ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06952.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

SummaryA 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.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06953.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

Summary1This paper is an investigation into the mycological flora characteristic of grasslands with particular reference to certain soil types.2Twenty stations were examined over a period of two years, the stations being representative of chalk, clay and sand soils.3The experimental method is briefly described and ecological notes on the twenty stations are given in detail.4Lists of the fungi found on grasslands in general and on each of the three soil types are given, and the constancy of species and frequency of individuals are discussed in relation to grasslands as a whole and in relation to each soil type.5The results are discussed and a comparison made between the fungi of grasslands and those of oakwoods and beechwoods.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06954.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

SummaryAttempts to produce infection of wheat seedlings by the ascospores ofOphiobolus graminisin a variety of natural soils and in sand have failed. Yet, the ascospores germinate well on nutrient agars, and the resulting agar cultures produce infection as readily as cultures obtained from mycelium.Ascospore infection of sterile wheat seedlings growing in sterilized soil may be obtained without difficulty. The nutrients present in sterilized soil are unnecessary for the initiation of ascospore infection, which occurs as freely as in sterile sand. Ascospore infection is, therefore, considered to be inhibited in unsterilized soils and sand by the antagonism or competition of other soil micro‐organisms.In unsterilized sand this antagonism is not sufficient to hinder infection by agar inoculum, nor does it appreciably impede the progress of infection along the roots. It is suggested, therefore, that microbiological interference with the initiation of ascospore infection is a competitive rather than an antagonistic effect, and is due to assimilation by the general soil microflora of the nutritive substances excreted from the growing and developing roots. Only under sterile conditions is this organic detritus available to the germinating ascospores.The results of these experiments render it unlikely that the ascospores can play any part in the survival and dispersal of the fungus under field condition

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06955.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

Summary1Methods of establishing pure cultures of rusts are discussed and a new spore‐proof and insect‐proof cellophane cylinder is described.2Eighty‐two cultures, isolated from collections ofP. anomalain 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.3A mutant, differing in colour (orange and yellow) and in pathogenicity, is recorded forP. anomala.The mutant arose from an unstable culture of race 14 cultivated onHordeum vulgare pallidum(Sudan), and is numbered physiologic race 23.4Segregation and hybridization of physiologic races occurred through the aecidial stage onOrnithogalum umbellatumL. 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.5Several biotypes of physiologic races 12 and 13 were found; they seem to establish a linkage between the two races.6A new selection of differential hosts for the differentiation of physiologic races ofP. anomalaon cultivated barleys is proposed. A “Numerical Table” of the thirty physiologic races and an “Analytical Key” for their determination are given.7The distribution of physiologic races ofP. anomalaon cultivated barleys in Great Britain, Portugal and Spain is discussed.8From field observations it is concluded that at CambridgeP. anomalamay overwinter in its uredospore stage. Evidence is given that in Portugal the uredospores survive the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06956.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

Summary1When a 36‐year‐old tree ofSequoia giganteawas felled it was found to have rotted areas in the wood at the base of the trunk.2One organism only was isolated from wood in these rotted areas.3The general and detailed microscopic characters exhibited by this fungus in culture identify it asConiophora puteana.4In the present case it seems clear that the fungus was acting as a primary paras

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06957.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

SummaryExposure of the Peruvian potato varieties to full summer‐day conditions at Cambridge resulted in a more uniform growing period, and increased the tendency to bloom. The effect on tuber production varied according to the variety. In most types the weight and number of tubers were not adversely influenced, but there was a tendency to elimination of the dormancy period and to conversion of the stolons into aerial shoots. In a few varieties there was no adverse influence, and in the members of one small group plants exposed to full‐day conditions formed no tubers.Investigation of virus content showed that of fifty‐nine varieties only eleven were healthy. In the remaining forty‐eight varieties there were found viruses apparently identical with those known in this country asX, B, C, F, Gand perhaps leaf roll.1There was also evidence of the presence of other viruses, suggesting the existence in South America of a virus complex, only isolated members of which have hitherto been known in Europe. It follows that great caution should be exercised in introducing South American varieties into potato‐growing

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06958.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

SummaryThe contents of healthy cells and those infected with a number of different, plant viruses are described. Some of these viruses apparently do not cause the production of intracellular inclusions; others cause the production of amorphous bodies only, and the remainder produce both amorphous and crystalline inclusions. The properties of the inclusions are compared with those of purified preparations of the viruses. It is shown that insoluble complexes of the viruses with protamines, histones and proteins which in many ways resemble the intracellular inclusions can be producedin vitro.Possible explanations for the formation and disappearance of the inclusions in infected plants are suggested.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06959.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

摘要:

Summary1This 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 1936.2Forty‐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.3The 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.4The results have been summarized in a discussion in which are indicated the special precautions necessary to ensure health in seed‐pota

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06960.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1939.tb06961.x

出版商:Blackwell Publishing Ltd    

年代:1939

数据来源: WILEY