Nosema whitei, a microsporidan pathogen of some species of Tribolium : I. Morphology,life cycle,and generation time

The morphology of Nosema whitei is described from 4 host beetles, Tribolium castaneum, T. confusum, T. anaphe, and Oryzaephilus surinamensis. The effect of host species on the sizes of the various stages was small. The predominant schizogonic stages were mononuclear (26%) and binuclear (73%) although schizonts with up to 5 nuclei were seen. In stained preparations the schizonts were approximately 2.7–7.0 μ in diameter. The sporonts, which do not divide, were elongate (5.6 × 3.1 μ), and had 1 or 2 nuclei. Both the sporoblast (4.2 × 2.2 μ) and the spores (3.5 × 2.0 μ) were binucleate. Fresh spores averaged 4.6 × 2.9 μ. The polar filament length ranged from 75 to 135 μ (mean = 112 μ). The only tissue found infected was the fat body. Host species, dose, and temperature were all found to affect the generation time, which ranged from 8 to 17 days.     

An Intranuclear Microsporidium Associated with Acute Anemia in the Chinook Salmon,Oncorhynchus tshawytscha1

An intranuclear microsporidium is described from hemoblastic cells of the chinook salmon, Oncorhynchus tshawytscha. The infection is associated with an acute anemia in the fish. Up to 47% of the hemoblast nuclei were infected in anemic fish. The organisms, found only in spleen and kidney tissues, were 1–2 μm in diameter and consisted of vegetative and early sporulation forms. This microsporidium differs from known species which parasitize fish in its tissue location; however, the absence of mature spores and other life cycle stages precludes determination of its precise taxonomic identity.     

Relationship of the DNA content in the nuclei of Amoeba proteus to the food regimen]

The relative DNA content of isolated Amoeba proteus nuclei has been measured by cytofluorometry. With the amoeba strain studied, the generation time is roughly equal to 48 hours at 25 degrees C, and with the presence of food in the medium. After the synchronous divisions, amoebae were maintained in the medium either with or without food organisms (Tetrahymena pyriformis). DNA contents in the nuclei of both the amoebae groups were measured within 4 and 48 hours after division. Before 16 hours, the nuclear DNA contents did not differ in either group. Starting from 20 hours, the DNA amount in fed amoebae exceeded that in starved animals. On the whole, the differences in DNA quantity increased by a 48th hour after division, when the nuclei of the former contained 145% DNA of the latter. The results obtained suggest that the DNA synthesis in amoeba nuclei may proceed during the whole interphase, and that during the second half of interphase the content of DNA may depend on the feeding intensity in amoebae. After refeeding the starved animals, DNA contents in their nuclei increased to reach the same level as in the constantly fed amoebae seen in the end of interphase.     

云南大叶茶细胞学研究

本文采用去壁低渗法研究了云南大叶茶的染色体核型,间期核形态和多核现象。结果表明大多数染色体是中部着丝粒染色体,5对是近中部着丝粒染色体,第7和12对染色体中各有1条具随体染色体。根据Levan等的分类原则,其核型为2n=20m+8sm+2sm(SAT),属于Stebbins核型分类的“2A”型,同时亦发现有“2B”型的核型。云南大叶茶间期核型为浓密分散型和复杂染色中央微粒型两种;并首次发现茶树中的多核现象,在所观察的1250个细胞中有6个是具双核细胞(占0.48％),有2个是具三核细胞占(0.16％)。另外,本文还对部份山茶属植物的核型进行了讨论。从核型上可以看出:(1)山茶属植物在进化上属于较原始的种系;(2)山茶属植物核型的进化基本符合Stebbins提出的植物界核型进化的规律,即对称—→不对称;(3)山茶属植物的核型在一定范围内变异甚大,这种变异没有一定的规律性。这些观点与张宏达提出的山茶属植物的分类系统基本吻合。带随体的染色体数目在山茶属植物核型的进化上没有什么明显的变化规律。     

大吴风草（菊科：千里光族）的核形态及其系统学意义

研究了大吴风草属的核形态,染色体间期为复杂型;前期 色体为中间型,染色体长度从３．７０μm到２．６４μｍ,平均长度为３．２０μｍ;核型公式为２n=60=14m 26sm 20st(4SAT),为３Ａ类型。过去认为大吴风草属与橐吾属接近,并比之原始,但染色体和花粉特征并不支持这种处理。     

