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In Colima, Mexico, we conducted 8-night mark–recapture grid studies of southern pygmy mice ( Baiomys musculus (Merriam, 1892)) in January 2003–2007 in dry deciduous and tropical moist forests. For 40 000 trap-nights, 436 individuals were captured 764 times (comprising 18.6% of small mammals). The male:female ratio was 1:1.37, 82.9% were adults, 51.4% of females were pregnant or lactating, and coastal animals, on average, were heavier than those inland. Females moved farther than males. Baiomys was on 17 of 25 grids (densities 1.82–106.24 individuals/ha). Moon illumination did not affect capture or recapture probabilities, but trap-night did (overall, probability increased 1.66%/night). Grids with Baiomys had less bare ground and a more open canopy. Capture sites had more grass, less dead wood and bare ground, a more open and lower canopy, and greater distance to trees. Logistic regression indicated coastal capture sites had more forbs, grasses, and woody plants, and thicker vegetation at 1 m height with trees being relatively distant. Variables differed somewhat for northern sites, and the equation for all grids included 10 of 14 environmental variables. Baiomys frequented edge of an unimproved road traversing one grid. Baiomys musculus, widespread in Colima, exhibited preference for habitats with relatively dense ground cover and at least a partially open canopy.

The hydraulic properties of a peat used in a commercial peat biofilter were evaluated to determine their relationship with density and to establish a time domain reflectometry (TDR) calibration curve for water content as a function of the measured dielectric constant. The peat studied was a milled Sphagnum peat with a high organic content (99%). The dry densities evaluated in this study ranged from 90 to 180 kg/m3. The saturated hydraulic conductivity (Ks) decreased with an increase in dry density (ρdry) and was found to follow a log-linear relationship (Ks = 0.2462 exp(–0.0438ρdry), correlation coefficient R2 = 0.9789). As expected, the soil moisture curve was impacted by density, with a higher density resulting in higher water contents for a given suction. The data were fit to the van Genuchten relationship. A TDR calibration curve was generated at five different densities. A comparison of the curves indicates that the water content as a function of dielectric constant was not dependent on density because of the significantly larger dielectric constant (Ka) of water compared with those of peat solids and air-filled voids. The TDR calibration curve for the peat evaluated in this study (volumetric water content Θv = 0.2667 ln(Ka) – 0.1405, R2 = 0.9564) predicted higher water contents for a given dielectric constant compared with those from similar calibration curves for peat published in the literature. The data were compared with those from six other studies and indicated that the TDR calibration varied for different organic soils. The density-dependent hydraulic parameters and TDR calibration curve are important parameters needed to study the hydraulics of peat biofilters.Key words: peat, TDR, time domain reflectometry, density, hydraulics, soil moisture.

Peat filters have been used to treat septic tank effluents from domestic and commercial sources, landfill leachate, and acid mine drainage. A better understanding of the hydraulics and impact of the organic loading on these types of systems will enhance the application of peat filter systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Ontario, Canada. The filter was instrumented with tensiometers and transducers to monitor the pore-water pressures in response to a pulse of septic tank effluent. Samples of peat were collected to determine the dry density profile with depth. The soil moisture retention curve, effective porosity, and hydraulic conductivity as a function of dry density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. Two model scenarios were evaluated to demonstrate the impact of density variations on model simulations. Model simulations that accounted for dry density variations with depth measured in the field more accurately simulated the pressure responses measured in the field.Key words: unsaturated flow, peat, filters, septic, modelling, density.

Populations of western burrowing owls (Athene cunicularia hypugaea) are declining. In the Great Plains this decline maybe related to a decline in black-tailed prairie dog (Cynomys ludovicianus) towns that the owls use for nest sites. One potential cause of prairie dog decline is conversion of native prairie to agriculture. We predicted that owl-occupied prairie dog towns would be in less fragmented landscapes that contain more prairie then owl-unoccupied prairie dog towns. To test this prediction, we used a geographic information system and spatial analysis metrics to examine the landscape within 1000 and 2500 m radius circles surrounding prairie dog towns in the shortgrass prairie in northeastern Colorado. We compared landscape features of irrigated cropland, non-irrigated cropland, and shortgrass patches around owl-unoccupied (N = 7) and owl-occupied (N = 15) prairie dog towns at these two spatial scales. Contrary to our predictions, at the 2500-m scale burrowing owls prefer to nest in towns surrounded by a landscape in which shortgrass patches were a smaller percentage of the total landscape, relatively far apart from other shortgrass patches, and more numerous then crop patches. At the 1000-m scale owls nested in towns in which shortgrass patches were a smaller percentage of the total surrounding landscape. In Logan County owls may select nest sites in prairie dog towns in more fragmented landscapes because prey availability maybe higher than in less fragmented landscapes and (or) prairie dog control programs may be more active on shortgrass rangelands than in croplands. In addition, the level of fragmentation in our study area (62% of the study area is occupied by native grassland) may not be high enough to have negative consequences on nest occupancy of burrowing owls. However, it is difficult to generalize about the effects of landscape fragmentation on burrowing owls because any effects are probably a complex function of local habitat structure, landscape structure, and local prey and predator availability.

The conceptual basis of the seismic design procedure in the National Building Code of Canada is reviewed. The design earthquake is specified only for the ultimate limit states at which the performance of both ordinary and important buildings is evaluated by an elastic static analysis in all zones. Criteria for checking the serviceability limit states, which apply to moderate earthquakes that may occur relatively frequently in the life of the building, are not specified explicitly. It is suggested that the current design approach could be improved by adopting a design strategy that addresses as well the serviceability limit states and associated evaluation criteria and gives methods for design and analysis as a function of the seismic zone and the importance of the structure. An earthquake with a return period of 1 in 50 years is proposed tentatively for the serviceability limit states with appropriate drift limits. The proposed serviceability limit states are shown to govern the design of buildings for values of the force modification factor greater, on average, than 3.Key words: analyses, earthquake, seismic design, serviceability limit state, steel, ultimate limit state.

The seismic performance of two-storey steel buildings with concentrically braced frames as the lateral load resisting system is evaluated. The buildings are designed in accordance with the National Building Code of Canada (1995) and CSA Standard S16.1-94 for five seismic zones in western Canada. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the buildings are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the shear strength of the roof diaphragm, and the stiffness and strength contributions of the nonstructural partitions. The seismic response is estimated with nonlinear static and dynamic time history analyses. Roof diaphragm flexibility does not influence the dynamic behaviour significantly. The distribution of lateral forces from response spectrum analysis agrees well with that specified. Current design procedures provide reasonable estimates of the lateral drift in low and moderate seismic zones. Brace ductility demands are reasonable and may be limited due to the contributions of nonstructural partitions. However, in moderate and high seismic zones, the connections, beams, columns, and roof diaphragm are overloaded. The capacity design procedure is recommended to provide adequate resistance to the overloaded components.Key words: analyses, capacity design, concentrically braced frame, diaphragm, dynamic, earthquake, low-rise, nonlinear, seismic design, steel.

The seismic performance of single-storey steel buildings, with concentrically braced frames and a roof diaphragm that acts structurally, is evaluated. The buildings are designed in accordance with the National Building Code of Canada 1995 and CSA Standard S16.1-94 for five seismic zones in western Canada with seismicities ranging from low to high. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the building are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the strength and stiffness contributions of the cladding, and the flexibility, strength, and distributed mass of the roof diaphragm. The seismic response of the models is assessed by means of a linear static analysis, a response spectrum analysis, a nonlinear static or "pushover" analysis, and nonlinear dynamic time history analyses. The results indicate that current design procedures provide a reasonable estimate of the drift and brace ductility demand, but do not ensure that yielding is restricted to the braces. Moreover, in moderate and high seismic zones, the roof diaphragm responds inelastically and brace connections are overloaded. Recommendations are made to improve the seismic performance of such buildings.Key words: analyses, concentrically braced frame, dynamic, earthquake, flexible diaphragm, low-rise, nonlinear, seismic design, steel.

