Terence Ingold, one of the most influential mycologists of the twentieth century, died in Northumberland, UK, on 31 May at the inspiring age of 104. His researches spanned more than 70 years, and there have been few, if any, individuals who have made a more significant impact on the appreciation of fungi by the wider scientific community. In the 1930s he discovered a ubiquitous but previously overlooked group of aquatic fungi, later called the Ingoldian hyphomycetes. But he is probably better known for his lifelong interest in mechanisms of spore dispersal.

Credit: T. INGOLD

Ingold began his laboratory investigations on fungi in 1926, as an undergraduate at Queen's University in Belfast. Doctoral work at London's Royal College of Science, now part of Imperial College London, was followed by lectureships at the universities of Reading and Leicester, and (in 1944) by a chair at Birkbeck College, University of London.

Ingold's study of aquatic fungi began in 1938 with his analysis of water samples taken from a brook that ran close to his home north of Leicester. The spores of some of these fungi assume beautiful shapes, many with the form of stars or crescents, which collide with drowning leaf fragments that serve as their food. They become rafted on the surface of air bubbles, and may escape into the air. When Ingold presented his discovery at a meeting in Cambridge, UK, one smart alec countered that he had simply misidentified some leaf hairs. The folly of this pronouncement is proven by continuing international research on the diversity and ecology of these microorganisms. Beyond their abundance in streams, Ingoldians have been found in rainwater run-off from buildings, in melting snow and ice, and in plant tissues, in which they may be active symbionts rather than agents of decay.

But Ingold's first mycological love was for the biophysical, in the form of the parade of graceful propulsion mechanisms that have evolved among the fungi. Examples include the hydrostatic guns that squirt spore-containing sporangia skyward above streams of pressurized fluid, and the remarkable process used by spores to jump from mushroom gills. He revelled in these phenomena, drawing on a keen knowledge of physics to advance a discipline more often associated with the non-experimental cataloguing of new species.

The mushroom mechanism was the trickiest he tackled. It had perplexed mycologists since its description in the nineteenth century and had fascinated another great experimentalist, A. H. Reginald Buller (1874–1944). Ingold studied the process for decades and designed some of the crucial experiments that demonstrated that it operates as a kind of catapult energized by surface tension. The artillery fungus, Sphaerobolus stellatus, was another of his favourites, with its spectacular snap-buckling mechanism that shoots a pinhead-sized sporangium over a distance of 6 metres. Many of his experiments on spore movements seemed inspired by Heath Robinson (or Rube Goldberg, for US readers), and included the study of cultures in a hyperbaric chamber and readings from a 'spore clock' whose face became spattered with discharged spores. But these contraptions were highly effective in providing insights into the way that fungi work. By deciphering the physics of spore discharge processes, Ingold helped other researchers to elucidate the complex relationships between weather conditions and the spread of epidemic plant diseases and mould-based allergies.

Ingold's first book, Spore Discharge in Land Plants (1939), which was more mycological than botanical, was followed by a half-dozen exclusively fungal titles written, primarily, for students. His Fungal Spores: Their Liberation and Dispersal (1971) was a masterly guide to the field, and is one of the classic books most likely to be found on the bookshelves of mycologists and plant pathologists throughout the world. In recent days, I have been ruminating on the fact that this book was published as a sort of mid-career offering when he was 66 years old. He continued to study the fungi for another 30 years.

Ingold's sense of humour was apparent through his published cartoons of fungi. But he did not come from the stand-up-comedian school of scientific educators, and was a deeply thoughtful man. Following his retirement in 1972, he loved to walk the country lanes around his home in Oxfordshire and ponder questions about fungi, and life in general. During these years, he studied fungi in a home laboratory and published numerous papers concerning fungal development and spore discharge. As a student, I joined him on some of his strolls, imbibing fragments of knowledge from a gentleman who knew the name of every plant and fungus, and could add an anecdote about each organism's biology. I would be reduced to nodding in silent acquiescence, hoping he would be kind enough to defer testing my knowledge. Yet for a man who lived so long and knew so much, his advice to the neophyte was limited. When I asked him for tips for matching his vigorous longevity, he uttered one unhelpful word: “Genes.”

Terence Ingold was characteristically humble about the significance of his scientific contributions. He confessed regret that he had not spent more time in the laboratory, having instead invested much of his energy on administrative tasks. But colleagues in Britain and abroad benefited greatly from his distraction from the fungi. He kept his department in London running during the final months of the Second World War. And he travelled widely in the 1950s and 1960s as a representative of the University of London, assisting in the development of higher education in countries that had obtained independence from Britain. He was particularly influential in the foundation, in 1966, of the University of Botswana, Lesotho and Swaziland, which offered a regional alternative to education in South Africa during the apartheid era.

He made time for mycological investigations during many of these journeys, and claimed that, if he were “transported to a part of the world without knowledge of its locality”, he could “make a very rough guess as to its latitude by examining the spora of a suitable stream”. In small ways in the lab, and in a larger manner in Africa, he made the world a more interesting place.