摘要:

This paper reports the results of two years of investigation at the Horticultural Experiment Station at Vineland, Ontario, on fungi associated with the root rot of strawberries. Roots from the field were collected periodically throughout two growing seasons and were studied by direct microscopical examination and by plating methods. Hundreds of isolates from diseased roots were tested by artificial inoculation of strawberry roots, and the primary parasites were further studied. These were classed in the following genera:Pythium,Fusarium,Alternaria,Ramularia,Rhizoctonia,VerticilliumandCylindrocladium. Microscopical examination revealed three additional forms,Asterocystis, a Plasmodiophoraceous fungus and the Phycomycetous mycorrhizal fungus, which are obligate parasites of Phycomycetous type. Some of the fungi occurred more frequently than others, and there were seasonal variations in the activity of most of them. A similar root flora was encountered in wild strawberry roots, so that most of these fungi are probably indigenous. Their relative importance can be determined only by several years of observation of field material.

ISSN:1923-4287    

DOI:10.1139/cjr34-071

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The investigations reported here have centred largely around isolations from, and critical microscopic examination of, the roots of affected plants. Isolations from 684 young, adventitious and lateral roots showing definite lesions bordered by turgid, healthy tissue, yielded representatives of approximately 20 different genera of fungi, ranging in frequency of occurrence from 0.4% in the case ofGliocladiumto 32.7% in the case ofFusarium. Next toFusarium, isolates ofRamulariaandPythiumappeared most frequently and consistently in culture, the former in 28.5%, and the latter in 10.8%, of the plantings. Results of infection experiments involving these as well as other genera, includingPenicillium,Rhizoctonia,Hainesia,Cylindrocladium,ConiothyriumandHelminthosporium, are not yet available and it is impossible at the moment to evaluate the significance of their association with the diseased condition of the roots from which they were isolated. Isolations from 125 apparently healthy rootlets occurring on root systems, other parts of which were more or less severely diseased, yielded representatives of nine different genera of fungi, ranging in frequency of occurrence from 1.6% in the case ofAlternariato 5.6% in the case ofRamularia. Isolates ofFusariumappeared in 4.0% of the plantings.Microscopic examination of 550 adventitious and lateral roots of wild and cultivated plants has revealed the almost universal occurrence in their tissues of two of the so-called "endotrophic mycorrhizal fungi." One of these is of the characteristic phycomycetoid type, producing arbuscules and vesicles, the other, of theRhizoctoniatype familiar in orchids. The former type has been observed much more consistently than the latter. In a number of instances both types have been found in the tissues of the same rootlet. At least three strains of theRhizoctoniatype have been isolated but so far all efforts to culture the other organism have been unsuccessful. Resting spores ofOlpidiaster(Asterocystis) and the spherical, smooth-walled spores of some member of thePlasmodiophoraceaewere observed in diseased rootlets in the early part of the growing season.Pythiumwas noted in abundance occurring on diseased roots obtained in the field during September and November.Nematodes have been encountered in association with diseased roots in numbers and frequency sufficient to suggest a possible causal relationship to strawberry root rot.

ISSN:1923-4287    

DOI:10.1139/cjr34-072

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

not available

ISSN:1923-4287    

DOI:10.1139/cjr34-073

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

Molybdenum, identified spectrographically by the lines 3902.9Å, 3864.1Å, 3798.3Å, 3193.9Å, 3170.3Å, 3158.1Å and 3132.6Å, was found to be present in vetch, alfalfa, alsike, red clover, timothy, goldenrod, reed canary grass, field corn stalks, Canada thistle, ragweed, celery, beets and carrots grown on a farm in Jacques Cartier county, Quebec. Molybdenum could not be detected in the soil on which the plants grew.Molybdenum was not found in vetch plants grown on several farms in Brome, Compton and Sherbrooke counties; nor in timothy, alsike clover or red clover grown on a farm in Brome county; nor in lettuce, celery, cabbage, beets and carrots grown on two different muck soils of the St. Lawrence River valley, in Huntingdon county.The farm in Jacques Carder county lies in the Ottawa River valley drainage basin, the other farms do not. Known deposits of molybdenum occur in the Ottawa River valley.

ISSN:1923-4287    

DOI:10.1139/cjr34-074

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

Methyl cyanoacctate, cyanoacetamide, and malonitrile readily add to vinyl phenyl ketone to give trimolecular products, while nitromethane gives a substance composed of one molecule of nitro compound and three molecules of unsaturated ketone. The reactions of the delta ketonic nitrile formed from the ester are described in detail; it is transformed into reduced pyridine derivatives, and a secondary open chain nitrile. The latter, in turn, is converted into pyridine and hydropyridine derivatives.

ISSN:1923-4287    

DOI:10.1139/cjr34-075

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

A more detailed examination has been made of the kinetics of the methanol decomposition on solid and liquid zinc. The order of the reaction lies between zero and one-half on both solid and liquid. The heat of activation is approximately 30,000 calories per gram molecule. The reaction is mainly dehydrogenation.Unsuccessful attempts to investigate certain other reactions on liquid metals are described.

ISSN:1923-4287    

DOI:10.1139/cjr34-076

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

The effect of drying, in air containing one and two parts of sulphur dioxide per million, cotton fabric wetted with solutions such as those which it would encounter in power laundry rinse waters has been investigated. Factors such as sulphur dioxide concentration, humidity, temperature and light have been examined and kept under all possible control. The sulphur dioxide has been found to have little or no effect in producing deterioration of the fabric.

ISSN:1923-4287    

DOI:10.1139/cjr34-077

出版商:NRC Research Press    

年代:1934

数据来源: NRC

摘要:

Little quantitative information being hitherto available concerning the degree of restraint developed at the ends of steel beams and girders with welded connections, and the extent of possible related economies and improvements in frame stiffness being correspondingly uncertain, the experimental investigation of two distinct aspects of joint rigidity was undertaken. These were:(a) The relative capacity under gravity load of beam-girder and beam-column connections for developing beam restraint, or continuity, designed with a view to reducing the required weight of the connected beam.(b) The relative values of certain typical connections in resisting the deformation of a frame due to lateral loads, either in one direction or subject to reversal.Two series of specimens were fabricated and tested in relation to plain rating beams. The first series, designed for the purpose of studying beam continuity, consisted of ten 9-in., 20.5-lb. Bethlehem beam double-cantilever specimens, employing five different types of welded connections. The second, designed primarily for the study of wind bracing rigidity, consisted of twelve 18-in., 47-lb. Carnegie beam double-cantilever specimens with three different types of connections. These types included the welded T, the welded gusset and, for comparison, the riveted T. For half the specimens of the second series the connections were to a central transverse plate simulating the web of a column, and for the other half to the flanges of a 12 by 12-in., 110-lb. H-column.Coefficients of restraint, that is, the ratio of actual to 100% restraint, were ascertained by determining end slope angles with the aid of a special type of longitudinal extensometer attached to the beam flanges. Although, for convenience, the specimens were tested as double-cantilevers the results were readily transformed to be applicable to the partially restrained beams simulated by the specimens.Story drift angles, that is, the angle through which the columns of a building subjected to horizontal force would tilt in one story of height due to the deformation of the connections, were ascertained by utilizing the end slope angles mentioned above and the observed deflections of the specimens. The results for the specimens were transformed by calculation to be applicable to a 20-ft. bay of an actual building.Broadly stated, the results obtained in the study of the connections tested were:(1) Welded connections as ordinarily designed for end restraint fall short of the ideal value of 0.75 for the coefficient of restraint by from 10 to 25%.(2) Both welded and riveted connections designed primarily for capacity wind moment develop a coefficient of restraint in excess of the most economical value (0.75) required to resist gravity loads only.(3) A beam welded to a column web may develop less story drift angle than would a plain beam integral with the column. T's riveted to a column flange may, for a 20-ft. bay, give rise to a lineal drift of as much as 0.36 in. per 12-ft. story under a capacity wind in one direction, while welded T's under the same conditions showed 0.09 in. and welded gussets only 0.03 in.(4) In the connections designed for beam continuity only, the compression attachment was in all cases more yielding than the tension one. Transfer of axial compression by longitudinal welds to the edges of a thin flange introduces much yield due to horizontal shear in the flange.(5) In wind connections either to a column web or to a column flange, the top and bottom attachments, under capacity reversing load, gave approximately equal total longitudinal deformations for each of the three types.(6) From a third to a half of the flexural slope in a connection to an unstayed column flange may be charged to the deformation of the column flange.(7) In wind connections to an unstayed column flange the welded connections gave regional flexural slopes from 17 to 63% of the corresponding ones developed in the riveted T-connections, depending on the region, or longitudinal zone. Consequently, the welded connections were definitely stiffer than the riveted ones in all regions.(8) The aggregate longitudinal elastic deformation in tension for capacity reversing load was greater than the aggregate deformation in compression, the maximum excess being 70%. This was for the riveted T-connection to a column web.(9) For the riveted T's a large part of the longitudinal deformation was non-elastic slip. It amounted to 31% for the connection to a column web and 46% for a connection to a column flange.(10) Welding of stiffeners to the column flanges reduced the longitudinal deformation of the welded T and the welded gusset connections to 75 and 85% of their previous values, respectively.(11) For the specimens designed for beam continuity only, the ratios of the test factor of safety to the design factor of safety, based on an estimated ultimate strength of 10,000 lb. per lineal inch of-in. fillet weld with uniform distribution of stress, varied from 0.65 to 0.97.(12) For the specimens designed primarily as wind connections, the ratio of test factor of safety to design factor of safety, based on assumed uniform stress distribution, varied from 0.88 to 0.98 for the riveted specimens, from 0.49 to 0.83 for the welded T-specimens and from 1.06 to 1.29 for the welded gusset plate specimens. It is thus evident that non-uniformity of stress, which obviously existed to a marked degree for the welded T-connections, may cause the capacity of certain types of connections to fall considerably below that estimated on the basis of uniform distribution.

ISSN:1923-4287    

DOI:10.1139/cjr34-078

出版商:NRC Research Press    

年代:1934

数据来源: NRC