摘要:

Summary.The anatomical modifications in the tissues of plants caused by the action of gall‐inducing fungi and insects are illustrated by a number of examples, and compared with those produced by various processes of regeneration and wound healing or by factors that lead to anatomical changes without the intervention of wounds, such as nutrition, humidity, and the like. It is concluded that all living cells have the potentiality to react to various stimuli by hypertrophy, hyperplasy, or the development of meristeroatic tissues, and that the pre‐existing meristems are not, of necessity, primarily implicated in gall format

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07207.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.A description is given of the intracellular inclusions found inS. nodi‐florumafter inoculation with the virus of the yellow (aucuba) mosaic of tomato. In this plant these inclusions are unusually conspicuous and can be observed in the living cell with exceptional ease. They are of two main types, crystalline spikes and amoeboid bodies, the latter corresponding to the X‐bodies found in other plants. A detailed account is given of their appearance, structure, position in the cells, relation to the nucleus etc. The X‐bodies may be either coarsely granular, looking like aggregates of particles, or more homogeneous; and they have a pronounced tendency to crystallise into the forms commonly seen in protein crystals. They are vacuolate, and occur in all the tissues of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07208.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1Experiments are described on the transmission by different methods of two potato viruses, crinkle on Myatt's Ashleaf potato, and interveinal mosaic on President potato.2The virus of potato crinkle was transmitted by needle scratch to President, Arran Victory and Great Scot potatoes. President developed a mosaic mottling, Arran Victory a crinkle similar to that shown by the source of infection, while Great Scot developed crinkle, together with numbers of streak lesions on the leaves. Negative results were obtained with Big Ben and Up‐to‐Date.3Attempted transmission of the crinkle virus by means of the aphisM. persicaeto potato varieties, President, Arran Victory, Great Scot and Kerr's Pink, was successful only with President, which developed a crinkle of a mild type.4Crinkle scions were grafted on to healthy President, Arran Victory, Great Scot and Kerr's Pink. The first two developed crinkle in a form comparable to the source of infection; Great Scot developed a severe streak which attacked the growing points; there was little or no crinkling; Kerr's Pink showed streak lesions accompanied by mottling.5Needle inoculation of tobacco with the crinkle virus produced a severe necrotic disease, which increased in virulence by progressive needle inoculation through tobacco. When this virus was returned to healthy potatoes of nine different varieties, including Up‐to‐Date which is capable of “carrying” streak, all nine varieties developed a severe crinkle and leaf‐drop streak. Big Ben was the most‘ susceptible and was killed in very case.6Aphis (M. persicae) inoculation of tobacco with the same crinkle virus produced different symptoms from those of the needle; these consisted of spots and faint green lines. When this virus was returned to healthy potato by aphis or needle, crinkle and leaf‐drop streak resulted.7Needle inoculation ofDatura stramoniumwith the crinkle virus produced a well‐marked mottling of light and darker green; when this disease was returned by needle to President potato, a mosaic mottling only resulted.8The virus of interveinal mosaic on President potato was transmitted byM. persicaeto healthy President; negative results were obtained with Arran Victory.9The virus of interveinal mosaic was found to be transmissible by the needle to healthy President.10Interveinal mosaic was transmitted by grafting to President, Arran Victory and Great Scot. President showed interveinal mosaic only. Arran Victory showed interveinal mosaic together with numerous streak lesions, while Great Scot developed a form of leaf‐drop streak.11The virus of interveinal mosaic, when transmitted to tobacco by the needle, produced a well‐marked ringspot. When this was returned to potato by needle, interveinal mosaic developed, with the addition of streak lesions and marked curling and distortion of the leaves. Progressive inoculation through tobacco of the ringspot induced by interveinal mosaic gave an increased virulence. When this virulent virus was returned to healthy potato by needle, a severe form of streak resulted, which obscured the symptom

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07209.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1A description is given of a new virus disease of the top characterised by weakness of growth and by the presence of yellowish (chlorotic) markings on the leaves, accompanied by distortion of the lamina. The name “chlorotic disease” is proposed.2Two instances are recorded where the disease has been transmitted artificially, in one to a healthy plant by budding with a diseased bud, and in the other to a healthy scion by grafting it on to a diseased st

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07210.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.A comparison of streak disease of tomatoes, derived from commercial glasshouses, and experimental streak produced by combined inoculation of the viruses of potato mosaic and tobacco mosaic, is given in detail.The characters employed in comparison are the host range of each virus and its resistance to various temperatures, to different concentrations of alcohol, and to ageingin vitro.Glasshouse streak and tobacco mosaic show an equal resistance to alcohol, heat and ageingin vitro, and have, in addition, an identical host range. Treatment for 1 hour with 90 per cent, alcohol and for 10 minutes at 850C. did not destroy the infectivity of either of these viruses.Glasshouse streak is shown not to contain the virus of potato mosaic, but is of itself able to produce necrosis in tomatoes without the participation of potato mosaic. The factors underlying this have not been determined.It is concluded that tobacco mosaic and the mosaic of glasshouse streak are probably identical, and that much of the streak occurring in glasshouses is due to a single virus, and not a mixed infection of this with potato mosaic.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07211.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1Evidence is submitted to show that mosaic disease of both the cucumber and the tomato is transmitted by the seed.2Stocks of infected seeds have been cleaned by early and careful roguing of diseased plants.3There is every reason to believe that in this country the incidence of this disease in glasshouses can be reduced to small proportions, if not entirely prevented, by the use of clean seed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07212.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1The period between the opening of a tomato flower and the picking of the fruit which develops from it has been termed the maturation period.2Usually, the maturation periods of the different fruits produced by a tomato plant vary considerably.3The maturation period lengthens as the plant ages, and as the truss lengthens.4The graph of the maturation periods of the fruits produced by a tomato plant approaches a straight line as the efficiency of the plant increases.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07213.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1The H‐ion concentration of plant sap most favourable to the growth ofB. tumefacienshas been shown in a previous paper to be aboutpH. 5‐2. This H‐ion concentration characterises meristematic tissue where tumours due toB. tumefaciensoriginate.2The bacterial zoogloea present within and on the surface of the tumours gives the red colour with methyl red which indicates approximately the same value,pH. 5‐2.3The cell wall in contact with the bacterial zoogloea appears to be suberised; and it is suggested that the process of tumour formation is due to healing reactions similar to those which take place in wounded plant

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07214.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.In this investigation of the fungi of the soil of the Dovey Salt Marshes (Ynyslas) 48 fungi were isolated.Twelve of the species found do not appear to have been recorded before for the British Isles.The area investigated is a badly aerated, stiff, tenacious clay, alkaline in reaction (pH 8), with a high water content, due mainly to periodical inundations by tidal salt water.Method of investigation consisted in taking samples of soil from a depth of 11/2 and 31/2 inches and either planting portions of this directly on to specially prepared media, or first shaking up a portion in water and then inoculating the prepared media with some of the suspension.Three fungi–Torula allii, Penicillium hyphomycetisandFusarium oxysporiumvar.resupinatum—were almost invariably present in every sample of soil: almost equally common wereTrichoderma lignorum, T. Köningi, Hormodendron cladosporoides, Mucor circinelloidesandPericonia felina.Most of the fungi found are species found above ground as saprophytes, and may have been introduced into the soil by drainage, etc.The writer considers fungi are active only in association with organic material.The vegetation covering this marsh shows marked zonation: soil samples were chiefly taken from the Glycerietum and Aimerietum.The same species of fungi were common to the two associations.Glyceria maritimais a most effective silt binder, because the stele of its rhizomes and roots consists almost entirely of lignified tissue which does not yield to the activities of the soil fungi; Armeria maritima is not so effective a silt binder because the stele of its rhizomes and roots contains very little lignified tissue—at a depth of a foot, the tap roots of Armeria are little more than hollow tubes, the interiors having been removed by fungi and ba

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07215.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1In view of the rapid development of practical experiments in biological control, a general survey of the subject seems desirable. The foregoing paper designed to meet tins need contains a discussion of the nature of biological control, the character and practical value of biotic controlling factors of various types, the pests to which the method can be applied, the situations in which it can be utilised and the results that may be expected from it.2Bycontrolwe mean a check on the increase of an organism brought about by any cause whatever. Bybiological controlwe mean the reduction of the rate of multiplication of an organism effected through the agency of other, organisms as distinct from non‐living factors.3There is no necessary connection between control as a biological phenomenon and control in the economic sense.4The complex of factors responsible for the control of an organism differs in composition both qualitatively and quantitatively in the various districts inhabited by it; the measures necessary to re‐establish control, in the case of an outbreak, will also vary in different times and places. It would, therefore, be unwise to rely exclusively upon the methods of biological control for the solution of entomological problems.5The main factors of the biological control of insect pests are: (1) Pathogenic organisms; (2) Invertebrate parasites and predators; (3) Vertebrate predators.6Pathogenic organisms are sometimes very effective but practically impossible to manipulate successfully. Among the parasitic and predaceous Invertebrates, the entomophagous insects are by far the most important and the most useful. Vertebrate predators apparently play only a minor part in the control of insect pests, and there is little indication that they can be utilised in practice.7The control of insect pests by the use of entomophagous insects seems, on the whole, much easier to bring about than the control of plant pests by phytophagous insects, in the first place because the insect is much more susceptible to injury than the plant, and in the second place because the entomophagous insect, being of about the same size as its host, is capable of inflicting greater injury than the phytophagous insect can inflict upon the host.8The attempt to control plant pests by phytophagous insects is more dangerous than the attempt to control insect pests by entomophagous insects, because if the phytophagous insect changes its host after introduction it may attack a useful plant, whereas the entomophagous insect, even if it does attack hosts other than that against which it was introduced, is not likely to attack any beneficial insect.9The object of work in biological control may be either:(i) the intensification in the action of natural enemies already present in the area; or(ii) the introduction of natural enemies (a) temporarily absent from the area; or (b) never before present in it.In the latter case the species introduced may be either (i) species of which a known host already exists in the area; or (ii) species of which no known host exists in the area.In general, the most promising type of work concerns introduced 3pecies from other areas, though valuable or, at least, promising results have been obtained in the work with certain established speciec.10The results which may be expected from experiments in biological control depend primarily (other things being equal) on whether the host is increasing in numbers or not. If it is increasing, the increase of the parasite at its expense will not cause a reduction in damage or a decrease in numbers, which will not occur until the parasite has overtaken the host. If the host population has become stabilised, then the increase of the beneficial species at its expense will give immediate relief, though this may be slight at first. The reduction of damage will continue until the rarefaction of the host population begins to cause a diminution in the effective reproductive rate of the parasite, after which the host population will again increase for a time.11Generally speaking, no one species of parasite or predator is likely to bring the host under control over the whole of the infested area. To produce this result, the introduction of additional species will usually be necessary, while in many cases, their efforts must be aided by the methods of agricultural, chemical or mechanical cont

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07216.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY