A few fungi can be smelled before they are seen. A walk through the woods in the late summer is often enlivened by a stench that proves a stinker is nearby. This can set the party to work to find the source of the aroma, which often takes a surprisingly long time. Lurking behind a tree or beneath the scrub, the culprit will be identified, resembling a white candle rising from the litter: a stinkhorn.
Stinkhorns are the most sexually explicit fruit body. The Latin name is Phallus impudicus,[1] which tells you all you want to know. The white stem of the stinkhorn arises from a pallid ‘scrotal’ bag to a foot in height or sometimes more, its penile qualities further emphasised by the glans-like cap atop the stem. When it is freshly arisen a greenish slime covers this cap. Those who discover it for the first time tend to express clearly their involuntary reaction to such a blatant object. A closer look allows fascination to take over. A search among the nearby leaf litter often discovers a white sphere – a little larger than a golf ball – tucked in at the top of the soil. This is the stinkhorn ‘egg’. Prodded with the finger there is a certain rubberiness to its texture – there is no ‘shell’ to this egg, but rather a flexible white membrane surrounding it. Inside is a greenish jelly around a ‘bud’ that will expand into another malodorous phalloid. I have watched the process at work. Over the course of a day the bag of the egg is ruptured as the thrusting stem rises to its full glory. The white stem is quite unlike that of most mushrooms: a hollow centre is surrounded by a sponge-like, fragile network full of small holes – if anything, it reminds me of a brandy snap.
The slime on the ‘cap’ includes an extraordinarily rich brew of chemicals that might otherwise be found in excrement or rotting meat. This is not so much a cocktail as a witches’ brew of pungent rot and shit; the word ‘putrid’ could have been coined to describe a mélange of more than two dozen volatile substances that otherwise belong with decaying carcasses and faeces. Since our deficient human sense of smell can detect the stinkhorn from some distance, it is not surprising that flies quickly discover this bonanza thanks to the exquisitely tuned organelles on their antennae. To them, stinkhorn must seem like the smell of the Christmas turkey rolled up with that of freshly baked bread. It summons them from who-knows-where. I have observed flies with their little sucker pads at work on the green slime, sucking at it with enthusiasm. However, they do not lay their eggs on the fungus as they would on a carcass of a dead mouse. Instead they seem to use the green gleba as food. They polish it off. When they have finished their work the stinkhorn remains behind as a white wand, and the ‘cap’ is revealed as conical, pale and coarsely netted without its glutinous covering. At this stage the pong is much reduced – indeed, it almost has a sweet component. The stinkhorn has done its work.
That work is the distribution of its spores. Stinkhorn spores are minute even by fungal standards, a few thousandths of a millimetre long and only one or two thousandths of a millimetre wide. To see them under the microscope, it is necessary to rack up the magnification to the point where the oil immersion lens must be brought into play. Now they look like tiny beans, yet each spore includes the capacity to generate a new Phallus. A fly may seem small, but compared with the size of a stinkhorn spore it is a monster. The fly’s intestinal system is cavernous. As the insect flies onwards around the woodland it excretes the stinkhorn spores in tiny droppings. A very few of these may be lucky enough to land in exactly the right place for germination; and if a spore does germinate maybe it will be fortunate enough to encounter just the right kind of organic material for its life as a saprotroph. The stinkhorn’s strategy may be seen as trading on luck, but its strange habits probably give it an edge over a hundred other fungus species that don’t recruit a fly as an ally. Sooner or later a new stinkhorn will establish its mycelium. The mycelial ‘roots’ of Phallus can be found by gently scraping in the soil around an egg. It is more easily seen than that of other fungi, as it forms rather substantial white threads, resembling coarse cotton, which seek out new food among the leaf litter. If you pick up an egg the cords hang off the bottom, as if unwilling to let go of a stray leaf.
There is a second, scarcer Phallus species in Britain. It is only found in sand dunes in our islands, but is apparently more catholic in its tastes elsewhere in the world. Near Holkham in Norfolk, the Sand Stinkhorn (Phallus hadriani) regularly appears in the hollows between dunes that have become stabilised by coarse marram grass away from the seashore. The white mycelial cords seek out the decaying grass entrained beneath the surface sand. Even at an early stage the uncommon stinkhorn is distinguished readily enough from its common relative by having a pinkish-coloured egg. Whether the smell also differs is controversial. The pioneer British mycologist Reverend Miles Berkeley even described it as having a sweet smell of violets, or perhaps irises. It still seems to attract flies and small beetles, which appear as if by magic when the stinkhorn ‘erupts’. Other accounts recognise an unpleasant odour not unlike that of its cousin.
