Destroying Angel

Destroying Angel is a common name applied to a small group of all-white Amanita species in section Phalloideae. In eastern North America the name most often refers to Amanita bisporigera; on the Pacific coast to Amanita ocreata; and in Europe to Amanita virosa. All are white from cap to stem base, all have free white gills, a membranous ring and a well-developed sac-like volva, and all produce a white spore print with amyloid spores.

The group is defined by what it lacks as much as by what it has. There are no loose warts on the cap, no colour in the gills, no bruising reactions in the flesh, and no dark tones anywhere. This uniform whiteness, combined with a tall slender build and a distinctly bagged base, gives the fruiting bodies an eerily clean, almost sculptural appearance among leaf litter.

Amanita bisporigera takes its epithet from its two-spored basidia, an unusual feature in the genus where four spores per basidium is the norm. Its cap surface also turns bright yellow when a drop of potassium hydroxide is applied, a chemical spot test used to separate it from several other white Amanitas.

Cap

4-12 cm across, at first an elongated egg or bullet shape, then convex and finally flat with a low broad umbo. The surface is pure white, sometimes with a faint cream or ivory tint at the very centre, smooth, silky, dry to slightly tacky when wet, and free of loose veil patches. The margin is even and not grooved, distinguishing it from many of the smaller white Amanitas that have strongly striate margins.

Gills

Free from the stem, crowded, narrow to moderately broad, pure white and remaining so throughout the life of the fruiting body, with finely floccose edges. Numerous short gills are interspersed.

Stipe

6-15 cm tall and 0.7-1.8 cm thick, white, dry, often finely fibrillose-shaggy or slightly scurfy on the surface, tapering upward from a swollen base. A soft white membranous ring hangs skirt-like from the upper stem and can collapse or tear away in wet weather. The base sits in a conspicuous white membranous sac with a loose free rim, often buried and easily lost if the stem is pulled rather than dug.

Flesh & spore print

Flesh white throughout, unchanging when cut or bruised. Smell faint and slightly sweet when young, becoming unpleasant with age. Spore print white; spores globose to subglobose and amyloid. In A. bisporigera the cap surface turns chrome yellow with potassium hydroxide solution, a useful supporting character.

Amanita bisporigera is ectomycorrhizal and grows in mixed and broadleaf woodland across eastern and central North America, most often with oak and other hardwoods, occasionally with conifers. It fruits solitarily or in small scattered groups on soil among leaf litter, from early summer through autumn, following warm humid spells.

The related European Amanita virosa favours birch, spruce and pine on acid soils in northern and montane woodland, fruiting from midsummer into autumn, while the western North American Amanita ocreata associates chiefly with coast live oak and other Quercus species and fruits in the mild wet months from late winter into spring, an unusual season for a Phalloideae Amanita.

Like other members of section Phalloideae these fungi form ectomycorrhizas, wrapping the short roots of their host trees in a fungal sheath and penetrating between root cells to form a Hartig net. Mineral nutrients and water move from fungus to tree, and photosynthate moves the other way. The mycelium persists in the soil year after year, producing fruiting bodies only when moisture and temperature conditions align.

Because the association is obligate, distribution mirrors the distribution of host trees very closely, and populations tend to be patchy at the scale of individual woodlands. The fruiting bodies decay rapidly, are colonised by fly larvae and moulds, and contribute to nutrient turnover in the litter layer.

Amanita virosa and Amanita ocreata are the European and western North American counterparts and are separated mainly by range, host trees, season and microscopic detail rather than by field appearance; A. virosa tends to have a more asymmetrically leaning cap and a shaggier stem. Amanita phalloides in its rare all-white form has the same volva and ring but usually retains a faint olive or cream tone at the cap centre and has a stouter, less slender build.

White Agaricus species such as Agaricus arvensis have free gills and a ring but their gills pass from pale pink to chocolate-brown, they give a dark brown spore print, and there is no volva at the base. Lepiota and Leucoagaricus species share a white spore print and a ring but have scaly or granular rather than smooth caps and no sac at the base. Young unopened Destroying Angels look like small white puffballs until sliced vertically, when the outline of an embryonic cap, gills and stem is visible inside a solid puffball's uniform white interior.