The effect of brace overstrength on the seismic response of a single-storey steel building with concentrically braced frames (CBFs) and a roof diaphragm that acts structurally is assessed by comparing the dynamic response of the building without overstrength to that of one with significant overstrength. Four structural idealizations are used that differ in modelling of the roof diaphragm and the CBFs. Dynamic response is obtained by time history analyses of the models with an appropriate set of 20 historical earthquake accelerograms scaled to zone 4. An oversupply of strength and stiffness increases the seismic demand on the building. The response is significantly influenced by the model used. Columns and brace connections of the CBF are overloaded if the diaphragm is considered to be rigid and its limited shear connection strength ignored. When this connection strength is considered, the ductility demand is localized at the connection and consequently the CBF is not overloaded. Similar results are obtained with a model that accounts for the distributed mass and flexibility of the diaphragm and its shear connection strength. The study emphasizes that designers should consider the strength and stiffness of all elements in the lateral load path. Implications for seismic design and rehabilitation analyses are discussed.

The facility performance requirements for the Confederation Bridge specified that the bridge be designed using load and resistance factors developed specifically for the site. This paper reviews the derivation of these factors for both the ultimate limit states and the serviceability limit states.

Even though the design of corrugated steel plate culverts is based on compression ring theory, soil-steel structure interaction will likely lead to the development of bending moments in the steel plates. Successful application of these structures requires that these moments be accommodated without distress, while the plate carries axial thrust. This requires ductile flexural behaviour.The results of 13 flexural tests, with two-point loading, on lap joints of 3, 5, and 7 mm thick corrugated steel plates, as well as one test on plain 5 mm thick corrugated steel plate, are reported. Bolt configurations consisting of 2, 3, and 4 bolts per complete corrugation were tested to investigate the postulate that lap joints subject to bending moments can be made in a correct or incorrect manner. Correct lap joints are those that do have a bolt near the edge of the lap on the tension side where prying tends to occur, that is, where the gap between the lapped plates tends to open up when the joint is subject to moment. Incorrect laps do have a bolt at this location. Laps with 2 bolts are either correct for both positive and negative bending moments or incorrect for both. Statistically, laps with 3 bolts will be incorrect 75% of the time and laps with 4 bolts all the time.The tests confirm the postulate and show that, in the incorrect laps, tearing of the corrugated plates, starting at the edges of the bolt holes in the critical location where there is prying, occurs shortly after the maximum moment is reached. The tearing leads to a reduction in the moment resistance and reduced ductility even though the maximum moment for incorrect laps may be comparable to that for correct laps. Correct laps exhibit tremendous ductility, achieving joint rotations of 0.4 radians or more. Laps with 4 bolts per corrugation are weaker flexurally than laps with 2 bolts per corrugation because the critical net area on the tension side is less. Shaped washers placed under the bolt heads at the critical location do not improve the behaviour. Inadequate torquing in the bolts leads to increased flexibility, and reduced strength of the lap joints and increased opening of the gap between the plates. Key words: bolted, corrugated, culvert, ductility, flexure, joints, lap, moment resistance, plate, steel, tearing.

The behaviour of cantilever-suspended span systems is influenced by the type of loading and the presence of flange restraint. An experimental program consisting of 33 full-scale tests was undertaken to examine the stability of beams in a single overhang configuration. The results indicate that torsional flange restraint significantly enhances the buckling resistance and is particularly effective when combined with a web stiffener. Lateral bracing of the bottom flange at column supports is of considerable importance in maintaining stability. Simulating the proper boundary conditions is essential, since test specimens are very sensitive to unwanted restraints and can buckle in a higher energy mode.A finite element model was developed that takes into account inelastic material behaviour, residual stresses and cross-sectional distortions. The predicted buckling capacities are in good agreement with experimental results. Key words: cantilever-suspended span, steel beams, distortional buckling, flange restraint, inelastic behaviour.

The genetic variability of gray wolves (Canis lupus) from northwestern Canada was assessed through starch-gel electrophoresis. Of 27 protein systems examined, 25, representing 37 presumptive loci, were consistently scorable; 7 proteins (5 were consistently scorable) exhibited polymorphism. The level of heterozygosity (3.0%) was medial relative to values reported for natural populations of Carnivora and high relative to values reported for natural populations of canids. An overall pattern of few deviations from Hardy–Weinberg expectations and some spatial heterogeneity was observed. Wolves associated with different caribou herds exhibited a low level of differentiation (FST = 0.029). The pattern of variability supports the view of a large panmictic population resulting from extensive movements of individuals and packs and from natural and human impacts on pack structure and formation.

