Underland: A Deep Time Journey

by Robert Macfarlane

During his second season on the island, Merlin became interested in a type of plants called ‘mycoheterotrophs’ – ‘mycohets’ for short. Mycohets are plants that lack chlorophyll and thus are unable to photosynthesize. As such they are entirely reliant on the fungal network for their provision of carbon. Some are white, some tinged lilac or violet. ‘These little ghosts plug into the fungal network,’ Merlin explains, ‘and somehow derive everything from it without paying anything back, at least in the usual coin. They don’t play by the normal rules of symbiosis – but we can’t prove they’re parasites. You could imagine them as the hackers of the wood wide web.’ Merlin focused on a genus of mycohets called the Voyria, a group of gentians known as ‘ghost plants’, the flowers of which studded the jungle floor on Barro Colorado Island like pale purple stars. Working with local villagers, he carried out a painstaking census of the soil in a series of plots, sampling and sequencing the DNA of hundreds of root samples taken both from green plants and the Voyria. The census allowed him to determine what species of fungi were connecting with which plants – and thereby to make an unprecedentedly detailed map of the jungle’s social network. ‘I only stumbled across the importance of Voyria by accident,’ he says, ‘wandering around one day looking for something else, when I realized that they had almost vanished from a plot where we’d increased the phosphorus input. That’s how my breakthroug...