A New Pathogen,Microsporidium itiiti n. sp. (Microsporida), from the Argentine Stem Weevil,Listronotus bonariensis (Coleoptera,Curculionidae)1

A new species of microsporidium (phylum Microspora) infecting the Argentine stem weevil, Listronotus bonariensis (Kuschel. 1955), is described on the basis of light and electron microscope observations. It has the following characteristics: nuclei always isolated; meronts spherical and sporonts ribbon-shaped, with variable numbers of nuclei; sporogony within a vacuole which is bounded by a thin membrane that usually breaks down before uninucleate spores mature; occasionally parts of the membrane remain so that clusters of variable numbers of spores may be seen in light microscopic preparations. Spores measure 2.5 × 1.4 μm (fresh) and development occurs mainly in the midgut, but also in the epidermis, fat body, muscle, and ovaries.     

The centriolar cycle in polykaryons containing prematurely condensed chromosomes or telophase-like nuclei]

In fused interphase-mitotic cells, either interphase nuclei are induced to premature chromosome condensation (PCC) or mitotic chromosomes are induced to telophase-like nuclei (TLN) formation. This study concerns structural and functional changes in centrioles of fused cells in which PCC or TLN are induced. Embryonic pig kidney cells were fused using a modified PEG-DMSO-serum method. Cell cycle period of the nuclei was determined before cell fusion using double-labeling autoradiography. Polykaryons containing desirable type of PCC or interphase nuclear combination in TLN were selected on the basis of isotope labeling after being embedded in epon. Selected cells were cut into serial sections and studied under electron microscope. The data obtained showed that centrioles at every interphase period undergo mitotic activation when their nuclei are induced to PCC. They acquire fibrillar halo and form half-spindles. Daughter centrioles at G1, S and G2 periods are also capable of mitotic activation when separated from their mother centriole. Inert centrioles were found in some cells with G1-PCC. When mitotic nuclei are induced to TLN formation, their centrioles also become inactivated. They lose fibrillar halo and mitotic spindles break down. Some mitotic centrioles develop features characteristic of interphase period such as satellites and vacuoles. Induced nuclear and centriolar changes are simultaneous and may be controlled by the same factor. Mitotic factor of mitotic cell partner which induces PCC may also induce interphase centrioles to mitotic activation. Degradation of the mitotic factor leading to TLN formation may also cause the loss of the mitotic activity of centrioles and disorganization of mitotic spindles.     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Rain and Wind

The influence of wind on the splash dispersal of Septoria nodorum pycnidiospores was studied in a raintower/wind tunnel complex with single drops or simulated rain falling on spore suspensions or infected stubble with windspeeds of 1.5 to 4 m/sec. When single drops fell on spore suspensions (depth 0.5 mm, concentration 7.8 × 10⁵ spores/ml) most of the spore-carrying droplets collected on fixed photographic film between 0–4 m downwind (windspeed 3 m/sec) were >200 μm in diameter. However, most spores were carried in droplets with diameter > 1000 μm, 70 % of which carried more than 100 spores. When simulated rain fell on infected stubble most of the spore-carrying droplets collected beyond 1 m downwind (windspeeds 1.4 and 4 m/sec) were <200 μm in diameter and none were >600 μm; most of these droplets carried only one spore. The distribution of splash droplets (with diameter >100 μm) deposited on chromatography paper showed a maximum at 40–50 cm upwind of the target but many more droplets were deposited 20–30 cm downwind, when single drops fell on a spore suspension (concentration 1.2 × 10⁵ spores/ ml) containing fluorescein dye with a windspeed of 2 m/sec; droplets were collected up to 3 m downwind but not more than 70 cm upwind. With a windspeed of 3 m/sec, numbers of sporecarrying droplets and spores collected on film decreased with increasing distance downwind; most were collected within 2 m of the target but some were found up to 4 m. When simulated rain fell on infected stubble, increasing the windspeed from 1.5 to 4 m/sec greatly increased the number of spores deposited more than 1 m downwind. At 1.5 m/sec none were collected beyond 2 m downwind, whereas at 4 m/sec some were collected at 4 m. A few air-borne S. nodorum spores were collected by suction samplers at a height of 40 cm at distances up to 10 m downwind of a target spore suspension on which simulated rain fell.     