The beam–column interaction equations of the Canadian Standards Association Standard CAN3-S16.1-M84 "Steel structures for buildings — limit states design" are reviewed and areas of concern in the formulations are addressed. The interaction equations developed for the 1989 edition of the standard, CAN3-S16.1-M89 "Limit states design of steel structures," and the methods of dealing with the areas of concern in the previous standard are presented. The new standard requires that at least an approximate second-order geometric analysis be carried out. For frames dependent on the frame stiffness for lateral stability, no longer is the traditional method, using effective length factors greater than one, allowed. Unlike the current American Institute of Steel Construction "Load and resistance factor design'' (AISC LRFD) specification, two sets of interaction equations, one for in-plane member strength and the other for out-of-plane stability, are used. This results in considerably less unnecessary conservatism. In both sets of interaction equations, the component of the moment due to translation is increased by the second-order effects. The "double ω" problem has been resolved and the minimum sway effects for the gravity loading case have been increased substantially to guard against sidesway buckling. A design example using the new standard is given. By means of a series of analytical examples, the requirements of S16.1-M89 are compared with the traditional method of S16.1-M84. For frames with direct-acting bracing, S16.1-M89 gives interaction values about 1.15 times those of the previous standard with a coefficient of variation of 0.08, while for unbraced frames the corresponding values are 0.98 and 0.07. The S16.1-M89 values reflecting greater rigor in a number of areas are considered the more valid. The S16.1-M89 standard would give comparable results to the AISC LRFD specification for class 1 sections when out-of-plane behaviour governs. The latter specification does not specifically cover cross-sectional strength and in-plane behaviour as does S16.1-M89. Key words: beam–column, stability, strength, bending, compression, standards.

When the method of sectioning is used to determine the relaxation of residual strains, coupons are cut from the cross sections. Variations in the longitudinal residual stresses through the thickness frequently cause the coupons to curve on sectioning. For example, hollow structural sections may be formed by first bending a plate in circular form and welding the edges together longitudinally. The bending process results in circumferential through-thickness bending stresses varying from tension on the outside to compression on the inside. Away from the ends of the member the restraint to the development of Poisson strains causes longitudinal stresses varying from tension on the outside to compression on the inside. The relaxation of these on sectioning causes the coupon to curve concave outward. Relaxation strains measured on the chord will be in error and corrections must be applied. The three errors that result (Galambos 1988) are 1. measurement of the final gauge length along the chord between gauge holes rather than along the arc length in the plane of the surface

In the natural environment and in culture the vegetative mycelium of Fomitopsis cajanderi forms a primordial mat, a basidiocarp primordium, and a sporulating basidiocarp. The fundamental structural unit is the clamped, generative hypha which functions initially in nutrient absorption, then produces unbranched or branched skeletal cells and basidia. and later develops irregularly thickened walls and swollen clamp connections. These structural elements, the brownish-rose color produced by massed skeletal cells, the hymenium of basidia only, and the narrow, slightly curved basidiospores are characters readily observed in the natural basidiocarp and in culture.

The authors previously established that an initially flat rectangular steel plate, clamped on all four edges, displays three modes of behaviour as the intensity of a distributed transverse load increases: elastic flexural-membrane action, inelastic flexural-membrane action, and inelastic-membrane action.For a long narrow plate, elastic flexural-membrane action exists up to the load at which yielding of the extreme fibres along the long edges occurs. Subsequent plastic hinge formation along the long edges reduces the stiffness. The second stage ends with complete yielding in tension along the long edges. From this point onward, the plate acts essentially as a membrane straining inelastically as yielding gradually progresses from both edges toward the centre. A lower bound to this behaviour is obtained by assuming that Poisson's ratio is the elastic value and the maximum membrane stress is the yield stress. A higher lower bound is obtained using the plastic value of Poisson's ratio. The load–deflection curve gradually moves from the lower value to the higher and, because the edge forces can exceed yield, will finally exceed the latter, as confirmed by tests.A finite element program modelling plane stress conditions, the inelastic Poisson's ratio, and the stress–strain behaviour to failure gave a load–deflection response closely following the three predicted regions of behaviour. Two failure criteria have been established: a limiting tensile strain due to bending and tension at the edge and the shear resistance there. The behaviour and failure loads have been confirmed by two tests. Strain measurements taken during the tests substantiate, in general, the predicted behaviour.Implications of using the ultimate strength of plates for the design of offshore structures for oil exploration and production in the Arctic are presented. Key words: deflection, design, finite elements, inelastic, membrane, plates, steel, strains, stresses, transverse load, ultimate strength.