When I eventually found this species in its natural habitat, much of its slime had already been consumed by insects, and in the Norfolk wind the odour was not particularly unpleasant – but then the regular stinkhorn is much less noisome after the flies have been at work. I had assumed that the species name might have related to Emperor Hadrian, builder of the eponymous wall, although his connection to stinkhorns was unclear to me. The real reason is more curious. The fungus was first named and described by a Dutchman with the Latinised name Hadrianus Junius, as early as 1564, from sand dunes in Holland. It thus is not only one of the first fungi to be described (and the origin of the name Phallus), but was actually named before the much commoner stinkhorn of woods and copses. Hadrian’s Phallus led the way.
It may seem unlikely that stinkhorns have any use as food. I have seen dried Phallus species on sale in China, in a shop decorated with all manner of exotic plants and anonymous things in jars, where it was doubtless part of their vast traditional pharmacopeia. At the egg stage, however, the ‘nut’ inside is reported as edible because the smelly component only develops when the fruit body has expanded. My foraying friend Stuart demonstrated this to appropriate effect, after showing a small party of naturalists the adult in flagrante to induce a proper measure of awe. After demonstrating the egg phase, he neatly cut it open to show the ‘nut’ in place, pushed it out and popped it into his mouth to an accompaniment of horrified gasps. It had, he declared, a nice crunchy texture and a nutty taste. I doubt he made many converts.
A commoner, smaller species is the Dog Stinkhorn (Mutinus caninus), which does indeed resemble the genital equipment of a male canine, with a red tapering tip that shows through once the brownish gleba has been consumed. It would have to be a rather small dog. Like its larger cousin, it arises from eggs – smaller, and more elongate than those of the stinkhorn. These are occasionally found in ‘clutches’, concealed among damp leaf litter in most kinds of woodland. It is rather a feeble phalloid, with the pinkish spongy stem usually not much thicker than a pencil, and often flopping over. The smell is fetid, although it hardly matches that of Phallus impudicus, but is enough to ensure the attention of flies.
A decade ago I was approached by a neighbour in my small hometown in Oxfordshire who thought some kind of alien had landed in his garden. Several extraordinary structures had appeared at the back of his flowerbeds. They were bright red in colour, so they could not fail to attract attention. He thought they looked as if they had fallen from the sky rather than erupted from the ground. About the size of a small grapefruit, the structures were a sort of cage constructed of corrugated coloured struts that joined together to make a small number of polygons. They were quite fragile, so a strut could be severed with the poke of a stick. The fungus suggestion occurred to him simply because nothing else seemed to fit the weirdness of this bizarre organic production – if it is strange enough it must belong to that eldritch kingdom! It could have been something from an H.P. Lovecraft story (who also loved the word ‘eldritch’). ‘When I saw how weird it was,’ he said, somewhat unflatteringly, ‘I thought of you.’ I was relieved he did not mention the obtrusive smell.
However, I did establish that the ‘structures’ had emerged from a slightly irregular white sac – the remains of the egg. It was indeed another phalloid, and one that is apparently becoming commoner in the United Kingdom. I had recently seen it in the gardens of a palazzo by Lake Como in Italy, and I had heard reports of it from Hampshire. The database for British fungi has scattered records, and it is frequent in the Isle of Wight in some years. Now here it was in Oxfordshire. It may be one of those species that is becoming more frequent with the warming of our climate, although John Ramsbottom noted British records of this distinctive fungus as early as the mid nineteenth century, and it may well be native to our islands. By any measure it is an extraordinary production, appropriately called the Red Cage Fungus (Clathrus ruber). It, too, has malodorous spore-carrying slime on its surface to attract flies. I convinced my neighbour that he was extremely fortunate to have such a visitor next to his compost heap, but it did not turn up again the following year. Fungi are never biddable.
Clathrus species provide an interesting test case for thinking about what is native and what is introduced. An even more extraordinary species than the Red Cage Fungus is Clathrus archeri (formerly known as Anthurus archeri) that rejoices in two alternative common names: Devil’s Fingers or Octopus Stinkhorn. Both names have something to be said for them. The first impression made by this fungus is of a lurid red, stranded sea creature with spread-eagled arms. An octopus is appropriate (although fewer than eight arms are usually present), but it could equally well be a starfish. In either case it looks most inappropriate arising from a mossy bank in the middle of Oxfordshire, which is where I found it in 2022. It is a startling thing to discover. When something so anomalous appears apparently from nowhere, it is perhaps not so surprising that the devil himself is invoked – so here are his fingers. By now, we will know what to expect of a phalloid, and once again we find that originally all-enclosing bag and the fetid slime spread on the ‘fingers’ of the fruit body that insects find so irresistible. It is not so difficult to see how this relates to Clathrus ruber either, since the ‘fingers’ of this fungus are at first conjoined into the beginnings of a cage. It is such a distinctive species that it must have attracted attention wherever it turned up. It is known to be a native of New Zealand and Australia, from where the Reverend Berkeley originally described it in 1859. It seems to have arrived in England close to the beginning of the First World War; perhaps the spores were carried on the boots of an Anzac soldier recruited from the wilds of Tasmania. Unlike some invaders, and in spite of its name, the Devil’s Fingers seems to have done no damage upon its arrival, but is here to surprise and delight us with its alien form.
The phalloid fungi are probably the most fantastical of all the fungi that produce spores on basidia (Basidiomycetes). Many of them are tropical, or originated from the southern hemisphere. A review of these fungi published in 2021 recognised twenty-two different genera of which only three are regularly found in Britain. They span a spectrum of size and colours, some with pallid ‘arms’ raised like gothic arches, others looking like coarsely crumpled paper, a few almost agaric-like in proportions; all arising from ‘eggs’ and attracting flies. In Australia I saw stinkhorns that were orange in colour covering whole flowerbeds in a park in Adelaide; they were more spectacular than any of the flowers nearby. Some stinkhorns (Phallus indusiatus) have what can only be described as a perfectly lacy dress hanging down below the cap – a ‘garment’ whose shape resembles the skirts of Turkish whirling dervishes. It is a structure without parallel in the natural world. I saw these wonderful fungi while I was working in Thailand; they were lurking in the shadows of a bamboo forest. They seemed to be a kind of hallucination, too extravagant to be true. This must have been the same species as the dried packets on sale in the Chinese herb shop, since they are the only phalloids to have culinary and medical applications. The American diplomat Henry Kissinger was served them on a mission to China in the early 1980s but he was, perhaps, rather an unlikely candidate to be vulnerable to their alleged hallucinatory properties.
Another extraordinary antipodean species has rarely been recorded as an ‘escape’ in Britain, the Starfish Fungus (Aseroe rubra), which looks remarkably like a scarlet sea anemone on a contrasting white stalk, arising from compost heaps or rich soil. It has a spectacular radial array of ‘tentacles’ spread out symmetrically, often splitting into two towards their tips, and the brownish, smelly gleba lies at the centre. In cooler climates this spectacular phalloid has been found in greenhouses, but the practice of mulching flowerbeds with woodchips and organic matter may encourage it outdoors. Wherever it grows it is likely to attract attention and amazement at the inventiveness of the fungal kingdom.
The phalloids demonstrate a successful variation on the saprotrophic lifestyle, and have evolved concomitantly special designs, although it is hardly possible to guess why some species should find making a cage or a ‘starfish’ an advantage in the circus of life. You might imagine that a fly is unlikely to be concerned with the architecture of the fruit body, only with the tastiness of the lunch provided. Can it be that recruiting insect partners somehow teases out the inventiveness of natural selection? Among the flowering plants those species that have adopted flies as pollination agents are also often spectacular: the parasitic Corpse Lily Rafflesia from Sumatra not only has the largest flower in the world, but has also ‘created’ the stench of rotting flesh to attract its pollinators. The small succulent Stapelia has disproportionately large flowers with a similarly unpleasant odour, and at least one species produces blossoms very like starfish, inviting a comparison with Clathrus archeri. There is even a preference for reddish colours in these flowers – suggesting meat perhaps?
Plants and fungi have been on separate evolutionary pathways for more than a billion years, but can still contrive similar complex tricks to hoodwink invertebrate animals that have been on yet a third trajectory through unimaginable stretches of geological time. History weaves patterns, and these patterns can be recruited across the great kingdoms of life. It could be argued that the fungi have been most successful of all in subverting the senses of insects for their own ends. Stinkhorns and their allies are probably more widely distributed around the world than any of the flowering plants that have devised comparable tricks. Creeping unseen through the forest floor, these fungi are masters of deception, weirdly dressed as starfish or dervishes.