摘要:

SUMMARY.The black lines ofArmillaria melleuhave been found in the tissues of a number of plants. Isolations were made from the lines and an account of the development ofArmillaria melleain culture is given. Particular mention is) made of the formation of sclerotium‐1il.e bodies in the culture medium and of the development of the rhizomorphs. Pure cultures of the fungus on wood blocks have produced black lines in the substratum similar to those occurring in nature. A short review is given of the nature of the sclerotium, and from a consideration of the formation of the black plates, or lines, as they appear in section, the suggestion is made that they form the limiting layer of sclerotium‐like bodies, which are partly immersed in the substratum. The black lines in the wood are continued at the surface as the black rind of an effused mycelial mass named the black xylostroma. Thus there is formed a body comparable to a sclerotium in that it is completely surrounded by a black rind of bladder hyphae and has a medulla of hyaline hyphae. It is, however, partly immersed in the wood substratum and, in consequence, contains a considerable proportion of host tissues. Further, this body, probably as a result of its immersion in a hard woody substratum, has developed the power of apical growth resulting in

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06887.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.The evidence for the common opinion that potato plants above a certain age are on that, account more susceptible to blight than younger ones is based on (1) general field observations, (2) dates of planting experiments, (3) artificial inoculation experiments. The results of such observations and experiments are discussed and summarised, and it is shown that they do not consistently support this opinion; further, it is pointed out that much more careful analysis than is usually employed is needed to interpret the results correctly.The difference in behaviour towards blight sometimes observed between assemblages of old and young plants appears in reality to be due to variation in “epidemic potentiality,” and not to change in inherent susceptibility with age. It is not necessary to assume the existence of differences in susceptibility between plants of different ages, for the differences in disease intensity and resultant rate of spread will follow from the increasing chances of the occurrence of primary infection foci as the plants become older, and from the greater chances of the environment (particularly the micro‐climate) being suitable for the development of the parasite amongst older than amongst younger plants. Accurate conclusions concerning inherent resistance or susceptibility are possible only from carefully controlled artificial inoculation experiments carried out under uniform optimum infection conditions. Seedlings are often readily attacked so that youthfulness does not confer any degree of resistance on the plant. The results of experiments hitherto carried out with older plants are conflicting, and further study of the problem on carefully planned lines is eminently desi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06888.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. A comparative study of the rates of respiration, as measured by the weight of carbon dioxide evolved, has been made with healthy and leaf‐roll infected potatoes at all stages in the life cycle, under anaerobic as well as aerobic conditions.2. Except for a short period covering the end of dormancy of the tuber to the first unfolding of the leaves, the infected plant respires at a much lugher rate than does the healthy one. This is true also when the conditions of light, temperature, and external carbon dioxide approximate to those present in the fiel

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06889.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. Analyses of healthy leaves and of leaves infected with mosaic disease (N. tabacum) show that the diseased leaves contain higher proportions of nitrogen and lower proportions of carbohydrate, these differences being apparently increased during photosynthesis.2. In leaves kept in the dark for 68 hours, carbohydrate losses are similar but fall chiefly on insoluble carbohydrate in healthy leaves and on disaccharides in the diseased leaves.3. In diseased leaves, protein breakdown is retarded and insoluble substances are less readily hydrolysed.4. The diseased leaves resemble older leaves in their metabolism.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06890.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.By means of extensive cutting‐up test's on tomato plants inoculated with tobacco mosaic the following points have been determined:1. Confirming the work of Holmes, there is no movement of virus from the inoculated leaf for the first 3 or 4 days. This period is slightly less or considerably more according to the greater or less activity of growth of the plant.2. When the virus passes out from the inoculated leaf it travels first to the roots of the plant with such speed that it can seldom be intercepted at intervening positions.3. Usually about a day later it travels with equal rapidity to the top of the plant.4. In the earliest stages of entering the stem virus particles may be separated by considerable distances (at least several centimetres), since successive samples taken from the stem may yield lengths of 21/2cm. (the length of the cuttings) free from infection. interspersed irregularly between portions containing the infection.5. The presence of developing fruit trusses on the stem may cause part of the virus to travel upwards as far as these trusses at the same time that the initial downward movement is occurring.6. The virus enters developing fruits at the same time as it travels through the stem, whereas adjacent leaves remain uninfected for days or weeks.7. In pot plants, after the initial rapid infection of the developing leaves at the top of the plant. the more mature leaves become successively invaded from the top downwards and from the bottom upwards until the plant is completely invaded by the virus. Complete invasion occurs very quickly in small vigorously growing plants; it may take 3 weeks or more in medium sized plants (Text‐fig. 2); and as much as 2 months in large fruiting plants (Text‐fig. 3).8. Complete invasion never occurs when large field plants of tobacco or tomato bearing a number of mature leaves are inoculated. The mature leaves remain free from virus, apart from a limited movement along the mid‐ribs, for periods of more than 3 months following inoculation (Text

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06891.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1Three types of “breaking” are distinguished—full, “self and “clotted.”2The evidence points to “full break” being the product of two viruses.3“Self breaking” may be selectively transmitted by the aphis vectorsMyzus persicaeSulz andMacrosiphum geiRoch.4“Self break” tulips only transmit “self breaking.”5“Clotting” is an expression of “full break” in certain varieties.6Anuraphis tulipaeB. de Fonsc. is a definite vector in the bulb store but not on the growing plant.7At a certain stage of growth tulips c

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06892.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. The economic importance of the Thysanoptera as an order of insects and the necessity for a revision in the classification of the order are pointed out.2. The past confusion between some common and destructive species of the genusThripsis unravelled and the reasons for this confusion are set out.3. The range of variation, within the species, of characters which have in the past been used for the separation of species in the genusThripsis illustrated, this relating especially to measurements of the antennal joints and of setae upon the body. New structural characters of true specific value, especially relating to the chaetotaxy of the abdomen, are illustrated by examples.4. Variation in colour and the shape of the head are referred to.5. Characters of a constant nature for the species and of value in determination are set out, together with some account of the abdominal structure.6. Quick and reliable methods for the mounting of specimens for microscopic examination are given.7. Specific characters, which enable them to be distinguished from one another, and from other species, are given for some common British species of the genusThrips.8. A general account of the biology and a more detailed account of that relating to some common species is given.9. Lines upon which a sounder classification of the Thysanoptera than at present exists are outlined.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06893.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

摘要:

Summary.1. A severe attack by a flea‐beetle,Psylliodes hyoscyamiLinn. onHyoscyamus nigerL. grown as a commercial crop is recorded.2. The life history and developmental stages of the beetle are described.3. Suggestions for control are made.4. The larvae ofLonchaea flavidipennisZett. (Sapromyzidae, Diptera) has been found associated with the beetle larvae in the damaged stem

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06894.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06895.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1934.tb06896.x

出版商:Blackwell Publishing Ltd    

年代:1934

数据来源: WILEY