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Like other cells, fungal hyphae show exquisite sensitivity to their environment. This reactiveness is demonstrated at many levels, from changes in the form of the hypha resulting from alterations in patterns of exocytosis, to membrane excitation, and mechanisms of wound repair. Growing hyphae detect ridges on surfaces and respond to restrictions in their physical space. These are expressions of cellular consciousness. Fungal mycelia show decision-making and alter their developmental patterns in response to interactions with other organisms. Mycelia may even be capable of spatial recognition and learning coupled with a facility for short-term memory. Now is a fruitful time to recognize the study of fungal ethology as a distinctive discipline within mycology.

Despite the longstanding use of dried mushrooms and mushroom extracts in traditional Chinese medicine, there is no scientific evidence to support the effectiveness of these preparations in the treatment of human disease. Consumers should evaluate assertions made by companies about the miraculous properties of medicinal mushrooms very critically. The potential harm caused by these natural products is another important consideration. In a more positive vein, the presence of potent toxins and neurotropic compounds in basidiomycete fruit bodies suggests that secondary metabolites with useful pharmacological properties are widespread in these fungi. Major investment in controlled experiments and objective clinical trials is necessary to develop this natural pharmacopeia.

This study concerns the thermotolerance of spores of mesophilic fungi isolated from a tropical semi-arid habitat subject to dry season fire in the Western Ghats, southern India. Among 25 species of Ascomycota isolated from leaf litter, nine were able to grow after incubation in a drying oven for 2h at 100°C; the spores of two of these species survived 2h incubation at 110°C, and one survived exposure to 115°C for 2h. The range of thermotolerance among mesophilic fungi isolated from the leaf litter was surprising: filamentous fungi from other habitats, including species that colonize scorched vegetation after fires and thermophilic forms occurring in self-heating plant composts, cannot survive even brief exposure to such high temperatures. It is possible that the exceptional heat resistance of the Indian fungi is related to adaptations to surviving fires. Genetic analysis of the physiological mechanisms of heat resistance in these fungi offers prospects for future biotechnological innovations. The discovery of extreme thermotolerance among common saprotrophs shows that this physiological trait may be more widespread than recognized previously, adding to concern about the evolution of opportunistic pathogens on a warmer planet. The fungi in this study are among the most heat-resistant eukaryotes on record and are referred to here as 'Agni's Fungi', after the Hindu God of Fire.

Active discharge of basidiospores in most species of Basidiomycota is powered by the rapid movement of a droplet of fluid, called Buller’s drop, over the spore surface. This paper is concerned with the operation of the launch mechanism in species with the largest and smallest ballistospores. Aleurodiscus gigasporus (Russulales) produces the largest basidiospores on record. The maximum dimensions of the spores, 34 × 28 µm, correspond to a volume of 14 pL and to an estimated mass of 17 ng. The smallest recorded basidiospores are produced by Hyphodontia latitans (Hymenochaetales). Minimum spore dimensions in this species, 3.5 × 0.5 µm, correspond to a volume of 0.5 fL and mass of 0.6 pg. Neither species has been studied using high-speed video microscopy, but this technique was used to examine ballistospore discharge in species with spores of similar sizes (slightly smaller than A. gigasporus and slightly larger than those of H. latitans). Extrapolation of velocity measurements from these fungi provided estimates of discharge distances ranging from a maximum of almost 2 mm in A. gigasporus to a minimum of 4 µm in H. latitans. These are, respectively, the longest and shortest predicted discharge distances for ballistospores. Limitations to the distances traveled by basidiospores are discussed in relation to the mechanics of the discharge process and the types of fruit-bodies from which the spores are released.

Rhizomorphs of wood-decay basidiomycetes are root-like structures produced by the coordinated growth of thousands of hyphae. Very little is known about their development nor the way that they penetrate soils and rotting wood. In this study, we applied techniques used in previous studies on hyphae to explore the mechanics of the invasive growth process in Armillaria gallica. Growth rate measurements were made in media with different gel strengths. The osmolyte composition of rhizomorph sap was determined spectroscopically and the forces exerted by growing tips were measured using a force transducer. Cultured rhizomorphs extended at much faster rates than unbundled hyphae (3.5 mm d−1 versus 1.5 mm d−1) and their growth accelerated in response to increased medium gel strength (to 7.4 mm d−1). Measurements of rhizomorph osmolality provided a turgor pressure estimate of 760 kPa (7.5 atm.), and spectroscopic analysis showed that this pressure was generated by the accumulation of erythritol, mannitol, and KCl. Forces exerted by growing tips ranged from 1 to 6 mN, corresponding to pressures of 40–300 kPa (0.4–3.0 atm.). Pressures exerted by extending rhizomorphs are comparable to those produced by individual vegetative hyphae. This suggests that the mechanical behavior of hyphae is similar whether they grow as unbundled cells or aggregate to form macroscopic rhizomorphs.

Conidial dispersal in Stachybotrys chartarum in response to low-velocity airflow was studied using a microflow apparatus. The maximum rate of spore release occurred during the first 5 min of airflow, followed by a dramatic reduction in dispersal that left more than 99% of the conidia attached to their conidiophores. Micromanipulation of undisturbed colonies showed that micronewton (microN) forces were needed to dislodge spore clusters from their supporting conidiophores. Calculations show that airspeeds that normally prevail in the indoor environment disturb colonies with forces that are 1000-fold lower, in the nanonewton (nN) range. Low-velocity airflow does not, therefore, cause sufficient disturbance to disperse a large proportion of the conidia of S. chartarum.

Stipe elongation in fruit bodies of Coprinopsis cinerea (syn. Coprinus cinereus) was examined from a biomechanical perspective. Two strains were studied: the self-compatible Amut Bmut homokaryon that produces normal fruit bodies with relatively short stipes, and mutant B1918 that produces abnormally elongated stipes. Measurements of the pressure exerted by developing mushrooms were made using strain gauges, and these data were compared with measurements of the pressures exerted by vegetative hyphae of the same strains. The experiments demonstrate that AmutBmut hyphae elongating within stipe tissue push with the same pressure (approx. 0.5 atmosphere) as vegetative hyphae growing through their food sources. In purely biomechanical terms, the fruit body may therefore be viewed as a relatively uncomplicated sum of its parts. Analysis of the mutant strain B1918 demonstrated that hyperelongation of the stipe is not associated with any difference in the pressure exerted by the fruit body. The fault in the mechanism of stipe extension in B1918 may be reflected in the increased fluidity of the cell wall of vegetative hyphae of this strain, but further work is necessary to resolve this.

Analysis of airflow patterns around models of mushrooms and fresh fruiting bodies in a low speed wind tunnel showed division of the airstream at the leading edge of the cap, an increase in wind speed a few millimeters above and below the cap, and the development of a mantle of very slow-moving air closer to the lower surface. Mushroom caps with a pronounced bell shape offered the greatest interrup- tion to airflow and showed the maximum reduction in wind speed beneath their lower surface. Calcula- tions suggest that the measured decrease in wind speed may reduce the number of spores that are blown back into the cap, promoting dispersal from the fruiting body.

Melanins are complex black polymers of resonance stabilized cyclic subunits (including in- doles, phenols, hydroxynaphthalenes) and are noto- riously intractable to chemical analysis. Cell walls of numerous fungi are melanized, rendering many spores, vegetative hyphae, and certain fruit bodies opaque. Melanin deposition protects the pigmented cell from physical and biological stresses, excludes poisons, and helps limit leakage of certain metabo- lites. By forming a physical barrier between the cell and its surroundings, the production of a melanized wall layer has a profound effect upon the interactions between pathogenic fungi and their hosts. In many plant and animal diseases caused by melanotic fungi, melanin biosynthesis is an important determinant of pathogenicity and virulence. The mode of action of melanin in these diseases is the subject of intensive research, and a variety of mechanisms that link fun- gal melanin and disease have been discovered.