Interfertility tests between Alberta collections identified as Coriolus hirsutus, C. pubescens, C. velutinus, C. zonatus, and C. versicolor have shown that there are only two distinct species of this complex in Alberta, each with a range of morphological variation. Both these species, which are being called Coriolus hirsutus and C. pubescens, have the tetrapolar type of fertility. Isolates of basidiocarps from Sweden identified as Coriolus hirsutus were intersterile with Alberta isolates of this species, which suggests the existence of two different species. Cultures of C. versicolor (Ontario) were unilaterally dikaryotized by C. hirsutus and to a lesser extent by C. pubescens, indicating very close relationship. Dark pigment lines frequently formed between paired isolates of both distantly related and closely related cultures, indicating that it is not mating-type factors which control pigment formation in the contact zone.

A detailed statistical analysis to give ratios of mean to nominal values and associated coefficients of variation (based on raw data collected from Canadian mills on the strength and geometric properties of rolled W shapes, welded W shapes, and class H hollow structural sections) is presented. By relating the tested capacity (based on physical tests performed by others) to the predicted capacity (based on the design equations in CSA standard S16.1-1974, Steel Structures for Buildings—Limit States Design), the professional ratio and its associated coefficient of variation were determined for steel columns as a function of the slenderness ratio, as well as for laterally supported and laterally unsupported steel beams, enabling the performance factor to be determined for these members over the entire range of behaviour. A serviceability criterion for steel bridges is presented.

The economic design of steel caissons for drilling and production platforms in the Arctic Ocean, formed from steel plates and supported by a rectangular grid of stiffeners, beams, and girders, requires that the full strength of the plates be mobilized to withstand extreme ice forces. A comprehensive method of analysis is needed to describe the behaviour of continuous steel plates into the inelastic range when they are acted upon by transverse loads. From this analysis, design procedures could then be developed.An extensive literature search has not revealed that satisfactory solutions exist for the load–deflection response of transversely loaded flat plates beyond the elastic limit when both flexural and membrane action are taken into account. Experimental data available in the inelastic range of behaviour are also limited.By considering various limiting simplified behavioural modes for the load–deflection response of uniformly loaded flat plates of zero aspect ratio, possible load–deflection domains are established. The limiting responses investigated are: elastic–inelastic flexural action, elastic membrane action, inelastic membrane action with increased stiffness resulting from increased Poisson's ratio in the inelastic range, elastic flexural membrane action, and action of a fully yielded cross section in flexure that gradually gives away to a fully yielded cross section in tension. Within the domain so established, a load–deflection behaviour is proposed that is in reasonable agreement with the results of the limited test data available. The results of a finite element analysis using the ADINA computer program are also in reasonable agreement with the proposed analysis. Design applications are discussed. Key words: deflection, elastic, elastoplastic, flexural resistance, membrane force, membrane resistance, plates, steel, strains, stresses, transverse load.

A series of notched static tension tests was carried out over a range of temperatures to study the influence on the fracture behaviour of a medium strength steel of such parameters as the width of the specimen, the depth of the notch, the thickness of the specimen, the notch location, the root radius of the notch, and residual stresses. Based on these tests, the concept of strength interaction surfaces has been developed. The major portion of such a surface, called the strength cirque, determined empirically, was found to be dependent on the temperature, notch depth, and specimen width and thickness. Strain rate and residual stresses are also expected to affect this surface.From the strength interaction surfaces, the critical flaw size can be estimated as a function of such parameters as temperatue, member width, and thickness, to satisfy the criterion that, at the lowest operating temperature, general yielding of the member at an unflawed section should occur prior to fracture across the flawed section in series with it. Thus a procedure is proposed to prevent the fracture in service of medium strength structural steel (up to 350 MPa yield strength) members containing flaws and subject to low ambient temperatures (down to −60 °C).

