摘要:

SUMMARY1The emergence of pea seedlings is much, reduced under conditions of high soil moisture. Soil temperature is a factor of less importance. Under comparable conditions, the wrinkle‐seeded variety Gradus is more liable to fail in emergence than the round‐seeded variety Pilot.2By dressing the dry seed with an organic mercurial compound, the stand of plants can be materially improved. The maximum load of fungicide which the dry seed is able to carry gives no visible check to the growth of the above‐ground part of the plant but an appreciable stunting of the tap root of the seedling has been demonstrated.3Reduction in the stand of seedlings is chiefly due to the action of soil‐borne organisms. A species ofFusariumand a phycomycetous fungus, isolated from diseased seedlings, have been shown to be capable of causing a high mortality of pea seeds and seedlings under conditions of high soil h

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05048.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05049.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Resin‐containing cells can be distinguished microscopically in sections ofDenisroots. Only these cells respond to Durham's test.2Rotenone first occurs in small groups of cells in the secondary cortex opposite the protoxylem, when the plant is about 6 weeks old. Thereafter it gradually spreads in scattered groups throughout the xylem parenchyma and cortex.3Starch and rotenone do not occur in the same cell; they occur in mutually exclusive groups.4It is probable that, in a mature root, all the xylem parenchyma contains either starch or rotenone.5The toxic substances other than rotenone probably occur in the same cells as rotenone.6The rotenone‐containing cells are apparently morphologically unspeciali

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05050.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The paper is an investigation into the ecological distribution of the larger fungi with the object of determining the relationship between fungi and vegetation with particular reference to oak woods and beech woods.2Previous literature is briefly summarized.3The experimental method is described.4Results of observations over a period of 5 years on five different vegetation communities are presented from the respective standpoints of(a)constancy of species, and (6) frequency of individuals.5The fungus floras associated with oak woods and beech woods have been dealt with in greater detail and lists of characteristic species have been given for each of the two communities.6An attempt has been made to show the relation between fungal species and ecological types of oak woods and beech woods.7The results have been briefly discussed and suggestions for future work have been put forward.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05051.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

Summary1Culture studies were made with varietiesB1candB12cofBotrytis cinereain which nitrogen was supplied in different combinations. From these studies it became evident that no definite conclusion may be drawn as to whether any of these two varieties prefer nitrogen in the ammonium or in the nitrate form.2Though the growth of these fungi was usually somewhat poorer on the media in which nitrogen was available in the nitrate form, the greatest weight of mycelium was produced per unit weight of consumed nitrogen from this source.3The amount of acid produced per unit weight of consumed nitrogen was greater on media containing ammonium or nitrates which were less favourable to growth.4The hydrogen‐ion concentration of the medium, originally standardized atpH. 6.0, and the total amount of acid of this medium was increased by both varieties ofB. cinerea.The increase in hydrogen‐ion concentration was greater where nitrogen was supplied in the ammonium form than where it was supplied in the nitrate form.5Both varieties acidified all sets of media containing ammonium nitrate as a source of nitrogen, whether the initial hydrogen‐ion concentration waspH 8.6 or 2.7. The sets of media, in which nitrogen was supplied in the form of sodium nitrate, were acidified when their initial hydrogen‐ion concentration waspH. 7.4. Where this concentration waspH 2.6, it was however decreased topH 5.2 by cultureB1c, while the total amount of acid in these sets of media was still increased. CultureB12cnot only decreased the hydrogen‐ion concentration of this medium, originally atpH 2.6, but also its total amount of acid.6Uninjured Henab Turki grapes in different stages of maturity showed an increasing susceptibility to infection byB12cwith advance of maturity. Injured berries of this variety were slightly susceptible to invasion by this fungus even when they were green.7Inoculation results of raw, sterile juice from representative samples of these grapes with cultureB12cshow that a fair amount of growth occurred even on juice from the greenest grapes experimented with. The important role played by the cuticle and cell walls in the protection of grape berries against penetration and invasion respectively byB. cinereawas clearly demonstrated in this experiment.8The hydrogen‐ion concentration and the total amount of acid of grape juice ofpH. 3.0 at the time of inoculation was increased by cultureB12c.Where the hydrogen‐ion concentration of the juice was originally belowpH. 3.0, this concentration, as well as the total amount of acid, was decreased by this fungus.9The changes in the acid reactions of media byB. cinereaare, therefore, dependent upon(a)the variety of this fungus, (b) the initial hydrogen‐ion concentration of the substrate, and (c) the source of ni

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05052.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYBy forced aeration, acid soils can be rendered quite as favourable for the growth, ofOphiobolus graminisalong the roots of wheat seedlings as alkaline soils. This finding is in agreement with the hypothesis that growth of the fungus along the wheat roots in acid soils is retarded by the accumulation of respiratory carbon dioxide.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05053.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYDuring the last few years a newPythiumdisease of tulips has been observed in England, Denmark and Holland, On the Continent the disease is caused byPythium ultimumTrow, whilst in this country the trouble is due to a different species, closely related to, but not identical with,P. de Baryanumvar.PelargoniiBraun. It may be contracted from the soil or carried with the bulbs. ThePythiumcauses a root rot accompanied by dwarfing and lack of vigour in the plants. Sometimes the bulbs and bases of the flowering shoots are attacked and partially or completely destroyed. When this occurs the symptoms closely resemble the more serious Shanking disease due to species ofPhytophthora. Pythiumroot rot has been induced by artificial inoculation and the causal organism has been re‐isolated. Control measures are indicate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05054.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1Methods for satisfactory oviposition studies ofTenebrio molitorL.,Tribolium confusumDuv.,Sitodrepa paniceaL.,Lasioderma serricorneF., andDermestes vulpinusF. are described.2Four types of oviposition cycle are recognized:A. Short‐lived species which lay all their eggs in a few days.B. Long‐lived species laying continuously over a long period.C. Rather short‐lived species laying batches of eggs at short intervals.D. Long‐lived species with two or more periods in which oviposition is more or less continuous, separated by a long period in which there is no oviposition.3The normal oviposition cycles ofLasioderma, Sitodrepa, TenebrioandTriboliumare described.4Records of parthenogenesis in Coleoptera suggest that it is almost confined to the Curculionidae, and even there it is rare. Of the five species studied by the author, no virgin females laid any fertile eggs, and only those ofTriboliumandTenebriolaid any eggs at all.5In many beetles which will copulate more than once, a single mating is sufficient to ensure that all or most of the eggs shall be fertile. In certain species, however, the oviposition rate falls if there are not repeated matings. This is shown to be the case inTribolium, where a second mating, even in females still laying fertile eggs, has a marked stimulatory effect.6There are usually both upper and lower limits of temperature for oviposition. In the experiments onTenebrioandTriboliumit appeared that the upper limit was determined by the temperature which was soon lethal to the beetles; the lower limit lay between 14 and 16°C.7InTriboliumit was shown that a sudden drop in temperature from 27 to 18°C. has a marked stimulatory effect on the oviposition rate of the beetles after they had been returned to 27°C.8The conditions of atmospheric humidity and of food moisture‐content suitable for different species are very varied. Certain species, such asDermestes, must drink water if they are to lay normally.Triboliumcan live, and lay more than half of the normal number of eggs, in a flour and in an atmosphere approaching complete dryness.Tenebriorequires no water to drink, but even in 20 % relative humidity (at 27°C.) oviposition is very greatly reduced.9Certain species, especially those of the short‐lived type, can lay eggs in empty glass tubes in the absence of any food or other oviposition site.Lasioderma.however, though short lived, requires an oviposition site; for this muslin will partially replace food. If it has first been fed on a suitable flour,Triboliumwill lay a few eggs in pure starch, which is not a sufficient food for the development of the ovaries. It will not lay in empty tubes even if it has been fed.10The changes in the appearance of the reproductive organs ofTriboliumduring the life of a female are described. After oviposition the degenerating egg follicles form the so‐called “corpus luteum”. This character is more easy to see when the ovary is empty, for example in a female in which lack of food has inhibited egg formation, than when egg production is continuing actively. It is shown that inTriboliumany external factor which interrupts oviposition will produce an ovarial cycle like that already described in the Scolytidae, in which family the interruption is normally due to hibernation or to the need for special food

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05055.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARYA list of insects found infesting stored products is given, with details of the commodities upon which they have been found.The author is indebted to H. Britten, Esq., F.R.E.S., for the identification of many insects and for much helpful advice and encouragement; also to the London, Midland and Scottish Railway Company for permission to publish this paper.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05056.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

SUMMARY1The toxicity of stomach poisons to sheep maggots was tested under laboratory conditions.2Dipping experiments were carried out with various materials. None of these made the fleece repellent for more than a few days. Arsenic was the only material which rendered the fleece poisonous for an appreciable period.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1937.tb05057.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY