Common stinkhorn
Mature common stinkhorns are morphologically and olfactorily distinctive fungi that are commonly found in temperate regions of Europe and North America. For much of the year the fungus lives as a network of fine threads and cord-like strands (rhizomorphs) in leaf mould on forest floors or just below soil surfaces. In late summer and autumn, white or pinkish balls, about the size of a hen's egg, with a firm, spongy texture are seen. Their sudden appearance has led people to give them supernatural names such as 'devils' eggs'.
When the 'egg' matures, the fruit body breaks through the outer skin, which remains as a cup (volva) at the base of the stalk. The mature fungus has a thin, conical, honeycomb-like cap borne on top of a thick, spongy stalk that can be up to 20 centimetres long. When it first emerges, the cap is covered with a green-brown, sweetish-tasting, spore-filled slime (gleba) that is very attractive to carrion-feeding flies. Unlike most cap-forming fungi, where spores are carried by the wind, in stinkhorns the spores are mainly dispersed by insects. Slugs may also have a role in the local dispersal of stinkhorn spores.
Inside the 'egg', the cap, gleba and stalk of the fungus are already formed. Consequently, when enough water is available, cell expansion means that the emergence of the mature fungus is rapid (1-15 centimetres per hour) and noisy; the eighteenth-century French botanist Pierre Bulliard likened the sound to that of a 'pistol shot'. The morphology of the mature fungus led the Swedish botanist Carolus Linnaeus to give an obvious generic name, whilst the species epithet means 'without shame'. Unsurprisingly, through the Doctrine of Signatures, numerous European cultures have associated the fungus with aphrodisiacs. In some countries, stinkhorn 'eggs' are eaten as delicacies.
Robert Plot, the late seventeenth-century Keeper of the Ashmolean Museum, described the stinkhorn as sending 'forth that filthy stink, by the help whereof they are commonly found'. The 'filthy stink', emitted by the gleba and attractive to flies, is due to the presence of a rich cocktail of sulphur-containing compounds such a methyl sulphide and methanethiol.
Ecologically, stinkhorns are part of the community of saprophytes that decompose and recycle dead plants. One of the important plant nutrients that stinkhorns move through landscapes, using their rhizomorph network, is phosphate. Stinkhorns are also important habitats for distinctive groups of flies that are adapted to life feeding on fungi.
Further reading
Courtney SP et al. 1990. Ecology of mushroom-feeding Drosophilidae. Advances in Ecological Research 20: 225-274.
Johnson SD and Jurgens A 2010. Convergent evolution of carrion and faecal scent mimicry in fly-pollinated angiosperm flowers and a stinkhorn fungus. South African Journal of Botany 76: 796-807.
Niksic M et al. 2004. Is Phallus impudicus a mycological giant? Mycologist 18: 21-22.
Stephen Harris