ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05952.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05953.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.11. At maturation, the first instar larva commences to feed upon the residual‐yolk‐mass contained in the anterior part of the egg, remaining within the chorion to do so. It takes three to five days to accomplish this. It sometimes eats a few particles of the walls or contents of the vessel before settling down to moult.2From seven to ten days after reaching maturity the young larva undergoes an ecdysis and then commences its boring operations in the w

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05954.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.11. Under ordinary environmental conditions of temperature and sunlight the growth of peas, as of barley, is seriously hindered by overcrowding, even when each plant receives a similar supply of food and water. Not only is less dry weight produced, but the pods become thin and distorted and fail to develop their seeds properly.2Growth tends to be depressed in hot sunny weather when no protection is afforded. The chief detrimental factors concerned appear to be high temperatures at the roots associated with strong and prolonged sunshine, though the two factors acting individually are much less potent for harm. Under these conditions crowding shelters the roots from overheating and the leaves from too much sunlight, and up to a certain point crowded plants make better growth than those spaced well apart. Overcrowding, however, still depresses growth, probably because the light and root temperature reductions are too great.3Provided insolation is not excessive the amount of daily fluctuation of root temperature over a total range of about 22oC. (6–7‐28‐9oC.) has comparatively little influence upon growth; high maxima and low minima give similar results to low maxima and relatively high minima, provided the average mean temperatures are not too dissimilar.4With high root temperatures a difference in the degree of insolation or in the angle of incidence of the sun's rays may have a considerable influence on growth, a slight easing off of the solar conditions enabling much better growth to be made.5With very strong sunshine reduction of high maximum root temperatures (from 29oC. upwards) allows of satisfactory growth, when unprotected plants are rapidly killed. The inhibitory action of too high temperatures at the roots is thus clearly shown.Nevertheless, the growth so made is less good than under more normal conditions of insolation, thus demonstrating the harmful action of too powerful sunlight, when all the root temperatures rule high.6Boot temperatures appear to be of greater importance than atmospheric temperatures, as good growth can be made in hot atmospheres provided the roots are kept relatively cool.7There is some reason to believe that the minima are of as much importance as the maxima,i.e.that plants can withstand very high maximum temperatures provided there is a considerable drop to the minima, but cannot put up with the constant conditions of heat induced by fairly high maxima, and high

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05955.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.1The Stripe Disease and the Grand Rapids Disease of tomato are distinct diseases caused by two bacterial parasites,Bacillus lathyriandAplanobacter michiganense.2The yellow organism,Aplanobacter dissimulansn.sp. (Paine and Bewley), which is frequently found associated withBacillus lathyriis not identical withAplanobacter michiganense.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05956.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05957.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.11. For bacterial count work the first essential in a medium is that it should be uniform and reproducible in its results.2In the medium here described, details of which are given on p. 271, reproducibility has been achieved by the use of pure chemical compounds in an agar medium and by selection of such constituents as will not produce a significant change of reaction during sterilisation.3On agar media, surface spreading colonies interfere with the accuracy of the results. A special study was made of a common spreading organism,B. dendroides.This organism spreads by active motility, and the factors controlling its spread were found to be (1) the existence of a surface film of water on the agar, and (2) the rate of multiplication previous to the drying of this film. A medium was developed on which this rate of multiplication was greatly reduced and on which, consequently, spreading is greatly restricted.4Tests of the medium have shown that the results obtained with it are uniform and can be reproduced in different batches of medium.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05958.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.The infection of apple trees by the canker fungus through scab infections is described.The conidia alighting on the exposed scab stroma give rise to a mycelium which attacks the latter and then grows out into the cortex. The fungus is able to pass through any immature cork layer and finally reach the wood.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05959.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

摘要:

Summary.11. Samples of soil were taken from two of the plots at the Rothamsted Experimental Farm and all insects and other invertebrates were recorded together with the approximate depths at which they occurred.2One of these plots (plot 2) has received 14 tons of farmyard manure per acre per annum since 1843; the other (plot 3) has received no manure of any kind since 1839. This difference in treatment had a very marked effect on the number of insects present.3Twenty‐three samples of soil were examined from each plot, each sample being a cube 9 times 9 × 9 inches. The soil in each sample was removed in five layers, so that it was possible to determine the approximate depth at which the specimens occurred.4There were, in round numbers, 15,100,000 invertebrates per acre, of which 7,720,000 per acre were insects, in plot 2, and 4,950,000 invertebrates per acre, of which 2,470,000 per acre were insects, in plot 3.5The greatest number, both of insects and of other invertebrates, occurred in the upper three inches of the soil, but some species were found in larger numbers at a greater depth, the greatest number ofElateridaelarvae being found at a depth of five to seven inches, and ofSymphylaat a depth of seven to nine inches.6Some species, such as the larvae ofChironomidaeandTrichocera, were practically confined to the plot which had received farmyard manure, plot 2, while other species, such as theCollembola, Onychiurus ambulantandO. fumctarius, although they occurred in both plots, were considerably more numerous in plot 2.7Injurious insects, such as the larvae ofElateridae, TipulidaeandHepialidae, appeared to be little affected by the different manurial treatment of the two plots, and occurred in practically equal numbers in the two plots.8Although 198,653 and 164,983Elateridaelarvae per acre occurred in plots 2 and 3 respectively, they did not produce any appreciable effect on the crop.9An attempt was made to estimate the amount of nitrogen contained in the bodies of the soil fauna, and it was found to be 7349.6 gm. or 16.2 lbs. and 3409.2 gm. or 7.5 lbs. in plots 2 and 3 respectively. It is unlikely that there is any appreciable loss of nitrogen from the soil due to the migration of winged members of the fauna.10The worms, insects and insect larvae are beneficial in loosening the soil and facilitating aeration and drainage.11The net results of these observations show that, although the introduction of farmyard manure greatly increases the invertebrate population of the soil, the latter organisms are saprophagous and are not directly injurious to the growing crop. Such injurious organisms as are present occur in approximately equal numbers whether the land be manured or not. The most notable exception to this generalisation is met with in theDiplopoda, whose numbers are increased by about 200 per cent in the manured pl

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05960.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1922.tb05961.x

出版商:Blackwell Publishing Ltd    

年代:1922

数据来源: WILEY