摘要:

SUMMARYFrom the results for the onion varieties examined it is demonstrated that high relative rates of water loss and high total water losses are characteristic of non‐keeping types. This is so especially in the period immediately succeeding harvest, and the argument is therefore put forward that actual keeping tests are unnecessary when classifying, for example, new lines as keepers and non‐keep

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05031.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The disease of fine turf known in America as “dollarspot” occurs in all parts of Great Britain but is less prevalent than some other turf diseases.2The causal organism exists as several strains which maintain their respective characteristics under natural and cultural conditions. The strains differ in capacity for spore production; one yields ascospores and conidia, another ascospores only, and others reduced sporiferous structures only.3The U.S.A. strain and an Australian strain, as also some British isolants, belong to the last‐mentioned group.4The organism is characterized by well‐developed aerial mycelium, parts of which become reddish brown or cinnamon in colour; by sclerotial structures of parchment‐like thickness, in size from small flakes to expansive areas, olivaceous to black in colour; and by sporiferous structures arising from sclerotial sources.5The ascigerous fructification is an apothecium which reaches full development with ascospores in spring; the conidiophore becomes cupulate and bears conidia toward autumn.6The rate of growth of the strains and germination of spores is recorded for the rangepH.4–8.7The optimum temperature for growth of British strains is 20–25° C, the minimum 0–1° C, and the maximum 35–37° C. The possible influence of temperature on the establishment of non‐sporing strains abroad is discussed.8The organism is namedSclerotinia homoeocarpa, and a La

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05032.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYChocolate spot disease of broad and field beans in Britain is caused by forms ofBotrytis cinerea.This disease should not be confused with the chocolate‐coloured lesions ofAphisinjury, frost injury, mechanical injury, etc., and leaf spot (Cercospora FabaeandAscochyta Fabae).All forms ofBotrytis cinereatested and some other species ofBotrytiswere capable of causing chocolate spot.B. cinereawill attack other species and genera of the Leguminosae, producing in some instances lesions similar to those of chocolate spot disease of beans.Chocolate spot infection is of two types, “aggressive”, causing blackening and death of part or the whole of the shoot system, and “non‐aggressive”, causing discrete or coalesced chocolate‐coloured lesions. The former type of attack is responsible for the greater part of the damage done by epidemics of the disease.Under suitable environmental conditions, there is a progressive increase in the total number of visible lesions over a period of at least 5 days after treatment with a suspension ofBotrytisspores. When a dilute spore suspension is used “non‐aggressive” infection occurs. When a dense suspension is used, “progressive” infection results in “aggressive” infection: if, however, plants are removed after 24 hours to an environment unsuited to infection, the attack remains “non‐aggressive”While hyphae are abundant in the lesions of “aggressive” infection only a sparse mycelium is present in those of “non‐aggressive” infection.The maximum temperature for infection is about 30° C, the optimum about 20° C. and the minimum between +1 and ‐1° C. A water film is essential for infection, and any factors increasing the rate of evaporation of this film inhibit or decrease infection.The optimum conditions for “aggressive” infection are (a) the presence of large numbers of spores of the pathogen, (b) rain, (c) high humidity and rain to maintain the water film on the foliage for some days, (d) little or no wind and (e) a temperature between 15 and 20° C.Statistical treatment of data has established a correlation between rainfall and the severity of chocolate spot disease. Epidemics are correlated with abnormally heavy rainfall during the critical months of April, May, June and July.Spores ofB. cinereawill remain viable on the leaf surface for periods of more than a month under adverse conditions.Any factor tending to weaken the crop, such as sour soil, potash and phosphate deficiency and waterlogging of the soil, renders it more liable to “aggressive” infection. In addition, chocolate spot disease appears to be favoured by a dense stand of beans and shelter from the prevailing wind.No economic method of control has been found. Care should, however, be taken to see that the crop is

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05033.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1An introductory survey is given of the distribution, synonyms, etc., ofPolyporus betulinus(Bull.) Fries.2In an investigation of the parasitism of the fungus negative results were obtained from infection experiments, but field observations force the writer to the opinion that the organism is a wound parasite.3The effect of the fungus on attacked wood was traced in nature and in culture. The type of breakdown produced is regarded as a red‐brown cubical rot, attacking both sapwood and heartwood.4A study of the enzyme content of the fungus showed that it contained ferments capable of attacking lignin.5The characters of the mvcelium were investigated and the fungus is classified according to Fritz's work.6Black lines are formed in culture. They are frequently related in position to bulbils (sclerotia). It is suggested that here, as elsewhere, the hyphae of the black line may be regarded as forming the limiting layer of a resting stage of the fungus.7The fertile portion of the sporophore consists of a hymenium lining very numerous pores. The basidia form a continuous row of club‐shaped cells, interspersed with cystidia. These latter appear to be the terminal portions of fibre hyphae. The sequence of nuclear phenomena in the basidium was traced. The period of spore discharge was determined for the species and for individual sporophores.8The life of the fungus has been observed from spore to spore in culture during a space of 3 months.9Monospore cultures were obtained. The fungus is heterothallic. The spores were shown to fall into two groups when twelve monospore colonies were paired in every possible way. Monosporous mycelia have single nuclei and no clamp connexions. Mycelia which are polysporous in origin contain conjugate nuclei and bear clamp connexi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05034.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYThe wild grassland speciesPs. campestrisandPs. arvensisshow very different physiological characteristics from the cultivated varieties, and the wild haystack mushroom occupies an intermediate position, showing some of the characteristics of both.The number of spores on the basidium is correlated with these physiological differences.The two wild grassland species will not grow on stable manure compost or on any artificial medium fermented from 14 days onwards.The wild haystack mushroom also fails to grow on stable manure compost, but will tolerate the by‐products of 14 days' high‐temperature fermentation (not longer), and a compost fermented at a low temperature for 1 month.The cultivated varieties will grow on unfermented composts and also on high‐temperature composts up to 35 days, and on prolonged low‐temperature composts, but show varietal differences in the latter.A standard unfermented compost for growing spawn of all forms is described.In conclusion I wish to acknowledge my indebtedness to Dr D. A. Coult for his suggestion as to the effect of lime on the growth of the wild species; to Mr H. C. Osterstock for taking some of the photographs for the plates, and to the laboratory assistant, A. F. Emarton, for some of the photographs, and for his valuable assistance in the preparation of numerous artificial composts, and the manipulation of the large tube and battery jar c