Filamentous fungi and yeasts control cytoplasmic osmotic pressure through ion accumulation and synthesis of compatible osmolytes including polyhydric alcohols (polyols), proline, and trehalose. Authoritative data on the osmotic effects of these compounds were obtained using vapour pressure deficit osmometry. All osmolytes tested were characterised by nonlinear relationships between concentration and osmotic pressure. At high concentrations larger polyols generated higher osmotic pressures than smaller ones, though differences between the osmotic effects of polyols with three, four, five and six carbon atoms were not pronounced at lower (physiological) concentrations. Proline shared a similar relationship between concentration and osmotic pressure with polyols with five carbon atoms, while at concentrations above 0.5 M trehalose generated higher osmotic pressures than any of the polyols tested. Mixtures of trehalose and glycerol boosted osmotic pressure in a synergistic rather than additive fashion. These data provide new clues to the adaptive significance of glycerol accumulation, and also suggest that complex patterns of osmolyte synthesis are not due to differences between the osmotic effects of these compounds.

Stab inoculation of agar medium with yeasts of the human pathogen Wangiella dermatitidis resulted in induction of invasive hyphae. Mechanical penetration of agar was indicated by the observation that an increase in medium gel strength slowed the rate of substrate invasion. A melanized wild-type strain (8656) exhibited much faster invasive growth through 2–8% agar than three melanin-deficient mutants. Inhibition of melanin synthesis in strain 8656 using tricyclazole resulted in a decrease in its rate of invasive growth, while scytalone restored melanin synthesis in the albino mel3 strain and boosted its rate of invasive growth. Earlier research established that cellular melanization is also associated with invasive hyphal growth in the mouse brain, and infections with strain 8656 are invariably lethal. Together, these in vitro and in vivo data indicate that biomechanical characteristics of fungi may be important determinants of virulence and disease progression in human and animal mycoses.

Classical studies on spore release within the Saprolegniaceae (Oomycetes) led to the proposition that different mechanisms of sporangial emptying represent steps in an evolutionary transition series. We have reevaluated this idea in a phylogenetic framework using internal transcribed spacer sequences of four genera. These data were compared with the response to osmotic stress exhibited by each taxon. Saprolegnia emerges as the most basal genus, sister to Achlya, Thraustotheca, and Dictyuchus. Achlya and Thraustotheca are most closely related, while Dictyuchus appears to have evolved along a separate evolutionary lineage. The resulting phylogenetic framework is consistent with the idea that the mechanism of sporangial emptying exhibited by Saprolegnia represents the plesiomorphic condition from which the other mechanisms were derived independently. These alternative mechanisms of spore release may have resulted from a small number of mutations that inhibited axonemal development and altered the temporal and spatial expression of lytic enzymes that degrade the sporangial wall. Copyright 1998 Academic Press.

Money, N. P., and Howard, R. J. 1996. Confirmation of a link between fungal pigmentation, turgor pressure, and pathogenicity using a new method of turgor measurement.Fungal Genetics and Biology20,217–227. A novel approach to turgor measurement has confirmed a link between melanin synthesis and appressorial turgor pressure in the rice blast fungusMagnaporthe grisea.The new technique employs a cold stage to measure the melting point of ice within individual cells. Turgor is then calculated from the difference between the melting points of intracellular ice and ice in the fluid surrounding the cell. Conidia ofM. griseawere incubated on various surfaces, and appressoria developed within 6 h. Measurements from conidia showed that wild-type and melanin-deficient strains generated the same pressures, which decreased before germ tube emergence. By contrast, wild-type appressoria generated much higher pressures than appressoria of a melanin-deficient buf−mutant. These experiments strengthen the hypothesis that melanin confers pathogenicity by facilitating the development of high pressures within appressoria.

Viscous drag causes the rapid deceleration of fungal spores after high-speed launches and limits discharge distance. Stokes' law posits a linear relationship between drag force and velocity. It provides an excellent fit to experimental measurements of the terminal velocity of free-falling spores and other instances of low Reynolds number motion (Re10 m/s and travel as far as 2.5 m (Re>100).

Gilled mushrooms are produced by multiple orders within the Agaricomycetes. Some species form a single array of unbranched radial gills beneath their caps, many others produce multiple files of lamellulae between the primary gills, and branched gills are also common. In this largely theoretical study we modeled the effects of different gill arrangements on the total surface area for spore production. Relative to spore production over a flat surface, gills achieve a maximum 20-fold increase in surface area. The branching of gills produces the same increase in surface area as the formation of free-standing lamellulae (short gills). The addition of lamellulae between every second gill would offer a slightly greater increase in surface area in comparison to the addition of lamellulae between every pair of opposing gills, but this morphology does not appear in nature. Analysis of photographs of mushrooms demonstrates an excellent match between natural gill arrangements and configurations predicted by our model.

Ballistospore discharge is a feature of 30 000 species of mushrooms, basidiomycete yeasts and pathogenic rusts and smuts. The biomechanics of discharge may involve an abrupt change in the center of mass associated with the coalescence of Buller's drop and the spore. However this process occurs so rapidly that the launch of the ballistospore has never been visualized. Here we report ultra high- speed video recordings of the earliest events of spore dispersal using the yeast Itersonilia perplexans and the distantly related jelly fungus Auricularia auricula. Im- ages taken at camera speeds of up to 100 000 frames/ s demonstrate that ballistospore discharge does in- volve the coalescence of Buller's drop and the spore. Recordings of I. perplexans demonstrate that al- though coalescence may result from the directed col- lapse of Buller's drop onto the spore, it also may in- volve the movement of the spore toward the drop. The release of surface tension at coalescence pro- vides the energy and directional momentum to pro- pel the drop and spore away from the fungus. Anal- yses show that ballistospores launch into the air at initial accelerations in excess of 10 000 g. There is no known analog of this micromechanical process in an- imals, plants or bacteria, but the recent development of a surface tension motor may mimic the fungal bi- ology described here.

The in vitro physiological characteristics of three species of Pythium (oomycetes) that utilize different food sources were compared with their ecological activities: P. insidiosum is a pathogen of mammals (including humans), P. graminicola infects the roots of graminaceous hosts, and P. grandisporangium is an enigmatic water mold isolated from mangrove leaves and marine algae. P. insidiosum and P. graminicola showed peak growth rates at 37 °C before complete inhibition of growth at 40 °C; P. grandisporangium grew fastest at 22 °C. Differences between the invasive pressures exerted by the hyphae of these microorganisms were not considered significant in relation to the substrates colonized by these water molds. All three species showed substantial secreted protease activity, producing three or more serine proteases with weights ranging from 24-38 kDa. Fastest growth rates were supported when collagen was supplied as the sole carbon source, and none of the species were able to grow on purified plant cell wall polysaccharides. The growth and nutritional characteristics of P. graminicola and P. grandisporangium bear little obvious relationship to the ecological niches that they inhabit. This highlights the caution necessary in extrapolating from laboratory analyses to the natural environment, and points to the potential importance of ecological opportunity in determining the host range and food source of certain microorganisms.

Diverse microorganisms traditionally called fungi are recognized as members of two kingdoms: mushroom-forming species and their relatives in the Fungi, and oomycete water molds in the Stramenopila. Phylogenetic analysis suggests that these kingdoms diverged early in the evolution of eukaryotes. The phylogenetic detachment of the fungi and oomycetes is reflected in radical differences in their biochemistry, cell structure, and development. In terms of their biological activities, however, they show great similarity, because both groups form colonies of filamentous hyphae that invade and decompose solid food sources. Here we present biomechanical evidence of the convergent evolution of the invasive growth process in these microorganisms. Using miniature strain gauges to measure the forces exerted by single hyphae, we show that the hyphae of species in both kingdoms exert up to 2 atmospheres of hydrostatic pressure as they extend at their tips. No other eukaryotes have adopted this process for meeting their nutritional needs.