Germination of basidiospores in Fomes fomentarius (Fries) Kickx is bipolar with germ tubes emerging at both ends. Ungerminated spores are smooth with a thick cell wall consisting of two layers: an outer thin, electron-dense layer and an inner thick, electron-light layer. During the early stage of germination, two additional cell wall layers are formed: a very thin, electron-dense layer and a relatively thick, electron-light layer. Germ tube walls originate from these newly formed, inner layers. Ungerminated spores are uninucleate and contain numerous lipid bodies, ribosomes, and cisternae of endoplasmic reticulum. Germinated spores have distinct mitochondria and an invaginated plasma membrane and are usually devoid of endoplasmic reticulum.

Genetical and developmental studies support the conclusion that Hirschioporus pargamenus (Fr.) Bond. & Sing. and H. subchartaceus (Murr.) Bond. & Sing. are distinct but closely related species. Paired monokaryotic isolates from each species were almost completely intersterile and produced lines of demarcation containing peculiar clasping hyphae. Distinctions were found in basidiospore size and in the macrostructure and microstructure of the margin, context, upper surface, and hymenial surface of natural basidiocarps. In culture, clear distinctions were observed in hymenial configuration of basidiocarps and spore size.

An oligotrophic and a eutrophic lake in Alberta were comparatively investigated for 14 months to elucidate relationships between the physicochemical environment and the species composition, seasonal succession, vertical distribution, and seasonal cycles of their phytoplankton. One hundred and seven algal species were found in Muir Lake and 63 species in Hastings Lake. Increases in the numbers of Anabaena flos-aquae accompanied decreases in the numbers of several green algae, viz Pediastrum and Scenedesmus spp., suggesting antagonistic effects. Three groups of vertical distribution patterns of phytoplankton occurred in both lakes: buoyant and some motile forms accumulated at or near the surface, a second group was more or less uniformly dispersed throughout the water column, and a third group occurred only in bottom waters. Intermittent species were classed as either stenochronic or eurychronic, depending on the length of their pulses. In Muir Lake, Asterionella formosa was inversely correlated with silica concentrations. Dinobryon increases were associated with increases in phosphates and bicarbonates. Up to 5 times more orthophosphate occurred in the ice than in the water beneath. Ice may be of heretofore unrealized ecological significance as a phosphate reservoir for the spring aquatic community.

On the evidence of titration with 2,6-dichlorophenolindophenol, the newly ripe hips of Rosa acicularis contain 1800 to 3500 mg. % ascorbic acid in the wet flesh or about 4.5 to 7.6% ascorbic acid on a dry basis. The corresponding values for R. woodsii and R. arkansana are 1300 to 2000 mg. % or 4.0 to 6.0%. The hips of R. acicularis are the richest of the wild roses. The hips from cultivated roses have usually less ascorbic acid than the wild varieties with the exception of R. laxa, the richest examined, with 3000 to 4000 mg. % in the wet flesh or 8.0 to 10.3% on a dry basis.The ascorbic acid in rose hip extracts is remarkably stable to heat and oxidation, and methods are indicated for the preparation of products suitable for winter food supplements.The leaves and bark of wild rose bushes commonly contain 300 to 500 mg. % ascorbic acid in the fresh matter, and the petals 20 to 70 mg. %.

This paper is a survey of the ascorbic acid content of native Alberta fruits. Some wild fruits that are not usually eaten have been included in the investigation. The values of vitamin C for the most widely occurring and most generally used wild fruits are: blueberries, 5 to 18 mg.%; chokecherries, 5 to 19 mg.%; high-bush cranberries, 8 to 51 mg.%; pin cherries, 8 to 34 mg.%; raspberries, 14 to 40 mg.%; and saskatoon berries, 5 to 38 mg.%. These afford a considerable source of ascorbic acid.In an addendum there are given the ascorbic acid values in miscellaneous plant materials.

The ascocarp of Apiosporina collinsii is a pseudothecium which develops from a subiculum. It has pseudoparaphyses, bitunicate asci and an irregular pore in the apical region. The centrum development is of the Pleospora-type and the production of ascogenous hyphae is similar to that described for Spororomia leporina. Apiosporina collinsii is classified in the Venturiaceae, Pleosporales and Loculoascomycetes.The restriction of the parasite to one or a few branches of the host Amelanchier alnifolia is due to the production of cork cells which isolate infected areas in the stem. The retention of infected leaves is associated with cork which surrounds the leaf traces in the petioles.