摘要:

SUMMARY.1An area was chosen which was as typical as possible of the permanent pasture fields of the district, and in which invasion by insects not belonging to the area would be reduced to a minimum.2In order to define the characters of the area under consideration as clearly as possible, chemical, mechanical and botanical analyses were carried out.3Insects, largely in immature forms, were obtained by examining samples of soil from various parts of the area, and in addition many adults were obtained by sweeping the herbage with a net. The latter method produced also some invading forms which did not belong to the area.4The factors influencing the distribution by depth of the insects in the soil were in this case chiefly occurrence of food, aëration, and moisture, and the result of these influences was that the insects seldom penetrated even as deep as six inches, the vast majority of specimens being found at a depth not greater than two inches.5The census of insects actually found in the samples of soil gave an insect population of 3,586,088 per acre. The family best represented in number of individuals was the Bibionidae, species of which made up 32–4 per cent, of the total number of soil insects. The next in number were the Mycetophilidae 16–7 per cent., and the Staphylinidae 12–2 per cent. With regard to number of species occurring in the soil, the Coleoptera, with 29 species, was the best represented

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05303.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05304.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.This article records the occurrence, in the spring of 1920, of the conidial form ofSclerotinia MespiliSchell. on the leaves of medlar trees in four localities in Kent and one in Somersetshire.Mycelium obtained from dead flowers which had remained on the tree from the previous year gave rise to cultures similar to those obtained from conidia taken from infected leaves but theSclerotiniastage of the fungus was not observed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05305.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05306.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.This paper presents the results so far obtained in an investigation, which has been carried on since 1915, into “spotting” in apples. The symptoms of “spotting” as they are found and develop in numerous varieties of apple are described. Several fungi have been isolated from spots and cultured in various artificial media with the production of spores.They include a new genus of Phomatales (Polyopeus) and nine new species, of which at least one,Pleospora pomorum, as the result of experimental inoculations, has been proved capable of parasitising apples. The fungi do not include any of the species hitherto reported as causal organisms in the United States, the only centre where investigations into the “spotting” of apples, as distinct from the “bitter pit” problem, has been undertaken.The work was commenced at the Wisley Gardens of the Royal Horticultural Society. During the building of the Society's laboratory it was continued, by the kindness of Professor V. H. Blackman, in the Department of Plant Physiology and Pathology at the Imperial College of Science and Technology. In was later carried on again at Wisley; the work however has been completed at the Imperial College.The authors' thanks are due to Professor Blackman for his kind help and criticism during th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05307.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.In this chapter we have continued our analysis of the results of the experiments on the growth of maize carried out by Kreusler and his co‐workers. The rate of growth has been expressed per unit leaf‐area instead of per unit dry‐weight as in the last chapter. The term “Unit Leaf Rate” is used for the weekly rate of increase of dry‐weight in mgs. per sq. cm. The Unit Leaf Rate, instead of undergoing a perfectly definite type of variation, as does the Relative Growth Rate, fluctuates about a mean value. The larger fluctuations which occur in the values for Unit Leaf Rate calculated for the later phases of the life‐cycle have been attributed mainly to sampling errors.Correlations between Unit Leaf Rate and various environmental factors have been determined.The general evidence is that the Unit Leaf Rate is correlated more closely with temperature than with any of the other environmental factors.By allowing for respiration on the basis of our own experimental results values for the real assimilation were arrived at. These also show a closer correlation with temperature than with light.The values for assimilation determined from the Unit Leaf Rate are of a lower order than those determined by the “half‐leaf” method, but much higher than those determined by the “gasometric” method.Finally, the authors wish to express their indebtedness to Dr F. F. Blackmail for his stimulating criticism and help in this and

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05308.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

摘要:

SUMMARY.1The character of the double cross‐grain of the different Indian woods examined is remarkably uniform and conforms to the following generalisations:a The grain alternates between right‐handed and left‐handed in inclination during the growth of the tree, these changes in the inclination being in general synchronous in the trunk at least over lengths of two feet,b That the grain does not consist of alternate right‐and lefthanded spirals is due to the rate of change in inclination of the grain not being uniform at any moment during the growth of the tree either in a tangential or longitudinal direction with the result that the double spiral character is obscured, giving place to a serpentine configuration.2Transitional types of grain between straight grain and the full development of double cross‐grain are due to variations in the—a regularity shown in the length of the successive periods,b regularity in the amplitude of the successive periods,c stability of the periods over longer or shorter tangential and longitudinal distances.3No correlation could be inferred, from the data available, as existing between seasonal changes or periods of growth and the periodicity shown in the inclination of the grain.There were indications, however, that both period length and amplitude increased with age up to a maximum, and that a long period length was correlated with a big amplitude. Period length responds to the general rate of growth for, in trees of excentric growth, the period length was shortest along the smallest radius.4Fibre measurements inCalophyllumsp. andChloroxylon Swieteniasuggest that a longer fibre length is correlated with inclined grain and a shorter fibre length with straight grain.5The character and widespread occurrence of double cross‐grain indicate that it is the expression of some periodic phenomenon whether of internal or external nature, but it remains to be seen to what extent a more extended investigation will bring it into line with other periodic phenomena shown by living organisms.This research was carried out in the Woods and Fibres Department of the Imperial College of Science and Technology, South Kensington, while the author was in receipt of a studentship from the Department of Scientitic and Industrial Research.In conclusion I wish to record my thanks to Professor Percy Groom for suggesting this investigation, providing the material and for help throughout t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05309.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05310.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05311.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1920.tb05312.x

出版商:Blackwell Publishing Ltd    

年代:1920

数据来源: WILEY