Blue roundhead

Appearance

Fruitbodies have conical to flattened caps measuring 2–7.5 cm in diameter. They usually have a low, broad umbo. The colour of the cap depends on its age, ranging from pale blue-green to yellowish-bluish green. There is often a whitish zone around the margin, which invariably has bluish-green tints. When moist, the cap is sticky with a cuticle that may be readily peeled; dry caps are smooth and shiny. Gills are initially pale purplish-brown, becoming darker brown in age as the spores mature. They have an adnate or sinuate attachment to the stipe. The stipe has a short-lived annular zone; above this zone the stipe is smooth, while below it is fibrous and scaly. The flesh is colourless, although it may have tinges of blue in the cap and stipe, and lacks any distinctive odour or flavour. "Stropharia cyanea" fruit bodies are not edible.

The spore print is brown. Spores typically measure 8.0–9.0 by 4.0–5.5 µm, and have an ellipsoid to oblong to ovoid shape, depending on the viewing angle. Basidia are narrowly club-shaped, four-spored, and have dimensions of 24–40 by 7–12 µm. The cheilochrysocystidia are club-shaped, measuring 30–55 by 4–40 µm, with a neck that is 2–5 µm wide. Pleurochrysocystidia are 40–60 by 5–18 µm with a 2–4 µm-wide neck. Clamp connections are abundant in all tissues of "S. caerulea". The fungus produces acanthocytes, which are spiny cells produced on short branches on the mycelium.

Naming

There are a few greenish "Stropharia" with which "S. caerulea" might be confused. "Stropharia pseudocyanea" is an uncommon species that grows in meadows. It has a more slender form than "S. caerulea", a soft, spongy stipe, and flesh with an odour similar to fresh pepper. Microscopically, it has a dense palisade of slender, capitate non-staining cheilocystidia on the gill edge. This gives the gills of young, fresh fruit bodies a whitish edge, a feature that is absent from "S. caerulea". Another lookalike, "S. aeruginosa", is less common than "S. caerulea". It is distinguished from the latter by the well-developed ring zone on its stipe, darker gills with white edges, and more numerous whitish scales around the cap margin. Additionally, "S. aeruginosa" has more stable colours than "S. caerulea", the colouration of which tends to quickly wash out. However, collections of "Stropharia" often show characteristics that are intermediate between two or more species, making them difficult to identify accurately.

Distribution

"Stropharia caerulea" is a saprophytic fungus that fruits singly or in groups. It grows in or on meadows, roadsides, hedgerows, gardens, and woodchip mulch. In Europe it is often found in beech woods in alkaline soil. It is a common species found throughout Europe, where it fruits from July to November. Although also found in North America, generally fruiting from August to October, the full extent of its distribution there is unknown.

Fruitbodies of "Stropharia caerulea" form mycelial cords–rootlike structures consisting of a dense mass of hyphae–which create extensive underground networks that move nutrients and allow the fungus to "forage" for resources. These cords are often associated with stems and rhizomes of the common nettle. These mycelial systems' development and the species's interactions with other cord-forming wood decomposer basidiomycetes have been investigated. The mycelia of "Stropharia caerulea" form a fractal structure characterized by a dense, relatively slowly extending front, a formation associated with finding relatively homogeneously distributed nutrients–equivalent to short-range foraging. An increase in the supply of soil nitrogen or phosphorus increases the fractal branching of the mycelia, allowing increased uptake of nutrients.

Habitat

"Stropharia caerulea" is a saprophytic fungus that fruits singly or in groups. It grows in or on meadows, roadsides, hedgerows, gardens, and woodchip mulch. In Europe it is often found in beech woods in alkaline soil. It is a common species found throughout Europe, where it fruits from July to November. Although also found in North America, generally fruiting from August to October, the full extent of its distribution there is unknown.

Fruitbodies of "Stropharia caerulea" form mycelial cords–rootlike structures consisting of a dense mass of hyphae–which create extensive underground networks that move nutrients and allow the fungus to "forage" for resources. These cords are often associated with stems and rhizomes of the common nettle. These mycelial systems' development and the species's interactions with other cord-forming wood decomposer basidiomycetes have been investigated. The mycelia of "Stropharia caerulea" form a fractal structure characterized by a dense, relatively slowly extending front, a formation associated with finding relatively homogeneously distributed nutrients–equivalent to short-range foraging. An increase in the supply of soil nitrogen or phosphorus increases the fractal branching of the mycelia, allowing increased uptake of nutrients.