Reversible chromosome condensation induced in Drosophila embryos by anoxia: visualization of interphase nuclear organization

We have studied the morphology of nuclei in Drosophila embryos during the syncytial blastoderm stages. Nuclei in living embryos were viewed with differential interference-contrast optics; in addition, both isolated nuclei and fixed preparations of whole embryos were examined after staining with a DNA-specific fluorescent dye. We find that: (a) The nuclear volumes increase dramatically during interphase and then decrease during prophase of each nuclear cycle, with the magnitude of the nuclear volume increase being greatest for those cycles with the shortest interphase. (b) Oxygen deprivation of embryos produces a rapid developmental arrest that is reversible upon reaeration. During this arrest, interphase chromosomes condense against the nuclear envelope and the nuclear volumes increase dramatically. In these nuclei, individual chromosomes are clearly visible, and each condensed chromosome can be seen to adhere along its entire length to the inner surface of the swollen nuclear envelope, leaving the lumen of the nucleus devoid of DNA. (c) In each interphase nucleus the chromosomes are oriented in the "telophase configuration," with all centromeres and all telomeres at opposite poles of the nucleus; all nuclei at the embryo periphery (with the exception of the pole cell nuclei) are oriented with their centromeric poles pointing to the embryo exterior.     

Interphase fluorescence in situ hybridization mapping: a physical mapping strategy for plant species with large complex genomes

The chromatin in interphase nuclei is much less condensed than are metaphase chromosomes, making the resolving power of fluorescence in situ hybridization (FISH) two orders of magnitude higher in interphase nuclei than on metaphase chromosomes. In mammalian species it has been demonstrated that within a certain range the interphase distance between two FISH sites can be used to estimate the linear DNA distance between the two probes. The intephase mapping strategy has never been applied in plant species, mainly because of the low sensitivity of the FISH technique on plant chromosomes. Using a CCD (charge-coupled device) camera system, we demonstrate that DNA probes in the 4 to 8 kb range can be detected on both metaphase and interphase chromosomes in maize. DNA probes pA1-Lc and pSh2.5·SstISalI, which contain the maize locia1 andsh2, respectively, and are separated by 140 kb, completely overlapped on metaphase chromosomes. However, when the two probes were mapped in interphase nuclei, the FISH signals were well separated from each other in 86% of the FISH sites analyzed. The average interphase distance between the two probes was 0.50 µm. This result suggests that the resolving power of interphase FISH mapping in plant species can be as little as 100 kb. We also mapped the interphase locations of another pair of probes, ksu3/4 and ksu16, which span theRp1 complex controlling rust resistance of maize. Probes ksu3/4 and ksu16 were mapped genetically approximately 4 cM apart and their FISH signals were also overlapped on metaphase chromosomes. These two probes were separated by an average of 2.32 µm in interphase nuclei. The possibility of estimating the linear DNA distance between ksu3/4 and ksu16 is discussed.     

Cytological and molecular description of Hamiltosporidium tvaerminnensis gen. et sp. nov., a microsporidian parasite of Daphnia magna, and establishment of Hamiltosporidium magnivora comb. nov

We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha- and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jírovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4·9-5·6×2·2-2·3 μm) and have their polar filament arranged in 12-13 coils. A second, elongated spore type (6·8-12·0×1·6-2·1 μm) is rod-shaped with blunt ends and measures 6·8-12·0×1·6-2·1 μm. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. nov.     

Intranuclear fibrillar material in cereal pollen mother cells

Ultrastructural studies of cereal anthers found intranuclear bundles of microfilaments in pollen mother cells (PMCs) but not elsewhere. The ultrastructure, distribution, and behaviour of this fibrillar material (FM) are described. FM was seen in all 19 genotypes studied comprising Aegilops, Triticum, Secale, Hordeum and Avena species, which together included haploid, diploid and allo-and autopolyploid, and natural and synthetic polyploid examples. Detailed studies in diploid S. cereale, and hexaploid T. aestivum and Triticale showed that FM was present in PMC nuclei during premeiotic interphase, leptotene and zygotene but not at pachytene and later meiotic stages. Moreover, it was most abundant at late premeiotic interphase in T. aestivum, and at leptotene in S. cereale and Triticale, when it occurred in up to 100% of sampled PMC nuclei in an anther. Although FM and synaptonemal complex (SC) occurred together in some PMC nuclei at later stages, FM was present long before SC, and reached its peak of abundance before SC did. Bundles of FM often formed links at their ends between either two masses of chromatin, or more rarely, between chromatin and the nuclear membrane. Individual bundles of FM varied in length but showed roughly similar ranges of lengths and widths in these three species. They were up to about 0.2 m in diameter and about 3 m in length, equivalent to about 20% of the maximum diameter of the nuclei containing them. Reconstructions of PMC nuclei indicated that FM was never associated with centromeres but was sometimes, and perhaps usually, associated with telomeric or sub-telomeric chromosome segments.The function of FM is unknown but its possible role is discussed in relation to (1) previously described intranuclear inclusions in meiocytes and (2) the cytogenetics and developmental behaviour of meiotic nuclei in the wheat comparium. As FM was a constant and characteristic structural component of PMC nuclei, its presence is probably of functional significance to the meiotic process. If so, it may function before, and over greater distances, than SC in establishing or maintaining the coorientation of chromosomes prerequisite for normal chromosome pairing. As FM was most abundant at stages when major chromosome movements occur, yet its distribution was non-centromeric, it is suggested that it may function in the attachment and movement of telomeres at the nuclear membrane formed after premeiotic mitosis. The possibility that a bundle of FM normally links corresponding sites on two homologues is considered.     

Nuclear Staining of Colletotrichum Gloeosporioides F. SP. Malvae Conidia with Fluorescent and Nonfluorescent Stains

Six different staining techniques were evaluated for their suitability to stain nuclei of Colletotrichum gloeosporioides f. sp. malvae (C.g.m.) spores. Of the three fluorescent stains, DAPI (4',6-diamidino-2-phenylindole) and bisbenzimide (Hoechst 33258) stained spore nuclei well; mithramycin did not. To achieve consistent results with the bisbenzimide staining protocol, the spores had to be fixed prior to staining and the stain had to be supplemented with Triton X-100. Both safranin O and Giemsa were suitable nonfluorescent staining techniques; lomofungin was not. Safranin O staining was simple and rapid. However, reproducibility was better if the spore suspension and KOH droplets were rapidly mixed prior to adding the stain. There was no significant difference in the percentages of uninucleate and binucleate spores observed in spore preparations stained with DAPI, bisbenzimide, safranin O or Giemsa. Bisbenzimide and safranin O were found to be simple, rapid and reliable fluorescent and nonfluorescent techniques, respectively, for staining nuclei of C.g.m. spores.     

Description of Hyalinocysta expilatoria n. sp., a microsporidian parasite of the blackfly Odagmia ornata

Hyalinocysta expilatoria n. sp. is described from a larva of Odagmia ornata collected in Sweden. Infection was restricted to the adipose tissue which was transformed into a syncytium. The earliest stage observed was diplokaryotic merozoites, which mature directly into diplokaryotic sporonts. Each sporont produces a sporophorous vesicle (pansporoblast), which persists, also enclosing mature spores. Usually nuclear divisions result in a plasmodium with 8 nuclei, which fragments into 8 sporoblasts, each of which develops into a spore without further division. Occasionally an aberrant number of spores (2, 4, 6) is formed. The spores are pyriform with a flattened area at the posterior pole. Spores in sporophorous vesicles with 8 spores are 4.0–6.0 μm long, in vesicles with 4 spores 4.0–5.0 μm, and in vesicles with 2 spores 7.0–8.0 μm. In some vesicles the spores develop asynchronously, and 2, 4, or 6 mature spores are found together with 6, 4, or 2 immature. There was also a small number of vesicles with supernumerary spores, less than 8 normally developed. The 325–350 nm thick spore wall is composed of three layers. The polar filament is anisofilar with 7 coils in a single layer. The anterior 5–6 coils are wide, the posterior 2-1 thin. The angle of tilt of the anterior filament coil is approximately 50°. The spore has a single nucleus. The sporophorous vesicle is delimited by a thin membrane, also visible in haematoxylin stained preparations. Vesicles with mature spores are void of metabolic inclusions.     

Fluorescent staining of L cell centromeres and chromocenters with 1-dimethylaminonaphthalene-5-sulfonyl chloride and G-bandings

Fluorescent staining patterns of L cell chromosomes with 1-dimethylaminonaphthalene-5-sulfonyl chloride (dansyl chloride) were studied. Ordinary air-dried L cell metaphase chromosomes exhibited relatively uniform and bright yellowish green fluorescence by dansyl-staining under the fluorescence microscope. However, after the chromosome preparations were treated with 10 mM NaCl for 24 h at 4 °C, which produced distinctive G-bands with Giemsa-staining, the centromeric regions and several interstitial regions of some particular chromosomes were clearly fluorescent but other regions showed only dull fluorescence. After the treatment of chromosome slides with cupric sulfite reagent, which converts sulfhydryls and disulfides to thiosulfates chromosomes showed clear G-bands which were indistinguishable from those after 10 mM NaCl treatment. By dansyl-staining, however, the cupric sulfite-treated chromosomes exhibited very faint fluorescence on their contour alone, and neither centromeric regions nor some interstitial regions of marker chromosomes had distinctly bright fluorescence.Although Giemsa-staining disclosed dark chromocenters in approx. 75% of interphase nuclei irrespective of pretreatments, dansyl-staining revealed bright chromocenters in approx. 60% of interphase nuclei in control slides, in about 40% of nuclei in 10 mM NaCl-treated slides, and in only about 30% of nuclei in cupric sulfite-treated preparations.These observations indicated that in the air-dried chromosome preparations, the distribution of protein over the metaphase chromosome is relatively uniform along its length, and that G-bands in the chromosome and Giemsa-staining of chromocenters in interphase nuclei are not significantly affected by apparent loss of protein from the preparations. It was also suggested that particular protein may be associated with the centromeric regions of L cell chromosomes. Some technical details of dansyl fluorochroming and the significance of the observations were discussed.     

SPORE ULTRASTRUCTURE OF THE MYXOMYCETE PHYSARUM POLYCEPHALUM

Spores of the true slime mold Physarum polycephalum were examined at several stages of their development by means of scanning and transmission electron microscopy. The spores were globose, spine-covered structures produced within a sporangium enclosed in a tough, noncellular peridium. Cytologically, the spore represented a typical eukaryotic cell, having discrete organelles similar to spores of other myxomycetes. The presence of dictyosomes, helical filaments, and microbodies in these cells, as well as the further elucidation of the cell wall and the “polysaccharide-containing” areas, represent new contributions to the ultrastructure of the myxomycete spore. Of special interest were observations of metaphase nuclei just prior to spore cleavage, interphase nuclei in young spores, and nuclei in mature spores containing synaptonemal complexes. These observations indicate that in Physarum polycephalum mitosis occurs just prior to spore cleavage, and meiosis takes place after spore cleavage.     

Structure of chromatin and chromosomes in preparations of interphase nucleus derivatives, prepared by removal of the nucleuar envelopes. II. Structure of chromatin and associations of chromosomes in stretched amembranous nuclei and mitotic figures]

Preparations of surface stretched amembranous nuclei and mitotic figures were used for revealing the high order nuclear and chromosomal structures. The preparations were obtained by dropping amembraneous nuclei and mitotic figures suspension in methanol-glacial acetic acid mixture (3:1) on wetted superclean slides. Amembraneous nuclei and mitotic figures were isolated from intact murine and human cells (lines L1210, SK-UT-1B, PHA-stimulated lymphocytes) by means of their 1-5 min prefixational capillary pipetting with freshly prepared 0.018-0.06% Triton X-100 solution in the conditional cultural medium. Stretched amembraneous nuclei and mitotic figures had no features of induced chromatin dispersion and compaction. Stretched interphase amembraneous nuclei showed spatially separated individual structures (thin chromatin fibres, nucleoli, intranuclear bodies), polymorphous pattern of perinucleolar chromatin aggregation and episodically expressed beaded thick chromatin fibres and a chromocenter. The chromomeric pattern of the spread chromosomes of mitotic figures was quite similar but hardly identical with that of G-banding. The stretched prometaphase mitotic figures in all tested cell types always contained loose "residual" nucleoli looking like typical prophase nucleoli as concerns their shape and number per cell (mitotic figure). The majority of chromosomes of stretched mitotic figures and of prophase amembraneous nuclei were attached to the nucleolar material. All tested cell lines showed almost the same variation in number of nucleolus-attached chromosomes, per both prophase amembraneous nucleus and prometaphase mitotic figure. Some chromosomes of stretched mitotic figures were colocated with "residual" nucleoli and looked shortened and strongly condensed. Other chromosomes, locally associated with "residual" nucleoli, were straight and oriented radially to these. Mutual chromosomal arrangements in mitotic cells on smears and in stretched mitotic figures were analogous. Equatorial plates from PBS-washed SK-UT-1B cells displayed a better stretching capacity than those from untreated cells. In the former case metaphase chromosomes were seen more uniformly stretched and well identified after GTG-banding procedure. The number of interchromosomal (mainly telomere-telomeric and telomere-centromeric) connections per stretched mitotic figure (or per stretched prophase amembraneous nucleus) was minimum in late prometaphase, maximum in prophase and early prometaphase, and intermediate in metaphase. The obtained data are discussed in terms of topology and longitudinal heterogeneity of mitotic chromosomes.     

Genetic Control of Mitosis: Mutation ff3Causes Premature Beginning of Telophase Chromatin Reorganization in Drosophila melanogaster

The effect of cell cycle mutation ff3 on chromosome segregation was studied on fixed cells of neural ganglia of Drosophila melanogasterlarvae. The cell distributions by diameter of interphase nuclei and by distance between sister chromatid sets were compared at anaphase and telophase. In the control wild-type strain Lausenne, the cell distribution by distance between sister chromatids in anaphase was similar to their distribution by nuclear size. The mean distance between segregating chromatids at anaphase (l _av) coincided with the mean diameter of interphase nuclei (d _av) and was 8.3 m. Cells passed to telophase when chromatids were at least 10 m apart. The mutant ff3 strain differed from the control strain Lausenne in cell distribution by interphase nuclear diameter and distance between sister chromatids in anaphase; the mean nuclear diameter and mean distance between segregating chromatids similarly increased to 9.3 m. A specific feature of mitosis in mutant strain ff3 was a premature beginning of telophase chromatin reorganization. This caused the occurrence of cells with abnormally short (less then the interphase nuclear diameter) distance between sister chromatid sets in telophase but not in anaphase, as if these cells had passed from anaphase to telophase prematurely, during the chromatid movement toward poles in anaphase A.     

Dispersal of Rhynchosporium secalis conidia from infected barley leaves or straw by simulated rain

Simulated rain (mean drop diameter c. 1 or 3 mm) was allowed to fall for 10 – 15 min on to barley leaves or straw infected by Rhynchosporium secalis (leaf blotch). The leaves were supported on a mesh through which run-off water drained and the straw was supported on a rigid surface on which run-off water collected. The numbers of R. secalis conidia and spore-carrying splash droplets collected by horizontal samplers (microscope slides and pieces of photographic film) decreased rapidly with increasing distance from and increasing height above the sources, with half-distances of 2 – 10 cm. Less than 10% of the spores or droplets reached heights of more than 30 cm. Incident drops 3 mm in diameter produced more spore-carrying droplets and dispersed more conidia than did 1 mm drops. The size category of splash droplets with the greatest proportion of the spore-carrying droplets dispersed by 3 mm drops was 200 – 400 μm, whether the source was infected barley leaves or barley straw. For leaves or straw the greatest proportions of spores were carried in droplets > 1000 μm in diameter. The mean diameter of spore-carrying droplets (478 μm) dispersed from free-draining leaves was less than that of droplets from straw plus run-off water (563 μm). However, the leaf source had more spores cm^-2 and the mean number of spores per droplet was greater (113 as opposed to 6·8) than for the straw source.