摘要:

General summary.1This paper describes experiments in the transmission of streak disease between maize, sugar cane,D. horizontalisWilld. andE. indicaGaert. The leafhopper,Cicadulina (Balclutha) mbilaNaude, acted as the transmitting agent and was usually manipulated by the single‐leaf cage method.2The virus of maize streak disease is incapable of causing permanent infections of sugar cane. This conclusion is based on a considerable series of leaf‐cage experiments, in the greenhouse and in the field, and upon a large‐cage experiment. It is confirmed by certain field observations.3The maize virus frequently caused transitory infections of Uba cane, in the form of a few large chlorotic streaks on the leaves. From these streaks the virus was re‐transferred to maize. All evidence indicated that the cane plant made a complete recovery from this transitory infection and ceased to harbour the virus.4The virus from Uba cane readily infected Uba cane. When transferred to maize it produced in this species only a mild form of streak disease, distinguishable with certainty from normal maize streak. Repeated passage of the cane virus through maize failed to enhance its virulence to maize. Infection by the cane virus afforded no protection to a plant from infection by the maize virus; nor were hoppers similarly protected.5Streak disease was discovered in the cane variety P.O.J. 213, hitherto regarded as immune. The virus from these plants produced normal streak in Uba cane and the mild form of streak in maize. After many failures the disease was transmitted experimentally to this variety from Uba cane and from P.O.J. 213 naturally infected in the field. Cuttings taken from diseased plants of P.O.J. 213 frequently produced entirely healthy plants.6Lists are given of cane varieties which have been proved to be susceptible to streak disease and of those provisionally regarded as immune.7A list is given of species of wild grasses believed to contract streak disease in the field.8Streak in D.horizontalishas been transmitted fromD. horizontalsand to and from maize, but not from cane. The virus from a naturally diseasedDigitariaplant, however, showed a virulence to cane greater than the maize virus.9E. indicawas not successfully infected from maize or Uba cane. It was once mildly infected from P.O. J. 213, and was temporarily infected fromEleusine.10In experiments infective leafhoppers survived in the open through the winter at Durban and infected maize in the following spring. The infection of maize in the spring in Natal is thought to be caused usually by survival of the virus in overwintering leafhoppers and not in perennial host

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07240.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07241.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.A bacterial shoot wilt, observed at the East Malling Research Station in 1923 and 1924, is described.A bacterium isolated from infected shoots has been shown by inoculation experiments to be the cause of the disease.The organism not only infects young green shoots, but experiments have shown that it can also cause leaf spots, and that it can induce gummosis and cankers on woody branches and on stems.Cultural studies of the organism suggest that it has not previously been described, so the namePs. prunicolais proposed for it.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07242.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1In the Douglas fir the abscission layers and associated tissues are laid down early in the development of the leaf.2The extent of development of the protective layer has no causal relationship with leaf fall.3Infection withR. Pseudotsugaebrings about a marked decrease in the water content of infected leaves.4The abscission mechanism is efficient at an early stage in the life of the leaf, provided the necessary physiological conditions are present andR. Pseudotsugaeis capable of providing these conditions.The author wishes to express his indebtedness to Dr Malcolm Wilson for his valuable supervision of the work and criticism of the manuscript.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07243.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1Data are given showing that the process of enriching the atmosphere with carbon dioxide affects the tomato plant slightly in many different ways, the sum of these tending to an increased yield of fruit.2These effects include (1) shortening of the period between opening of the flower and picking of the fruit, (2) high percentage of blossom developing into fruit, (3) lower percentage of fruit retarded in ripening,(4) better development of the truss normally most poorly developed,(5) earlier development and ripening of trusses in the later part of the season, (6) better swelling of the fruit at the end of the season.3Conclusions are drawn from the data that the results of an increased concentration of carbon dioxide are most beneficial to the plant at periods of low fruit‐production. These periods are discussed as occurring in the life of the commercially grown tomato plant.4The greatest percentage increases in weight of fruit of the treated plants over the controls are picked from the trusses which develop at such periods in the life of the plant.In conclusion the writer is indebted to Dr W. F. Bewley, Director of the Cheshunt Experimental Station, and Dr F. G. Gregory, of the Imperial College, for valuable suggestions in connection with the tex

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07244.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.Investigations were made of the degree of infestation of plants grown in light soil and in clay soil sown at different dates. The plants sown late in the season in light soil were more affected by the thrips, the infestation being relatively high almost from the germination of the plant and causing death before the flowering stage was reached. On the blocks of plants in light soil sown earlier in the year the infestation was relatively low for a considerable period, and although, at the end of the season, the thrips became very numerous on these plants it was not until after the bolls had been formed, and in this case the practical damage was small.The plants sown in clay soil at different dates did not show such a marked difference in the degree of infestation, and all were less infested by the insects than the corresponding blocks of plants in light soil. This corroborates the findings of previous experiments, namely, that plants grown in light soil are found to be more heavily infested byT. tabacithan plants grown under similar conditions in clay soil.I should like to take this opportunity of thanking Prof. Dunkerly for his helpful criticism, Miss R. M. Smith and Mr I. Thomas for their assistance in making the counts, and Mr R. Stewart for his analysis of the soils used.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07245.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

SUMMARY.A study has been made of the life‐history and habits of the pith moth of the apple.The adults, which are described, emerge during the latter part of July.The eggs, a description of which is included, are laid singly on the twigs, usually near the base of the buds. Incubation requires 14 to 17 days.Immediately on hatching, in the first half of August, the larvae tunnel into the bark of the twigs, without first feeding on the leave

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07246.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Summary.1The paper deals with areas under the Mediterranean type of climate where periods of moisture supply and lower temperature with lowered evaporation alternate annually with periods of low moisture supply and higher temperature with increased evaporation.2The suggestion is made that in such areas where no system of economic production has already been evolved permanent pasture formation for stock production on a system of extensive husbandry would be economic.3That permanent pasture could be produced economically by a plant association capable of regenerating itself annually after the drought stress period owing to the production of a large number of seeds by its individual members.4That the stock carried by such a pasture during its production period could be carried over the alternating drought period of low or nil production by a self‐perpetuating grain crop along the lines adopted in West Australia using the lupin.5Various difficulties and amendments of the system proposed are mentioned and discusse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07247.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY

摘要:

Book reviewed in this article:Manual of Bacterial Plant Pathogens.By CHARLOTTE ELLIOTT.Fungous Diseases of Plants in Agriculture, Horticulture and Forestry.By JACOB ERIKSSON.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1930.tb07248.x

出版商:Blackwell Publishing Ltd    

年代:1930

数据来源: WILEY