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05035.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Symptomatology, of which a study of “carriers” is regarded as one aspect, tends to be used as a means of segregating “unit” viruses rather than as a means of furthering plant physiological studies. The effects of changes in environmental conditions of growth, acting through the unstable metabolism of a plant upon a virus, have not been adequately studied. Until this is done, the specificity of the reactions said to be due to a unit virus must remain in doubt and, with it, the whole foundation of the biological methods of segregating viruses.2The symptomatological unit is the plant cell, and the clinical picture resulting from infection is the expression of the varying degree to which invaded cells dominate, or are dominated by, a virus. Successive stages in plant dominance are shown by (a) discontinuous or local symptoms; (b) symptomless shoots; (c) individual carrier plants in a variety usually reacting to infection; (d) carrier varieties.3The conditions under which the power to suppress symptoms can be broken down are discussed. Masked symptoms are revealed by relatively slight environmental changes, but the breakdown may be the more difficult to achieve as perfect “carrying” is approached. There is no fundamental difference between “masking” and “carrying”. The conditions under which masking can be converted into carrying are also discussed.4Evidence is submitted to show that a perfect carrier plant is not only unaffected in vigour as a consequence of carrying a virus, but may thereby exhibit a reduced susceptibility to certain other viruses in the field.5Field trials are described in which proof is given that the viruses carried by the varieties King Edward VII (paracrinkle), and Up‐to‐Date (streak and virusX), were not transmitted to intolerant varieties under the most favourable conditions. These carrier varieties are not therefore the serious menace to other varieties they are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05036.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Brief mention is made of the plants attacked byLeptobyrsa rhododendriHorv. and of the problem of immunity and susceptibility of rhododendrons to attack by the bug.2The methods and habits of feeding ofL. rhododendrion rhododendrons are described. The principal feeding method consists in probing the leaf with the stylets and results in the production of a characteristic, whitish mottling on the upper leaf surface (lesion I). A less common feeding method, in which no probing occurs, often produces a brown spot (lesion II).3The character and histology of lesions I and II are described. Lesion I consists mainly of empty palisade cells with an occasional cell showing a similar reaction to saliva as cells in lesion II. Lesion II is composed mostly of unbroken cells which show a browning of the cell contents and the cell walls: apart from the change in colour, the cells in lesion II have, in sections, a normal appearance for at least 3 days after the production of the lesion. No stylet sheath is present in lesion I or lesion II. Toxic action of the saliva appears to play only a small part in the production of extensive damage, most of which results from the emptying of palisade cells (lesion I).4L. rhododendriis a mesophyll feeder and the object of the stylets is the palisade tissue of the leaf. Vascular bundles are only accidentally pierced and never become plugged as the result of salivary action.5Microchemical tests on the brown substance in lesion II are described.6Lesions very similar to lesion II can be made by scratching the surface of a rhododendron leaf with a needle. The production and spread of the brown area around a scratch is much slower than from the puncture made by a bug. The brown material in lesion II is probably produced by the oxidation of chromogens.7The lesions produced byL. rhododendriare discussed and compared with hemipterous lesions described by other workers.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05037.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Full‐grown larvae of Tip&paludosa Meigen were obtained by application to the soil of an emulsion of orthodichlorobenzene, and it is suggested that the larvae become non‐susceptible to this treatment about 6 weeks before pupation. The larvae were reared in pota of soil containing germinating and growing wheat.2The adult crane‐flies were kept in glass tubes for longevity trials which showed that on the average the males lived about 7 and the females 4–5 days. Mating and oviposition took place in these tubes.3Twenty‐seven females laid 5408 eggs, averaging 200 each. About 45 per cent of the eggs were laid the day the female emerged and 40 per cent the fist day after. It is believed that these figures are too low as the regular observations stopped a t 7 p.m. G.S.T. and it is suggested that 75 per cent of the eggs are in reality laid by midnight on the actual day of emergence and 10 per cent on the first day after. The eggs were kept damp in solid watch‐glasses which xere stood in water in culture dishes.4It is shown that by the time the peak of crane‐flies on the wing has been reached, the peak of eggs in the soil will already have been passed.5Hatching took place 11–15 days after the emergence of the parent crane‐fly, 2498 hatching from 5408 eggs. The young larvae were kept in Petri dishes and fed on wheat rootlets, clover or chickweed leaves, pieces of cabbage leaves, slices of potato or bran. By the time the 3rd instar was reached about 54 per cent mortality had occurred, chiefly owing to larvae escaping and cannibalism (576 survived out of 1257). This stage was reached in roughly 14 days.6The breeding potential was as follows: 51 per cent of the nearly full‐grown larvae emerged as adults (this figure is low because of the number of larvae escaping); 75 per cent of the available eggs were laid by the females; 46 per cent of the eggs laid hatched, and 46 per cent of the larvae survived the fist two instars. In other words, under the conditions of the experiment, on the average, one female crane‐fly laid 200 eggs, 92 larvae hatched and 44 survived

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05038.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYAddled brood is produced by defective queen bees and is not of a contagious nature as are the other common brood diseases.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05039.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYVegetative cells ofBacillus larvaehave not produced American foul brood in healthy nuclei even when B dose almost 3000 times greater than an inoculum of spores of this organism capable of causing the disease has been sprayed over the developing brood.A very much smaller inoculum of the spores of B.larvaeis effective in producing American foul brood when the developing larvae of healthy nuclei are sprayed directly with them than when they are fed in syrup to the bees.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05040.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY