of illumination. Light of weak intensity (4–5 c.P.) was employed to prolong the daily period.2. Generally the Australian varieties were “earlier” at all centers under all periods of light than the British.
A sharp distinction between the reaction of spring and winter varieties was observed under short periods of light.
Retardation or omission of floral development was always accompanied by prolonged vegetative vigour. The influence of such treatments upon the longevity of the plants was observed.
Observations are made upon the relationship of the photoperiodic response to the geographic source of varieties.
The results are very briefly considered from the standpoint of the C/N hypothesis and the utilisation of the products of photosynthesis.
Certain economic aspects of the work are indicated.