Forces exerted by hyphae of the phytopathogen Pythium graminicola and mammalian pathogen Pythium insidiosum were compared with the mechanical resistance of their hosts’ tissues. Hyphal apices of both species exerted a mean force of 2 μN , corresponding to mean pressures of 0.19 μN μm −2 (or MPa) for P. graminicola, and 0.14 μN μm −2 for P. insidiosum. Experiments with glass microprobes showed that the epidermis of grass roots resisted penetration until the pressure applied at the probe tip reached 1–12 μN μm −2 . Previously published data show that mammalian skin offers even greater resistance ( 10–47 μN μm −2 ). Clearly, tissue strength exceeds the pressures exerted by hyphae of these pathogens, verifying that secreted enzymes must play a critical role in reducing the resistance of plant and animal tissues. It is presumed that hyphae are sufficiently powerful to bore through any obstacles remaining after enzyme action.

The relative significance of mechanical penetration versus the action of substrate-degrading enzymes during solid tissue invasion has not been established for any fungal disease. Pythium insidiosum is an oomycete fungus (or stramenopile) that causes a rare, but potentially lethal infection in humans and other mammalian hosts. Experiments with miniature strain gauges showed that single hyphal apices of this pathogen exert forces of up to 6.9 microN, corresponding to maximum pressures of 0.3 microN microm(-2) or MPa. Samples of cutaneous and subcutaneous tissue from fresh human cadavers displayed a mean strength (resistance to needle puncture) of 24 microN microm(-2), and a mean pressure of 30 microN microm(-2) was necessary to penetrate skin strips from slaughtered horses. These experiments demonstrate that P. insidiosum does not exert sufficient pressure to penetrate undamaged skin by mechanics alone, but must effect a decisive reduction in tissue strength by proteinase secretion.

Mycelia of Gaeumannomyces graminis var. graminis form large cells called hyphopodia with deeply lobed, melanized walls. Like appressoria produced by other pathogens, hyphopodia develop on hydrophobic surfaces, but it is not clear that hyphopodia function as platforms for host penetration. In appressoria, melanin synthesis is linked to the generation of enormous turgor pressures that provide the necessary force for plant penetration. In the present study, hyphopodial turgor was measured in a wild-type strain of G. graminis var. graminis, a mutant exhibiting constitutive synthesis of melanin (referred to as the dark mutant), and a melanin-deficient strain (thr). These experiments demonstrate that hyphopodia of the wild-type strain generate higher pressures than the dark mutant and that nonmelanized thr hyphopodia generate minuscule internal pressures. Melanization of the wall is also associated with an increase in its rigidity. These data correlate with differences in wall permeability consistent with a recent model for turgor generation by appressoria.

The water molds Achlya bisexualis Coker and Saprolegnia ferax (Gruithuisen) Thuret (Class: Oomycetes) normally grow in the form of slender hyphae with up to 0.8 MPa (8 bar) of internal pressure. Models of plant cell growth indicate that this turgor pressure drives the expansion of the cell wall. However, under conditions of prolonged osmotic stress, these species were able to grow in the absence of measurable turgor. Unpressurized cells of A. bisexualis grew in the form of a plasmodium-like colony on solid media, and produced a multinucleate yeast-like phase in liquid. By contrast, the morphology of S. ferax was unaffected by the loss of turgor, and the mold continued to generate tip-growing hyphae. Measurements of cell wall strength indicate that these microorganisms produce a very fluid wall in the region of surface growth, circumventing the usual requirement for turgor.

As one of the endangered breed of mycologists to have maintained an interest in oomycetes, I am compelled to defend the rationale in continuing to refer to these micro-organisms as fungi. This paper is stimulated by recent communications in which my mycological colleagues have, with apparent relish, pointed to what they perceive as inaccurate references to oomycetes as fungi. David Moore (1997) provides a prime example in his review of The Growing Fungus edited by N. A. R. Gow & G. M. Gadd (1995). Moore criticizes the editors for allowing so many pages of their book to be devoted to these micro-organisms, when ‘…Neurospora is probably more closely related to a cow's nose than it is to Saprolegnia’. While a phylogenetic chasm separates the oomycetes from other fungi, I shall argue that it is impractical to restrict the usage of the term fungus to those micro-organisms that qualify as members of the Phylum Fungi (Alexopoulos, Mims & Blackwell, 1996, provide a contemporary overview of fungal systematics). This argument should have been settled by a series of clear-sighted articles published after molecular genetic analyses confirmed the polyphyletic nature of the fungi (Christensen, 1990; Bruns, White & Taylor, 1991; Hawksworth, 1991; Barr, 1992). For example, Donald Barr (1992) suggested that oomycetes are fungi in the colloquial sense of the term and that it is the colloquial sense of the term that will continue to be most meaningful to mycologists. But since the message of these articles was apparently missed by many mycologists, I hope that this note will clarify a practical definition of the fungi that includes the oomycetes but which does not conflict with a natural classification of the Phylum Fungi that excludes them.

This issue of Mycological Research News features: Fungal irritability and survival mechanisms; In this issue; Genetic markers in single spores of AM fungi; Rice blast fungus attacks leaves and roots differently; Why picking wild mushrooms might be bad behaviour; and life-style choices in lichen-farming and lichen-dwelling fungi. Physiological and ecological papers in this part investigate peroxide accumulation and cell death, stress responses to peroxide and paraquat, and fungal decomposition of leaves in streams. Molecular studies address: phylogenetic relationships of Lecanoromycetes ; correlations with toxin production in Fusarium species; detection techniques for ectomycorrhizal fungi; the status of Xanthoria aureola ; the identity of a sterile red endophyte of cereals; Lepista in Australia; native Alternaria brassicicola populations; and the placement of southern African truffles. The following new scientific names are introduced: Eremiomyces and Kalaharituber gens. nov.; E. echinulatus (syn. Choirmyces echinulatus ) and K. pfeilii (syn. Tuber pfeilii ) combs. nov.

This month Mycological Research News features group sex in New England, the recovery of viable fungal spores from 140 000 year old glaciers, and the role of ericoid mycorrhizas in conveying arsenate resistance to their plant partners. The lead paper in this issue is an historical and morphological critique of the supposed differences of gasteromycetes from other basidiomycetes. Amongst the other 17 papers in this issue are molecular studies on Ganoderma in Australia, Melampsora on Salix, Phaeosphaeria sexual progeny, endomycorrhizal Pisolithus isolates, and cultured and in situ wood decomposing fungi. Complementary isozyme studies on Ganoderma in Australia are also presented. Adhesion and infection in Pestalotiopsis conidia has been examined, the yeasts associated with ant mounds in Texas analyzed, dual infections of grasses with different Neotyphodium endophytes studied experimentally, the detection of Botrytis cinerea by monoclonal antibodies raised by different immunogens assessed, the action of Verticillium fungicola on Agaricus bisporus hyphae examined, and the efficacy of Fusarium tumidum isolates with biocontrol potential against gorse and broom compared. A long-fruiting population of Morchella conica is documented, and numerous isolates of nematophagous fungi have been found in sheep faeces in Brazil. The following new scientific names are introduced: Hebeloma radicosoides, Ramularia byrsonimatis , and Rhizosphaera pseudotsugae spp. nov.; and Pseudocercospora byrsonimatis (syn. Cercospora byrsonimatis ) comb. nov.

The hyphal wall protects the pressurized cell against lysis, physical abrasion, chemical damage, and probably from other microorganisms and predatory invertebrates. Against these assets we can hypothesize costs for a cell that are associated with a wall. For example, phagocytosis is impossible, and the release of secreted molecules is complicated by the diffusional challenge presented by the mesh of microfibrils and interleaving wall polymers. A more controversial idea is that once delimited by a tough integument, growth becomes dependent upon the exertion of internal force to cause wall yielding, and most mycologists have posited turgor pressure as the origin of this force. In relation to growth then, it seems logical to suggest that fungal walls evolved to meet a multitude of needs, and that once a cell became walled, osmosis would automatically generate the turgor it required for growth.

