摘要:

SUMMARYAn internal soft rot of potato tubers caused byB. carotovorusis described. Various strains ofB. phytophthorus, B. solanisaprusandB. carotovorusare compared with respect to their cultural, pathological and serological behaviour, and the differences seem sufficient to warrant their continued separation into distinct species.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04248.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04249.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

摘要:

SUMMARYA staining method for testing the viability of the winter sporangia ofSynchytrium endobioticumis described. The sporangial contents are pressed out into acid fuchsin or after treatment by a strongly alkaline reagent into methylene blue. The staining reactions have been correlated with the results of infection experiments in pots. Sporangia which, like the controls stain faintly, produce a high percentage infection and are therefore alive. Those which stain deeply and rapidly produce no infection and are presumably dead. There is an intermediate group in which some sporangia stain deeply and some are intermediate in reaction. This group tends to give less infection than the controls.A method whereby sporangia which have been treated in soil may be extracted without affecting their viability is described. The method depends on the difference in specific gravity of sporangia which has been determined as about 1.17 and of soil which is in the region of 2.5. The sporangia are extracted by means of chloroform (sp. gr. 1.5 approx.), which does not affect their viability.A study of the relation of temperature, time and viability shows that treatment for 5 minutes at 90°C., 15 minutes at 80°C., 1 hour at 70°C. and 8 hours at 60°C. have a similar effect in killing all the sporan

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04250.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

摘要:

SUMMARY1A number of experiments were carried out on the exchange of moisture between discs of 1/8th inch and 1/16th inch Birch veneer below the fibre saturation point.2It appears from these experiments that the rate of moisture movement in wood below the fibre saturation point is dependent, not only upon the moisture gradient, but also upon the moisture content. But for this limitation, fair agreement was obtained with the law of diffusion. The values obtained for the coefficient of conductivity have no definite significance as they represent mean values over a period.3The rate of moisture exchange between the discs was found to be approximately proportional to the square of their combined thickness and was within 15 per cent, of the demands of the law of diffusion for these particular experiments.4From the few experiments carried out at a higher temperature it would appear probable that the change in the rate of moisture movement with rise in temperature is proportional to the change in the vapour pressure of water.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04251.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

摘要:

SUMMARY1The paper deals with the members of the genusAgrostisoccurring in the international seed trade; current names are enumerated and, as far as possible, related to each other.2The following relationships are established:

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04252.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

摘要:

SUMMARY1The froghopper (Monecphora saccharinaDist.) is a serious pest of sugar‐cane in Trinidad.2Of the two important aspects of the problem namely (1) the factors controlling the numbers of the froghoppers themselves, and (2) the conditions influencing resistance of the canes to, and recovery from attack, the second is considered in the present paper.3The bionomics of the froghopper are briefly dealt with.4The saliva of the froghopper is slightly acid (pH. 6.0–6.2) and it contains amylytic and oxidising enzymes.5The effect of the froghopper sucking the cane leaf is described, noting especially the peculiar and primary effects upon the border parenchyma.6Later spread of injury is described in detail and various influences at work are considered.7The water relations of the plant appear to be highly important in connection with recovery from injury and retardation of the spread of injurious effects.8Fertilisers have not been shown to aid recovery.9The problem is discussed in several of its aspects and the contents of the paper, with suggestions for further investigation, summarised on pp. 102–106. “Canes do not necessarily show serious blight when froghoppers have been abundant, nor is abundance of the insect a necessary condition for serious blight.” Agreatabundance of froghoppers, of course, is bound to have a seriously deleterious effect, quite apart from the condition of the cane. The importance of water relations is e

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04253.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

摘要:

SUMMARYI. The insects studied are selected as being representative of the group HEMIPTERA. They are: Capsidae:Calocoris bipunctatusFab.,Lygus pabulinusLinn. Typhlocybidae, “Leaf‐hoppers”:Eupteryx auratusLiv.,Zygina pallidifronsEdw. Aleyrodidae, “White Flies”:Asterochiton vaporariorumWestw. Aphididae:Myzus persicaeSulzer,Macrosiphum solanifoliiAshm.,Myzus drcumftexusBuckt. Coccidae:Aspidiotus hederaeVallot.,Dactylopius longispinusTarg.‐Tozz.II. The insects exceptAspidiotus hederae, are studied chiefly in relation to the potato plant.III. (a) Capsidae. These bugs penetrate the tissue by pressure, the passage of the stylets being assisted by the disintegrating effects of the accompanying saliva. The objective of the beak lies in both cortex and vascular bundles. Both leaf surfaces and stem tissue are punctured. The path through the tissue is intra‐cellular. The effect of the saliva upon the cells of the plant host is described in detail.(b) Typhlocybidae. The leaf‐hoppers penetrate the plant by pressure. Both leaf surfaces are attacked, the larvae being usually confined to the lower surface. The stem is not punctured as a rule. The objectives of the stylets are the palisade cells and the vascular bundles. The track of the piercing organ is intra‐cellular. The effect of the saliva is described, the chlorophyll and cell contents are destroyed over a wide area while the cell walls are left intact. There are some indications of a stylet track.(c) Aleyrodes (White Fly) penetrates inter‐cellularly, entrance being made between two epidermal cells, in the case of young larvae often through a leaf stoma. The under surface is always the one attacked. The objective is usually the phloem elements of the vascular bundles, in young larvae the stylets are often confined to the cortex. Damage to the cells of the host was not very evident microscopically, though a few cells showed plasmolysed contents. Very slight indications of a stylet track were visible.(d) Aphides. These insects usually penetrate between two epidermal cells, the track on the whole being inter‐cellular.M. solanifoliihowever, a large aphis, often has an intra‐cellular stylet track. In each case the phloem was the objective. A well‐defined stylet track is formed, most evident in the case ofM. persicae. Damage by the saliva is largely confined to the actual track of the stylets. Some wound reaction is noted in the phloem caused byM. persicae. The under surface of the leaf is usually selected for penetration, the stem is also attacked.(e) Coccidae. Of this groupAspidiotusexhibits an intra‐cellular path through the parenchyma of the host, in this case a Cordyline. The stylets enter the tissue through an epidermal cell. The phloem is not the objective. There is a well‐marked stylet track. Cells in the path of penetration have their contents destroyed. The saliva appears to have the property of dissolving the cell walls.Dactylopius, a mealy bug, also penetrates intra‐cellularly; in this case the phloem and xylem elements are always the objective. On the leaf the insects are situated near or alongside a vein. There is a well‐marked stylet track, the saliva being secreted in large irregular drops. Both leaf and stem tissue are attacked. Some disorganisation of the vascular bundles results from the feeding of this insect. That the saliva ofDactylopiusalso dissolves the cell walls is shown by the ease with which it can penetrate large xylem vessels.A number of photomicrographs illustrating these points are given.IV. A discussion is appended of the relation of the facts elucidated in the study to the question of the transmission of virus disea

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04254.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04255.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04256.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1926.tb04257.x

出版商:Blackwell Publishing Ltd    

年代:1926

数据来源: WILEY