Temperature measurements from the spore-producing gills, spines, and tubes underneath fruit-body caps revealed cooling in 18 basidiomycete species growing in mixed deciduous woodland. The temperature of cultured fruit bodies of Lentinula edodes and Pleurotus ostreatus fell upon exposure to low velocity airflow, consistent with an evaporative mechanism of cooling. The mechanism of ballistospore discharge characteristic of basidiomycete fungi is dependent on condensation of water from the air surrounding the spores onto the spore surface. The current model for this process predicts that condensation, and therefore spore discharge, is enhanced by cooling of the fruit body.

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The distinctive shapes of basidiomata in the bird's nest fungi reflect differences in the mechanism of splash discharge. In the present study, peridiole discharge was examined in Nidularia pulvinata using high-speed video. Nidularia pulvinata produces globose basidiomata that split open at maturity to expose 100 or more peridioles within a gelatinous matrix. Each peridiole contains an estimated 7 million spores. The impact of water drops splashed the peridioles horizontally from the fruit body, along with globs of mucilage, at a mean velocity of 1.2 m s−1. Discharged peridioles travelled for a maximum horizontal distance of 1.5 cm. This launch process contrasts with the faster vertical splashes of peridioles over distances of up to one metre from the flute-shaped fruit bodies of bird's nest fungi in the genera Crucibulum and Cyathus. Peridioles in these genera are equipped with a funicular cord that attaches them to vegetation, placing them in an ideal location for ingestion by browsing herbivores. The absence of cords in N. pulvinata and its use of a sloppy discharge mechanism suggest that it is more likely to be dispersed by animals feeding on the forest floor.

The bird's nest fungi (Basidiomycota, Agaricales) package millions of spores into peridioles that are splashed from their basidiomata by the impact of raindrops. In this study we report new information on the discharge mechanism in Crucibulum and Cyathus species revealed with high-speed video. Peridioles were ejected at speeds of 1–5 m per second utilizing less than 2 % of the kinetic energy in falling raindrops. Raindrops that hit the rim of the basidiome were most effective at ejecting peridioles. The mean angle of ejection varied from 67 to 73° and the peridioles travelled over an estimated maximum horizontal distance of 1 m. Each peridiole carried a cord or funiculus that remained in a condensed form during flight. The cord unravelled when its adhesive surface stuck to a surrounding obstacle and acted as a brake that quickly reduced the velocity of the projectile. In nature, this elaborate mechanism tethers peridioles to vegetation in a perfect location for browsing by herbivores.

The use of molecular bar-coding and consensus on nomenclatural practices has encouraged optimism about the future of fungal taxonomy and systematics. There are, however, profound deficiencies in our understanding of fungal diversity and broader problems with the taxonomic enterprise that deserve greater attention. For 250 years mycologists have tried to reconcile fungal diversity with the Linnean fantasy of a divine order throughout nature that included unambiguous species. This effort has failed and today's taxonomy rests on an unstable philosophical foundation. Rather than persisting with the present endeavour, it may be more fruitful to abandon the notion of fungal species pending further basic research. In the meantime, mycologists should consider tagging collections with digital codes and assigning these operational taxonomic units to higher taxonomic ranks whose objective reality is corroborated by strong phylogenetic evidence.

Osmotic pressures (II) of aqueous solutions of polyethylene glycols (PEGs) of average relative molecular weight (M(r)) between 200 and 10,000 were measured using vapor pressure deficit osmometry. The relationships between molarity and II were described with high precision by second order polynomials for each of the PEGs studied. In contrast to previous reports, equivalent weights of different polymers in solution did not generate the same II; low M(r) PEGs generated a higher II than the higher M(r) PEGs. The effect of PEGs upon II represents an interaction between concentration and M(r).